application of lean manufacturing principles to construction

Transcription

APPLICATION OF LEAN
MANUFACTURING PRINCIPLES TO
CONSTRUCTION
by
James E. Diekmann, Mark Krewedl, Joshua Balonick,
Travis Stewart, and Spencer Won
A Report to
The Construction Industry Institute
The University of Texas at Austin
Under the Guidance of
Project Team Number 191
Austin, Texas
July 2004
Executive Summary
Over the past three decades, the US construction industry has seen a decline in both its share of
the gross national product and its annual productivity growth rate. The quality of construction
has faltered during this period as well. In contrast, the US manufacturing industry has made
significant progress in increasing productivity and product quality while lowering product lead
times. Manufacturing has essentially made the transition from second class to world class.
The improvements in manufacturing processes have included reducing the amount of human
effort, space and inventory required in the factory and increasing the quality and variety of
products and the flexibility of manufacturing operations. The application of “lean production”
principles to manufacturing processes has been instrumental in achieving these results. Lean
principles were developed in post–World War II Japan at the Toyota Motor Company. These
principles evolved from geographic and economic constraints, from top-down, management-led
innovation and from bottom-up pragmatic problem solving. They became collectively known as
the Toyota Production System (Womack et al. 1990).
The principles of lean theory are conceptualized at the process, project and enterprise or
organization levels. Various principles, methods and tools can be applied at each level, so that
lean production becomes an inclusive philosophy aimed at continuously improving the entire
production organization as well as the physical production process.
If manufacturing can make such vast improvements in quality and productivity, while reducing
costs and lead times, why not construction? This report identifies the core principles of lean
production, compares and contrasts the manufacturing and construction industries, and identifies
the potential for implementing lean principles in the construction industry.
The research team started with the following definition of lean construction:
Lean construction is the continuous process of eliminating waste, meeting or
exceeding all customer requirements, focusing on the entire value stream and
pursuing perfection in the execution of a constructed project.
This definition includes many fundamental aspects of a lean philosophy. It is a philosophy that
requires a continuous improvement effort that is focused on a value stream defined in terms of the
needs of the customer. Improvement is, in part, accomplished by eliminating waste in the
process.
Lean philosophy, broadly defined, can apply to design, procurement and production functions.
To help define and direct research efforts and to present an elemental contribution to
understanding lean principles in construction, the scope of this report was limited primarily to
construction field operations. Although the focus of the inquiry was field operations, researchers
were sensitive to the effects of policy and actions that occur at the enterprise, project and process
levels. Two considerations led the research team to focus primary attention on construction field
operations. First, field operations are where most of the value is added from the customer’s point
of view. Cognizance of customer value is central to a lean philosophy. Second, other researchers
have studied value streams and other aspects of lean philosophy.
iii
From this basis, the following questions were developed:
•
Are lean principles as defined in manufacturing applicable to the construction
industry? If not, are there other principles that are more appropriate for
construction?
•
What is the nature of the typical construction production value stream?
•
How should conformance to lean principles be measured?
•
Are lean principles commonly used in the construction industry?
•
What is the path forward to becoming lean?
•
What are the roadblocks to adopting a lean culture?
These questions were investigated using a multifaceted approach. First, lean literature was
examined from manufacturing, construction and other industries such as shipbuilding, aerospace,
and software engineering. Second, advice from lean manufacturing pioneers was used, and the
construction production value stream was studied. Next, contractors (both lean and non-lean)
were surveyed to learn about lean practices that are currently employed in the construction
industry.
Using all of this information, a set of lean principles was developed that is appropriate for
construction. In general, it can be concluded that construction owners and contractors would
significantly benefit from the adoption of lean principles and behaviors. The value added portion
of the typical field construction value stream is exceedingly small, comprising approximately
10 percent of all crew level activities. It was determined that lean behavior among construction
contractors is rare, even with contractors who are actively pursuing the lean ideal, because being
truly lean requires changes to every aspect and level of a company. Additionally, becoming a
lean contractor is difficult in part because of the dynamic nature of construction, but mostly
because construction contractors control such a small portion of the construction value stream.
For those wishing to start the lean journey in their company, a lean workplace can be created
using the following steps:
•
Identify waste in field operations.
•
Drive out waste.
•
Standardize the workplace.
•
Develop a lean culture.
•
Involve the client.
•
Continuously improve.
iv
Becoming lean is a long-term, comprehensive commitment; it amounts to a cultural change for
the company. Construction is no simple deterministic system. Lean principles must be
understood and applied in a context and require a comprehensive understanding of a complex,
interacting and uncertain construction system. Many lean principles can be understood as
attempts to increase preplanning ability, improve organizational design and increase flexibility.
In this light, the final conclusion is that lean cannot be reduced to a set of rules or tools. It must
be approached as a system of thinking and behavior that is shared throughout the value stream.
Given that contractors control such a small portion of the construction value stream (as compared
to their manufacturing counterparts), this is the challenge that faces the potential lean contractor.
If successfully applied, however, lean has the potential to improve the cost structure, value
attitudes and delivery times of the construction industry.
v
Contents
Executive Summary ....................................................................................................................... iii
1.0
Introduction ........................................................................................................................ 1
1.1
Are Lean Manufacturing Principles Useful in Construction? ............................... 1
1.2
History of Lean Production ................................................................................... 1
1.3
The Diffusion of Lean Ideas.................................................................................. 5
1.4
Research Questions ............................................................................................... 5
1.5
Organization of Report.......................................................................................... 7
2.0
Lean Theory and Literature ................................................................................................ 8
2.1
Predominant Types of Manufacturing in the 20th Century: Conversion
Model Versus Flow Model.................................................................................... 8
2.2
Fundamental Lean Principles .............................................................................. 12
2.3
Beyond Lean Manufacturing............................................................................... 16
3.0
Differences Between Construction and Manufacturing ................................................... 25
3.1
Lean Principles .................................................................................................... 25
3.2
Core Manufacturing Lean Principles................................................................... 25
3.3
Core Construction Lean Principles...................................................................... 27
3.4
Comparison of Construction and Manufacturing ................................................ 27
4.0
Research Methodology..................................................................................................... 34
4.1
Restatement of Research Questions .................................................................... 34
4.2
Developing Lean Principles for Construction ..................................................... 34
4.2.1
Goals.....................................................................................................34
4.2.2
Approach ..............................................................................................34
4.3
Measuring Lean Conformance ............................................................................ 35
4.3.1
Goals.....................................................................................................35
4.3.2
Approach ..............................................................................................35
4.4
Value Stream Mapping........................................................................................ 38
4.5
Bringing It Together............................................................................................ 39
5.0
Creation and Use of a Lean Assessment Instrument ........................................................ 41
5.1
Foundation/Design of the Questions ................................................................... 41
5.2
Design of the Questionnaire Using Field Studies................................................ 43
5.3
Case Study Interviews ......................................................................................... 44
5.4
Early Adopter Interviews .................................................................................... 44
5.5
Validation of the Questionnaire .......................................................................... 45
5.5.1
Stage One: Pilot Work .........................................................................45
5.5.2
Stage Two: Focus Group Responses ...................................................45
5.5.3
Stage Three: Statistical Reliability Analysis .......................................46
5.6
Use of Lean Principles in Construction............................................................... 47
5.6.1
Customer Focus ....................................................................................47
5.6.2
Culture/People ......................................................................................49
5.6.3
Workplace Standardization...................................................................49
5.6.4
Waste Elimination ................................................................................49
5.6.5
Continuous Improvement/Built-In Quality...........................................49
vi
Contents (Continued)
5.7
5.8
5.9
6.0
Case Study Interview Results.............................................................................. 50
5.7.1
Customer Focus ....................................................................................50
5.7.2
Culture/People ......................................................................................50
5.7.3
5.7.4
5.7.5
Early Adopter Interview Results ......................................................................... 51
5.8.1
Customer Focus ....................................................................................51
5.8.2
Culture/People ......................................................................................52
5.8.3
5.8.4
5.8.5
Survey of Lean Implementation in Construction Literature................................ 53
5.9.1
Lean Implementation Case Studies at the Process Level......................53
5.9.2
Lean Implementation Case Studies at the Project Level ......................55
5.9.3
Lean Implementation Case Studies at the Organization Level.............57
Evaluating a Construction Value Stream ......................................................................... 59
6.1
Construction’s Production Value Stream ............................................................ 59
6.2
Categories of Work ............................................................................................. 59
6.2.1
VA Definition .......................................................................................59
6.2.2
NVAR Definition .................................................................................59
6.2.3
NVA (Waste Definitions) .....................................................................60
6.3
Data Collection Procedure................................................................................... 61
6.3.1
Hand Data Collection Method ..............................................................61
6.3.2
Video Data Collection ..........................................................................64
6.4
Case Studies ........................................................................................................ 64
6.4.1
Case Study No. 1 ..................................................................................64
6.4.2
Case Study No. 2 ..................................................................................64
6.4.3
Case Study No. 3 ..................................................................................66
6.4.4
Case Study No. 4 ..................................................................................66
6.4.5
Case Study No. 5 ..................................................................................66
6.4.6
Case Study No. 6 ..................................................................................66
6.4.7
Data Analysis........................................................................................66
6.5
Value Stream Analysis Results ........................................................................... 69
6.5.1
Structural Steel Case Studies ................................................................70
6.5.2
Process Piping Case Studies .................................................................73
6.5.3
Comparison of Processes......................................................................75
6.5.4
Value Stream Analysis .........................................................................76
6.6
Identifying Construction’s Value Stream............................................................ 76
6.7
Developing a Construction Value Stream Map................................................... 77
6.8
Building a Value Stream Map ............................................................................. 77
6.9
New Approach to Value Stream Mapping .......................................................... 78
6.9.1
Level Three...........................................................................................78
6.9.2
Level Two.............................................................................................82
6.9.3
Level One .............................................................................................84
6.10
New Idea for Displaying the Construction Value Stream ................................... 87
6.11
How Do the Value Stream Maps Differ Between Processes?............................. 90
vii
Contents (Continued)
7.0
Results - Lean Principles for Construction....................................................................... 91
7.1
Assessing Lean Principles for Construction........................................................ 91
7.1.1
Customer Focus ....................................................................................92
7.1.2
Culture/People ......................................................................................95
7.1.3
Workplace Organization/Standardization.............................................98
7.1.4
Waste Elimination (Aspect 1: Process Optimization) .......................101
7.1.5
Waste Elimination (Aspect 2: Supply Chain)....................................106
7.1.6
Waste Elimination (Aspect 3: Production Scheduling) .....................106
7.1.7
Waste Elimination (Aspect 4: Product Optimization) .......................110
7.1.8
Continuous Improvement and Built-In Quality ..................................112
7.2
An Information-Based Perspective on Lean Principles..................................... 115
7.3
Applying Lean Principles to Construction ........................................................ 117
8.0
Conclusions and Recommendations............................................................................... 121
8.1
Reasons to Apply Lean Principles to Construction........................................... 121
8.2
Path Forward to Becoming Lean....................................................................... 121
8.2.1
Identify Waste in Field Operations.....................................................121
8.2.2
Drive Out the Waste ...........................................................................122
8.2.3
Standardize the Workplace .................................................................122
8.2.4
Develop a Lean Culture ......................................................................122
8.2.5
Get the Client Involved with the Lean Transformation ......................122
8.2.6
Continuously Improve ........................................................................122
8.3
Barriers to Developing a Lean Company .......................................................... 122
8.3.1
Little General Understanding of Lean ................................................123
8.3.2
Unique Projects and Unique Design...................................................123
8.3.3
Lack of Steady-State Conditions ........................................................123
8.3.4
No Control of the Entire Value Stream ..............................................123
8.4
Future Research................................................................................................. 123
8.4.1
Lean Coordination ..............................................................................123
8.4.2
Economics of Lean .............................................................................124
8.4.3
Importance of Repetition ....................................................................124
8.4.4
Reliability in Construction..................................................................124
8.4.5
Metrics for Lean Construction............................................................124
Appendix A
Appendix B
Appendix C
Appendix D
Appendix E
Appendix F
Appendix G
Appendix H
Appendix I
Appendix J
Case Study No.1 - Structural Steel .................................................................... 125
Case Study No. 2 - Structural Steel ................................................................... 152
Case Study No. 3 - Structural Steel ................................................................... 192
Case Study No. 4 - Process Piping .................................................................... 227
Lean Questionnaire and Principle Cross-Reference.......................................... 277
Interview Notes ................................................................................................. 285
Worker Movement Study No. 1 ........................................................................ 300
Worker Movement Study No. 2 ........................................................................ 308
References ................................................................................................................................... 313
Glossary....................................................................................................................................... 318
Acknowledgments ....................................................................................................................... 325
viii
List of Tables
Table 2.1
Table 2.2
Table 3.1
Table 3.2
Table 5.1
Table 6.1
Table 6.2
Table 6.3
Table 6.4
Table 6.5
Table 6.6
Table 6.7
Table 6.8
Table 6.9
Table 6.10
Table 6.11
Table 6.12
Table 6.13
Table 6.14
Table 6.15
Table 6.16
Table 7.1
Table 7.2
Table 7.3
Comparison of the Conversion Model and Flow Model ......................................11
Knowledge Areas of Management Theories ........................................................19
Comparison of Lean Manufacturing to Lean Construction Principles.................28
Lean Construction Principles ...............................................................................32
Cronbach’s Alpha Results ....................................................................................48
Comparison of Lean Manufacturing to Lean Construction Waste.......................62
Advantages and Disadvantages of Different Data Collection Methods ...............65
Typical Results for Welder Completing an Eight Inch Diameter Spool
Section..................................................................................................................67
Typical Results for an Entire Crew ......................................................................68
Results for Case Study No.1 - Structural Steel Erection Process.........................70
Quick Summary for Case Study No. 1 .................................................................70
Results for Case Study No. 2 - Structural Steel Erection Process........................71
Results for Case Study No. 3 - Structural Steel Erection Process........................71
Results for Case Study No. 4 - Piping Installation Process..................................73
Result for Case Study No. 5 - Piping Installation Process ...................................74
Comparison of Different Processes ......................................................................75
Work Distribution Lifecycle Data ........................................................................89
Principles that Reduce Uncertainty in the Production Environment
without Increased Planning or Information Handling ........................................118
Principles that Require Added Planning or Information Handling but
Reduce Uncertainty in the Production Environment..........................................119
Principles that Require Added Planning or Information Handling but
Reduce the Negative Effects of Instability in Production ..................................120
x
List of Figures
Figure 1.1
Figure 1.2
Figure 2.1
Figure 2.2
Figure 2.3
Figure 2.4
Figure 2.5
Figure 2.6
Figure 2.7
Figure 4.1
Figure 4.2
Figure 5.1
Figure 6.1
Figure 6.2
Figure 6.3
Figure 6.4
Figure 6.5
Figure 6.6
Figure 6.7
Figure 6.8
Figure 6.9
Figure 6.10
Figure 6.11
Manufacturing Performance (Anecdotal)...............................................................2
The Beginnings of Lean Production.......................................................................4
Conversion Process ................................................................................................8
The Conversion Model of Production ....................................................................8
Generalized Flow Model ......................................................................................10
Simplified Value Stream ......................................................................................10
The Flow Model of Production ............................................................................10
Delineation of Activities ......................................................................................12
Lean Production Conceptualization .....................................................................17
Overall Lean Construction Research Plan............................................................36
The Lean Wheel (after Tapping, Luyster et al. 2002) ..........................................37
Example of a Seven-Point Likert Scale Question ................................................42
Hand Data Collection Sheet .................................................................................63
Typical Results for Welder Completing an Eight Inch Diameter Spool
Section..................................................................................................................68
Typical Results for an Entire Crew ......................................................................69
Traditional Value Stream Map .............................................................................79
Structure for a New Value Stream Map ...............................................................80
Level Three Data ..................................................................................................81
Level Two ............................................................................................................82
Typical Setup for a Substage Box in the Value Stream .......................................82
Main Stage from Level One Along with Required Substages from
Level Two ............................................................................................................83
Level One .............................................................................................................86
Work Distribution Life Cycle Graph....................................................................88
xii
1.0 Introduction
1.1 Are Lean Manufacturing Principles Useful in Construction?
Over the past three decades, the US construction industry has seen a decline in both its share of
the gross national product and its annual productivity growth rate. The quality of construction
has faltered during this period as well, with studies showing the cost of construction
nonconformance reaching as high as 12 percent of total project costs (Koskela 1992). In contrast,
the US manufacturing industry has made significant progress in increasing productivity and
product quality while lowering product lead times:
How have manufacturing organizations achieved the following results?
•
Half the amount of human effort required in the factory.
•
Half the manufacturing space required.
•
Half the engineering hours to develop a new product.
•
Less than half the inventory needed onsite.
•
Increased quality of products.
•
Increased variety of products.
•
Increased flexibility of manufacturing operations.
•
Decreased lead times.
(Womack et al. 1990)
The application of lean production principles to manufacturing processes has been instrumental in
achieving these results. This report explores whether these same principles may be applied to
construction processes to effect similar production improvements.
1.2 History of Lean Production
Over the past three decades, US manufacturing has seen a resurgence in quality, flexibility and
productivity, while also managing to lower product lead times and the cost of production. In
other words, US manufacturing has made the transition from second class to world class
(Schonberger 1996). According to Richard J. Schonberger, World Class Manufacturing: The
Next Decade, much of this rebirth has been the result of an increased focus on production cycle
times and quality. Subsequently, manufacturing management has seen a shift from conventional
practices of planning and control to a focus on interactive sets of principles aimed at achieving
and facilitating benefits, such as lower cycle times. Figure 1.1 (adapted from Schonberger 1996)
illustrates the described performance trend in US manufacturing over the last half of the 20th
century.
1
Figure 1.1: Manufacturing Performance (Anecdotal)
Schonberger provides the “v-pattern” to illustrate the fall and rise of US manufacturing
performance caused by both internal and external factors. The figure is not a direct depiction of
economic indicators, but rather a representation of anecdotal evidence (Schonberger 1996). The
negative trend seen between the 1950s and 1970s occurred at a time when manufacturing in the
United States was just coming out of what is known as the post–World War II production era. At
this time, product shortages within the United States increased demand and, subsequently,
manufacturing was focused on producing large quantities of products. When supply had finally
surpassed demand, the nation began to see the proliferation of excess capacity. During the early
1960s, international competition also began to increase its share of the world manufacturing
market. With the immediate threats of excess capacity and foreign competition, the focus of
manufacturing in the United States needed to change from producing volume to producing higher
quality products at minimal cost and lead times. But how was the United States going to change
from large-scale mass production pioneered by the late Henry Ford to more agile, customerfocused production?
The answer to this question has been the diffusion of Japan’s highly successful production and
management system termed “lean production” (Womack et al. 1990). The term was coined by
John Krafcik, a researcher on the team from the International Motor Vehicle Program (IMVP)
(Womack et al. 1990). IMVP was a team organized at the Massachusetts Institute of Technology
during the mid-1980s with the objective of studying the innovative techniques used by the
Japanese in their highly successful automotive industry (Womack et al. 1990). The logic of using
the term “lean” will become clearer as the principles are clarified. The fundamental ideas of lean
production have been described under numerous names as researchers and practicing
professionals have sought to study and diffuse the core ideas. Names such as World Class
Manufacturing (Schonberger 1997), New Production Philosophy (Koskela 1992), Lean Thinking
(Womack and Jones 1996), Just-in-Time/Total Quality Control, Time Based Competition, and
many similar methods and principles have been used to describe the same fundamental collection
of ideas (Koskela 1992).
The foundations of lean production were developed in post–World War II Japan, when the
Japanese manufacturing industry underwent a complete rebuilding (Womack et al. 1990). Lean
pioneers Kiichiro Toyoda, Eiji Toyoda and Taiichi Ohno of the Toyota Motor Company
developed many of the underlying principles of lean production in response to pragmatic
considerations and existing geographic circumstances. The impetus for lean production occurred
when Kiichiro, president of Toyota at the time, demanded that Toyota “…catch up with America
in three years. Otherwise the automobile industry of Japan will not survive” (Ohno 1988; Hopp
2
1996). At the time, limited supply of raw materials and inadequate space for inventory in Japan
fostered an atmosphere in which concepts such as just-in-time (JIT) and zero inventories became
necessary. During the spring of 1950, Eiji Toyoda visited American manufacturers, namely
Ford’s Rouge Plant in Detroit, to study mass production and perhaps look for ways to improve
the country’s own rebuilding industry (Womack et al. 1990). This was the second visit to study
US manufacturing practices made by the Toyoda family; the first was made by Kiichiro in 1929.
What Eiji Toyoda found was a system rampant with muda, a Japanese term that encompasses
waste (Womack 1996). He noted that only the worker on the assembly line was adding value to
the process. Another striking feature was the emphasis placed by their American counterparts on
continually running the production line. This common practice was thought to be justified by the
expense of purchasing such equipment. To the Japanese, this practice appeared to compound and
multiply errors, a mistake the Japanese could not afford to make.
Japan’s labor productivity at the time was one ninth that of the United States, and it became
obvious to Toyota that it could not compete with the United States by depending on economies of
scale to produce massive volumes for a small market that did not have the same type of demand
(Ohno 1988; Shingo 1981; Hopp 1996). Toyota then made the strategic decision to focus its
manufacturing efforts not on massive volumes of a product but, rather, on many different
products in smaller volumes. In his numerous experiments focused on reducing machine setup
times, Ohno, Toyota’s chief production engineer, noted that the cost of producing smaller batches
of parts was less than that of producing larger quantities as practiced in the United States. This
was true because making small lot sizes greatly reduced the carrying costs required for huge
inventories, and the cost of rework was reduced because defects showed up instantly in smaller
batches (Womack et al. 1990). Ohno also managed to reduce the amount of time required for
machine setup from an entire day to three minutes, a task that enabled Toyota to increase the
flexibility of its production lines as well as reduce production times. The concept of JIT was
developed to complement this new production philosophy undertaken at Toyota. The model for
JIT was the American supermarket, a relatively new idea to the Japanese in the 1950s (Hopp
1996). The American supermarket provided customers with what they needed, when they needed
it and in the right amount needed. JIT further evolved to include concepts found to be crucial to
the effective operation of the JIT system and that would later become goals of the system. These
concepts are referred to as the seven zeros: zero defects, zero lot size, zero setups, zero
breakdowns, zero handling, zero lead time and zero surging (Hopp 1996).
The contributions of quality pioneer W. Edwards Deming to post–World War II Japan altered the
way Japanese manufacturers viewed quality. Deming’s Total Quality Management (TQM)
system permeated throughout organizations to create a quality culture, where quality became the
primary goal of producers. After World War II, quality had taken a back seat to production, and
it was reasoned that intensive inspection at the end of the process would be adequate. With its
focus on the entire organization, TQM addressed issues that were relatively new to the
manufacturing industry at that time, such as employee empowerment, continuous improvement
and the concept of proactively building quality into products versus the reactive nature of
inspecting for quality at the end of the process (Walton 1986). The Japanese would improve on
the teachings of Deming and create what is known as Total Quality Control (TQC). Thus,
coupled with the company’s move toward multi-skilled teams, guarantees of lifetime employment
and pay raises linked only to seniority within the company, Toyota began to create a culture in
which the quality of its product improved dramatically. In addition to shifting the focus of
Japanese manufacturers to quality, Deming also equipped them with the statistical tools to
achieve it, such as Statistical Quality Control (SQC). The teachings of Deming and other quality
gurus, such as Joseph Juran and Philip Crosby, fueled a quality movement within the Japanese
manufacturing industry that would take decades to diffuse into mainstream Western
3
manufacturing and that would be highly influential to the development of lean production
techniques.
From this background, the Toyota Production System was created in the early 1960s through the
combination of compensation for geographical restrictions, astute observation of current
problems within the industry, development of JIT and the teachings of the quality movement,
among other factors. It seems that postwar Japan, in its state of chaos, provided a perfect
laboratory in which innovative thinking could be implemented and practiced (Womack et al.
1990). The actual process, however, took many years of trial and error. The Toyota Production
System presents an outline of the foundations of lean production. Figure 1.2 illustrates the forces
that influenced the development of lean production.
Post World War II Japan (Toyota Motor Company)
Limited
Natural
Resources
Development
of JIT
Lower
Demand
Limited
Space
Quality
Movement
Mass
Production
Practices
Additional
Factors
Beginnings of Lean
Production
Figure 1.2: The Beginnings of Lean Production
In the late 1970s, this new production system was brought to the United States and contributed to
a manufacturing renaissance that continued within the United States for the next three decades
(Schonberger 1996). Studies have shown the incredible benefits lean production methods have
brought specifically to the automobile manufacturing industry where the ideas originated.
According to James P. Womack and Daniel T. Jones, two of the leading researchers of lean
production systems and coauthors of numerous lean texts such as The Machine That Changed the
World and Lean Thinking, lean automobile manufacturing has been characterized as using the
following:
…half the human effort in the factory, half the manufacturing space, half the
investment in tools, half the engineering hours to develop a new product in half
the time. Also, it requires keeping far less than half the needed inventory on site,
results in many fewer defects, and produces a greater and ever growing variety of
products (Womack et al. 1990).
The visible success of lean principles in the automobile industry and in manufacturing generally
has prompted other industries to adapt and apply these concepts to achieve similar benefits.
4
1.3 The Diffusion of Lean Ideas
Lean principles have been amended and expanded over the decades by those in other industries
who are transferring lean ideas and successes to their respective industries. The software,
aerospace, air travel and shipbuilding industries all have extensive efforts directed at applying
lean principles to improve profitability and quality and reduce waste.
The architecture, engineering and construction (AEC) industry has a far-reaching, worldwide
effort to apply lean principles and practices. North America, Europe and South America have
organizations devoted exclusively to studying lean ideas and applying them. In fact, the efforts of
the AEC industry have led the way toward innovative ideas about the application of lean thinking
to the construction industry. Koskela (1992, 2000) originated the idea that construction processes
must be viewed as systems of transformations, flows and value adding actions, the so-called TFV
model. Bertelsen (2002) expanded the manufacturing model of lean to include the ideas of
construction as one-of-a-kind production, construction as a complex system and construction as
cooperation. Ballard and Howell (1998) in their paper, “What Kind of Production is
Construction,” describe differences between manufacturing and construction. In the United
Kingdom, the Construction Task Force produced “Rethinking Construction” (The Egan Report)
that applies the lessons of the manufacturing revolution to the construction sector in the United
Kingdom. Another innovation in the application of lean theory to construction was the
development of the Last Planner (Ballard 2000a) that emphasizes reliability in the planning
function. Others (Matthews 2003; Ballard 2002c; Tommelein 2003; dos Santos 1999) have
addressed the impact that lean principles have had on contracts, project delivery and project
supply chains.
In this way, the core idea of lean principles as originally set forth by Ohno was expanded and
adapted throughout the manufacturing sector. Other management thinkers have coupled diverse
management theories such as concurrent engineering and TQM to these core lean principles.
“Lean theory” and “lean applications” for AEC design, procurement and production functions
have received significant attention in many quarters around the world.
1.4 Research Questions
The goal of the research team was to take what is already known about lean theory and practice
from manufacturing and from construction’s early adopters and distill that information into a
straightforward set of lean principles for construction. The research team started with the
following definition of lean construction:
Lean construction is the continuous process of eliminating waste, meeting or
exceeding all customer requirements, focusing on the entire value stream and
pursuing perfection in the execution of a constructed project.
This definition includes many fundamental aspects of a lean philosophy:
•
Lean requires a continuous improvement effort.
•
Improvement focuses on a value stream that is defined in terms of the needs of
the customer.
•
Improvement is, in part, accomplished by eliminating waste in the process.
5
A lean philosophy, broadly defined, can apply to design, procurement and production functions.
Lean can apply to the enterprise or company level, to the project level and to the individual
process level.
To help define and direct research efforts and to present an elemental contribution to the
understanding of lean principles in construction, the scope of this report was limited primarily to
construction field operations. Though the focus of the inquiry was field operations, researchers
were sensitive to the effects of policy and actions that occur at the enterprise, project and process
levels. Two considerations led the research team to focus its primary attention on construction
field operations. First, field operations are where most of the value is added from the customer’s
point of view, so cognizance of customer value is central to a lean philosophy. Second, others
have studied various aspects of lean philosophy, and this information could be used as a
foundation for this report. For example, Seymour (1996) and Ballard (2000c) have defined an
agenda for lean construction across the entire project life. Arbulu (2002), Tommelein (2003) and
London (2001) have addressed construction supply chains. Likewise, aspects of the design
process to promote lean principles are discussed by Ballard (2000d), Koskela (1997) and Freire
(2002), who have all addressed different aspects of lean design.
Taking into consideration the history of lean principles and prior research, the following question
was posed:
•
construction?
To explore how manufacturing principles map to the construction process, these questions were
defined:
•
What is nature of the typical construction production value stream?
•
What is the value stream for field production activities and for the field portion of
material delivery and handling?
After an understanding is gained about how lean principles apply or can be modified for
construction, these questions may be addressed:
•
•
Finally, to benefit the Construction Industry Institute (CII) membership, the following two
questions were considered:
•
•
6
1.5 Organization of Report
This report is organized into eight chapters and 10 appendices. Chapter 2 presents a
comprehensive review of both manufacturing and construction literature on lean principles.
Chapter 3 explores the differences between the manufacturing and construction domains.
Chapter 4 describes the methodology used for this study. Chapter 5 describes the development of
a questionnaire that can be used by a contractor to self-assess lean behavior. Chapter 6 describes
the results of the value stream mapping studies. Chapter 7 communicates the study findings
regarding lean principles for construction. Finally, Chapter 8 describes research team
recommendations for the future of lean principles in construction. The appendices contain the
details of each of the value stream case studies as well as information on the validation of the
questionnaire and questionnaire interview notes. Additionally, the appendices contain two
studies on the impacts of excess worker movement.
7
2.0 Lean Theory and Literature
2.1 Predominant Types of Manufacturing in the
20th Century: Conversion Model Versus Flow Model
To fully understand lean production, it is important to become familiar with the two predominant
types of production systems of the 20th century. Traditionally, US manufacturing has been
viewed as a mass production system focusing primarily on the process of conversions (Koskela
1992). Figure 2.1 (adapted from Figure 3, Koskela 2000) illustrates this basic concept.
Figure 2.1: Conversion Process
The conventional breakdown of the manufacturing process into a series of activities, each
undertaking the conversion of an input to an output, referred to as the conversion model or
transformation model, is illustrated on Figure 2.2 (adapted from Rother 1998). This type of
production system historically uses what is called a batch and queue theory (Womack 1996).
Batch and queue refers to the theory that for machines to achieve a high utilization rate, they must
be run continually. As a result of this, parts are manufactured in large batches at one process
within a plant and then queued for the next process. Batch and queue theory leads to many
manufacturing problems, such as bottlenecking and large inventories from high work-in-progress
(WIP) levels.
Figure 2.2: The Conversion Model of Production
The inventories created by WIP are referred to in manufacturing as buffers (Womack 1996).
Buffers generally reduce the variability of workflows within a plant by shielding downstream
activities from uncertainties that might occur upstream, such as machine failure or differing
machine output rates. Such buffers may be the result of WIP or even planned into the
8
manufacturing process. Buffers can be viewed as an advantage if high degrees of variability exist
within the manufacturing process. Disadvantages associated with overbuffering include
increased product lead times, increases in required working capital, as well as increased space
requirements to produce and store the additional parts and components acting as the buffers. By
using such queuing techniques, manufacturers also become susceptible to quick changes in the
marketplace. For example, if demand in the market for a certain product decreases, the
manufacturer may be caught with high levels of WIP acting as buffers and be forced to decide
whether it would be financially feasible to complete the production of the product or to terminate
production and scrap the partially completed work.
The concept of manufacturing a product based on forecasted sales data and then selling it is
referred to as “push” production (Womack 1996). This differs greatly from the idea of producing
an item only when it has been ordered or purchased, which is “pull” production. In other words,
the market for the product is pulling the production versus pushing the product out to the
customer. The view of manufacturing as a process of conversions tends to emphasize push
production. Thus, products are created because demand has been forecasted and then pushed
onto the market.
The conversion model of production views improvement of the production process as a
subprocess task. For example, to improve the process on Figure 2.2, the producer would make
efforts to improve each subprocess individually by either reducing the cost of the specific activity
and/or by increasing the efficiency of the activity. Thus, in theory, by improving each activity
(A, B, C), the entire conversion process will improve. This view is termed “reductionist” because
it uses analytical reduction to break the process into its individual components and view each as a
separate entity in need of improvement (Koskela 1992). Historically, improvements to the
conversion model have focused on the implementation of new technologies such as automation
and computerization (Koskela 1992).
In their book, The Machine That Changed the World, James P. Womack, Daniel T. Jones and
Daniel Roos provide an excellent descriptive summary of the typical mass producer:
The mass producer uses narrowly skilled professionals to design products made
by unskilled or semiskilled workers tending expensive, single-purpose machines.
These churn out standardized products in very high volume. Because the
machinery costs so much and is so intolerant of disruption, the mass producer
adds many buffers – extra supplies, extra workers, and extra space to assure
smooth production. Because changing over to a new product costs even more,
the mass producer keeps standard designs in production for as long as possible.
The result: The consumer gets lower costs but at the expense of variety and by
means of work methods that most employees find boring and dispiriting
(Womack et al. 1990).
The view of production as a series of conversions is fundamentally different from the second
dominant type of production in the 20th century, the view of manufacturing as a flow model
(Koskela 1992). Production as a flow process is one of the core ideas of lean production.
Figure 2.3 (adapted from Rother 1998) represents a generalized flow model of production.
9
Figure 2.3: Generalized Flow Model
Unlike the traditional view of production, the flow process does not view the production stream
solely as a series of conversions. The conceptualization of manufacturing as a flow model
delineates between those activities that add value to the process (conversion) and those that do
not (Koskela refers to them as flow activities) (Koskela 1992). It should be noted that to avoid
confusion about flow, this report will refer to activities that do not add value as non-value adding.
By defining the different types of activities that occur in production, the focus of improvement
does not become compartmentalized as on Figure 2.2, but rather envelops the entire value stream
(Womack 1996). The value stream of a particular product consists of all activities and parties
involved in its creation, from raw material suppliers to the customer as illustrated on Figure 2.4.
Compartmentalized improvements can become troublesome to downstream activities if the
particular cycle times of sequential operations are not matched. In other words, if Process A has
half the cycle time of Process B, a material buffer will occur at Process B because it cannot keep
up with the amount of work produced by Process A.
Figure 2.4: Simplified Value Stream
Examples of non-value adding activities, or muda, are large inventories, wait times, inspection
time, WIP and overproduction (Womack 1996). Improvement to the system would then entail
not only reducing the cost and improving the efficiency of the value adding activities, but also
reducing and/or eliminating the non-value adding activities. Figure 2.5 (adapted from Koskela
2000) illustrates these concepts.
Figure 2.5: The Flow Model of Production
10
Improving the system through waste elimination and conversion activity improvement allows all
elements of the entire production process to be enhanced.
The flow process tends to focus on the elimination of the large buffers found within mass
manufacturing by emphasizing the constant movement of components from one value adding
activity to the next. This type of system, also referred to as single-piece flow (Womack 1996), is
associated with several benefits. First, the WIP levels are dramatically reduced, which also
reduces the inventory space required as well as the capital to produce and stock extra inventories
of partially completed products. Combined with reducing equipment setup times, low WIP levels
can help a manufacturer become more responsive to market conditions. As a result, the producer
lets the customer, or market, pull the production.
Compared to the conversion model, flow operations are much more tightly controlled in terms of
production times and supply chain coordination to minimize variability within the process. In
fact, the introduction of time as an input to the production process is fundamentally different from
the conversion model of production because the process is no longer conceptualized as solely an
economic abstraction, but rather as a physical process (Koskela 1992). Time was considered
important before the advent of the flow model, but the entire production system was not centered
on time as a goal. This view of time is important because the flow process does not contain the
buffers necessary to minimize variability within the manufacturing process and, therefore, must
rely on the coordination of processes both internal and external to the plant. Table 2.1 and
Figure 2.6 summarize the major differences between the two predominant production theories of
the 20th century.
Table 2.1: Comparison of the Conversion Model and Flow Model
Description
Conversion Model
Flow Model
Conceptualization
Manufacturing as a series of conversion
activities
Manufacturing as a combination of
value and non-value adding
activities
Basic Queuing Theory
Batch and queue
Single-piece flow
Inventory Implications
Large inventories as a result of batch
and queue production and WIP
Minimal inventories
Production Trigger
Products pushed onto the market as a
result of forecasted demand
Products pulled onto the market by
demand
Focus on Improvement
Improvement focused on lowering cost
and increasing productivity of each
activity (analytical reductionism)
Improvement focused on lowering
cost and increasing productivity of
value adding activities and
reducing/eliminating non-value
adding activities
Variability Control
Buffers used to control variability
Use of coordination among internal
operations as well as supply chain
management to reduce variability
Focus of Control
Cost and time of activities
Cost, time and value of value
adding and non-value adding
activities
11
Figure 2.6: Delineation of Activities
2.2 Fundamental Lean Principles
The work of Lauri Koskela has yielded the following list of principles believed to be crucial to
lean production:
•
Meeting the Requirements of the Customer. Attention must be paid to quality
as defined by the requirements of the customer. The success of production
hinges on the satisfaction of the customer. A practical approach to this is to
define the customers for each stage and analyze their requirements.
•
Reducing Non-Value Adding Activities. Non-value adding activities generally
result from one of three sources: the structure of the production system, which
determines the physical flow that is traversed by material and information; the
manner in which the production system is controlled; and the nature of the
production system such as defects, machine breakdowns and accidents.
•
Reducing Cycle Time. Cycle time is defined as the total time required for a
particular piece of material to traverse the flow. Cycle time can be represented as
follows:
Cycle Time= Processing Time +Inspection Time +Wait Time +Move Time
Research has identified the following activities that reduce cycle time:
−
Eliminating WIP.
−
Reducing batch sizes.
−
Changing plant layout so that moving distances are minimized.
−
Keeping things moving; smoothing and synchronizing flows.
−
Reducing variability.
−
Isolating the main value adding sequence from support work.
−
Changing activities from sequential to parallel ordering.
−
Solving problems caused by constraints slowing down material flow.
12
•
•
Reducing Variability. Variability of activity duration increases the volume of
non-value adding activities. It may be shown through queuing theory that
variability increases cycle time. Variability reduction is aimed at reducing both
the nonconformance of products as well as duration variability during both value
adding and non-value adding activities. A few strategies aimed at variability
reduction are as follows:
−
Standardization of activities by implementing standard procedures.
−
Mistake-proofing devices (poke yoke).
Increasing Flexibility. The ability of the production line to meet the demands of
the marketplace and change must be increased. Research has recognized the
following activities aimed at increasing output flexibility (Stalk 1990):
−
Minimizing lot sizes to closely match demand.
−
Reducing the difficulty of setups and changeovers.
−
Customizing as late in the process as possible.
−
Training a multi-skilled workforce.
•
Increasing Transparency. The entire flow operation must be made visible and
comprehensible to those involved so that mistakes can be located and solved
quickly.
•
Maintaining Continuous Improvement. The organization must continually
strive to incrementally improve operations and management methods. The
following methods have been classified as necessary for institutionalizing
continuous improvement:
•
−
Measuring and monitoring improvement.
−
Setting stretch targets (e.g., for inventory elimination or cycle time
reduction) by means of which problems can be found and solved.
−
Giving responsibility for improvement to all employees; steady
improvement from every organizational unit should be required and
rewarded.
−
Using standard procedures as hypotheses of best practices, to be
constantly challenged by better ways.
−
Linking improvement to control; improvement should be aimed at the
current control constraints and problems of the process. The goal is to
eliminate the root of problems rather than to cope with their effects.
Simplifying by Minimizing the Number of Steps, Parts, and Linkages.
Complexity produces waste as well as additional costs. When possible, the
process should be streamlined through efforts such as consolidating activities;
13
standardizing parts, tools and materials; and minimizing the amount of control
information needed.
Practical approaches to simplification include the following:
−
Shortening flows by consolidating activities.
−
Reducing the part count of products through design changes or
prefabricated parts.
−
Standardizing parts, materials, tools, etc.
−
Decoupling linkages.
−
Minimizing the amount of control information needed.
•
Focusing Control on the Complete Process. Segmented flow leads to
suboptimization and should be avoided; thus, control should be focused on the
entire process for optimal flow.
•
Balancing Flow Improvement with Conversion Improvement.
Flow
improvement and conversion improvement are interconnected; therefore, their
individual improvements should be analyzed to create balance within the process.
•
Benchmarking.
Benchmarking can provide the stimulus to achieve
breakthrough improvement through radical reconfiguration of processes.
James P. Womack and Robert T. Jones (1996) have identified five fundamental and sequential
steps that create a conceptual outline of what they call “lean thinking.” A quick comparison with
the ideas outlined by Koskela reveals many similarities, as the works of Womack and Jones have
proven to be influential within this particular field of study. The steps are as follows:
•
•
Step 1. Specify value from the standpoint of the customer:
−
Understand the customer.
−
Target cost.
−
Look at the whole.
−
Specify value by product/service.
−
Value must be defined for each product family, along with a target cost
based on the customer’s perception of value.
Step 2. Identify the value stream for each product family:
−
Understanding flow is the key technique for eliminating waste (muda).
−
Create a vision of flow.
14
•
•
•
−
Compete against perfection by eliminating muda.
−
Identify value adding activities.
−
Identify contributory non-value adding but required activities (Type I
muda).
−
Identify non-value adding activities (Type II muda).
−
Rethink operating methods.
−
Eliminate sources or root causes of waste in the value stream.
Step 3. Make the product flow:
−
Focus on actual object from beginning to completion and produce
continuous flow.
−
Ignore traditional boundaries (department).
−
Apply all three of these steps at the same time.
−
Work on the remaining non-value adding activity (Type I muda).
−
Synchronize and align so there is little waiting time for people and
machines.
−
Match workload and capacity.
−
Minimize input variations.
Step 4. Ensure that this happens at the pull of the customer:
−
Communicate.
−
Apply level scheduling.
−
Release resources for delivery just when needed.
−
Practice JIT supply rather than JIT production.
−
Continue to work on the remaining non-value adding activity (Type 1
muda).
Step 5. Manage toward perfection:
−
Increase transparency.
−
Form a picture of perfection.
15
Individually, the principles, methods and techniques have been applied with partial success, but
together, they create a powerful framework and philosophy for improving manufacturing
performance. It is important to realize that this framework affects not only the production
process; it requires a fundamental shift in how an organization thinks about itself. The ideas
behind these principles create the backbone of a lean production environment. The overlap of
ideas from JIT, TQM, Visual Management, Time Based Competition and other manufacturing
methodologies, philosophies and practices are explored in the following sections.
2.3 Beyond Lean Manufacturing
With the basic idea of flow production systems established, it is important to look beyond core
manufacturing ideas to the broader context of “lean.” Figure 2.7 illustrates an example of how
one might conceptualize lean production. First, it might be conceptualized as a grouping of
principles and goals crucial to the operation of a flow system, such as reducing lead times and
variability. Second, it might be conceptualized as a set of methods aimed at facilitating the
principles and goals of flow operations, such as pull scheduling. Third, it might be
conceptualized as a set of tools that aid the methods, such as utilizing Kanban cards to trigger pull
scheduling. The level of detail increases as one views the chart from left to right. Although the
figure does not include all elements of lean production, it does provide a basic outline of the lean
production process.
The ideas of lean can also be conceptualized on the following three levels (Koskela 2000):
1.
Process Level--A set of tools, such as Kanban cards, poke yoke, etc.
2.
Project Level--A production planning method, such as JIT.
3.
Organization Level--General management theory, such as TQM.
Lean implementation may consist of applying lean principles at any of the three levels. A
comprehensive lean implementation will cover all aspects of the business directly related to
production, transport, supply or service activities (dos Santos 1999; Schroeder 1993; Wild 1995).
An examination of several knowledge areas can aid in the understanding of how lean principles
affect the different aspects of a production organization. The knowledge areas of a production
organization can be generalized as follows (Fearon et al. 1979):
1.
Design and Development. Design and development of products and/or services
that meet the needs of customers as well as the needs of the manufacturing
process (manufacturability) is one element of a production organization; it
typically includes product life-cycle analysis, value engineering, product
prototyping, market research and product specification.
16
Figure 2.7: Lean Production Conceptualization
2.
Work Configuration. Work configuration refers to the design of the operating
system for an organization. Location of the facilities, plant layout and work
study are considered the three most important factors when determining a
particular organization’s work configuration.
3.
Scheduling and Planning. This portion of a production organization refers to
the determination of demand for a specific product and the planning of
production as well as the scheduling of resource requirements to meet that
demand.
4.
Quality. Quality in a production organization includes the determination of what
constitutes quality in the process, what relevant costs are linked to quality, how
quality is to be achieved and ensured and what level of quality is desired.
5.
Inventory Management. Inventory management refers to issues such as how
much of a particular item should be produced to replenish stocks as well as how
stocks should be stored and handled.
6.
Human Resources Management. This element of a production organization
concerns how a producer organizes and interacts with its employees. Human
resources management also affects the corporate culture of a company.
17
7.
Supply Chain Management.
Supply chain management involves the
management of internal and external sources of materials, supplies and services
to support operations.
Manufacturing has seen a proliferation of theories directed toward improving different aspects of
production and operations management. Many of these theories share similar fundamental goals
with lean production and, in many cases, were highly influential in the development of lean
principles. It can be difficult to distinguish between overlapping concepts in these theories.
Table 2.2 organizes selected manufacturing theories, methodologies and techniques into the
respective knowledge areas of the production organization to which they apply.
A brief review of the concepts of these methodologies reveals that there is a considerable amount
of overlap that occurs when these movements are compared to the principles identified as crucial
to lean. For example, Time Based Competition (TBC) directly relates to the principle of reducing
lead times, while Visual Management (VM) strives to make the process transparent to those
involved. It can be concluded that lean, as it is understood today, is a conglomeration or
synthesis of many theories, philosophies, methods and techniques, many of which are individual
methodologies within the manufacturing community. The evolution of lean ideas within manufacturing has been a process of trial and error that has incorporated both “top down” (theoretical)
and “bottom up” (pragmatic) problem solving and many of the ideas discussed in Table 2.2.
As a first step toward establishing a set of lean principles for construction, Chapter 3 considers
the similarities and differences between construction and manufacturing.
Chapter 5.0,
Section 5.9, surveys available literature on the implementation of lean principles in construction.
18
Table 2.2: Knowledge Areas of Management Theories
1. Design and Development
A. Concurrent Engineering (CE)
Concurrent (or simultaneous) engineering deals primarily
with the product design phase. The term refers to an
improved design process characterized by rigorous upfront requirements analysis, incorporating the constraints
of subsequent phases into the conceptual phase, and the
tightening of change control toward the end of the design
process. Compression of the design time, increase of the
number of iterations (i.e., increase in the frequency of
information exchange), and reduction of the number of
change orders are three major objectives of CE.
B. Poke Yoke
This is a manufacturing technique for preventing
mistakes by designing the manufacturing process,
equipment and tools so that an operation literally cannot
be performed incorrectly; an attempt to perform
incorrectly, in addition to being prevented, is usually met
with a warning signal of some sort; the term poke yoke is
sometimes used to signify a system where only a warning
is provided.
C. Modular Design
Modular design is organizing a set of distinct components
that can be developed independently and then “plugged
together.”
D. Value Engineering
Value engineering is the systematic application of
recognized techniques by a multidisciplined team to
identify the function of a product or service, establish a
worth for that function, generate alternatives through the
use of creative thinking, and provide the needed functions
to reliably accomplish the original purpose of the project
at the lowest life-cycle cost without sacrificing safety,
necessary quality and environmental attributes of the
project.
E. Standard Work Design
Standard work design is the design of each work activity
specifying cycle time, work sequence of specific tasks
and minimum inventory of parts on hand needed to
conduct the activity.
19
Table 2.2: Knowledge Areas of Management Theories (Continued)
2. Work Configuration
A. Visual Management (VM)
VM is an orientation toward visual control in production,
quality and workplace organization. The goal is to render
both the standard to be applied and a deviation from it as
immediately recognizable by anyone. This is one of the
original JIT ideas that has been systematically applied
only recently in the West.
B. Cellular Manufacturing
Cellular manufacturing is an approach in which
manufacturing work centers (cells) have all the necessary
capabilities to produce an item or a group of similar
items.
C. Flexible Manufacturing
Flexible manufacturing is an integrated manufacturing
capability to produce small numbers of a great variety of
items at a low unit cost. Flexible manufacturing is also
characterized by low changeover time and rapid response
time.
3. Scheduling and Planning
A. Line Balancing
Line balancing is a means of balancing the appropriate
number of workers needed for a production line by
satisfying cycle time and precedence constraints.
B. Just-in-Time (JIT)
JIT is a scheduling philosophy that emphasizes delivery
(when needed) of small lot sizes. JIT includes focusing
on setup cost reduction, small lot sizes, pull systems,
level production and elimination of waste.
C. Critical Path Method/PERT
(CPM/PERT)
CPM/PERT is a method of determining the critical path
by examining the earliest and latest start and finish times
for each activity.
D. Aggregate Planning
Aggregate planning includes the broad, overall decisions
that relate to the programming of resources for
production over an established time horizon.
E. Master Production Schedule
(MPS)
MPS is a time-phased plan specifying the number and the
time frame for building each end item.
F. Distribution Requirements
Planning (DRP)
DRP is the function of determining the need to replenish
inventory at branch warehouses over a period of time.
20
3. Scheduling and Planning (Continued)
G. Queuing Theory
Queuing theory is a branch of mathematics that deals
with understanding systems with customers (orders, calls,
etc.) arriving and being served by one or more servers.
Queuing theory models are usually concerned with
estimating the steady-state performance of the system
such as the utilization, the mean time in queue, the mean
time in system, the mean number in queue and the mean
number in the system.
H. Theory of Constraints (TOC)
TOC is a management philosophy that recognizes that
there are very few critical areas, resources or policies that
truly block the organization from moving forward. If
performance is to be improved, an organization must
identify its constraints, exploit the constraints in the short
run and, in the longer term, find ways to overcome the
constraints (limited resources).
4. Quality
A. Total Quality Management
(TQM)
TQM is an approach for improving quality that involves
all areas of an organization: sales, engineering,
manufacturing, purchasing, etc., with a focus on
employee participation and customer satisfaction. TQM
can involve a variety of quality control and improvement
tools and emphasizes a combination of managerial
principles and statistical tools.
B. Statistical Quality Control (SQC)
SQC uses statistical methods to identify, prioritize and
correct elements of the manufacturing process that detract
from high quality.
C. Taguchi Methods
Taguchi methods were developed to improve the
implementation of TQC in Japan. They are based on the
design of experiments to provide near optimal quality
characteristics for a specific objective. The goal is to
reduce the sensitivity of engineering designs to
uncontrollable factors or noise. This is sometimes
referred to as “robust design” in the United States.
D. ISO 9000
ISO 9000 is a standard that provides an external
motivation to say what you do and do what you
document.
E. Quality Function Deployment
(QFD)
QFD is a method for ensuring that the customer has a
voice in the design specification of a product. QFD uses
inter-functional teams from manufacturing, engineering
and marketing. QFD is the only comprehensive quality
system aimed specifically at satisfying the customer.
21
4. Quality (Continued)
F. Total Quality Control (TQC)
The difference between TQM and TQC is epitomized by
the phrase “management vs. control.” Most companies
“control” quality by a series of inspection processes, but
“managing” quality is a continuous quality improvement
program. However, a good control system is the first step
in the development of a management system.
G. Acceptable Quality Level (AQL)
AQL is a concept that holds that there is some non-zero
level of permissible defects.
H. Six Sigma
Six Sigma is a structured application of the tools and
techniques of TQM on a project basis to achieve strategic
business results. It is sometimes defined as a failure rate
of 3.4 parts per million.
I.
Zero Defects
Zero defects is a concept introduced by Japanese
manufacturers that stresses the elimination of all defects.
This concept contrasts with the idea of AQL.
J.
Quality Circles
Quality circles are teams that meet to discuss quality
improvement issues.
5. Inventory Management
A. Just-in-Time (JIT)
This scheduling philosophy emphasizes delivery when
needed of small lot sizes. JIT includes focusing on setup
cost reduction, small lot sizes, pull systems, level
production and elimination of waste.
B. Material Requirements Planning
(MRP)
MRP is a system to support manufacturing and
fabrication organizations by the timely release of
production and purchase orders using the production plan
for finished goods to determine the materials required to
make the product.
C. Manufacturing Requirements
Planning (MRP II)
MRP II is a method for effective planning of all the
resources of a manufacturing company. Ideally, it
addresses operational planning in units, financial
planning in money, and has a simulation capability to
answer “what-if” questions.
D. Economic Order Quantity (EOQ)
EOQ deals with the optimal order quantity (batch size)
that minimizes the sum of the carrying and ordering cost.
E. Period Order Quantity (POQ)
POQ is a lot sizing rule that defines the order quantity in
terms of the period’s supply.
F. Stock Keeping Unit (SKU)
SKU is a unique identification number (or alphanumeric
string) that defines an item for inventory.
22
6. Human Resources Management
A. Total Quality Management
(TQM)
TQM is a an approach for improving quality that involves
all areas of an organization: sales, engineering,
manufacturing, purchasing, etc., with a focus on
employee participation and customer satisfaction. TQM
can involve a variety of quality control and improvement
tools and emphasizes a combination of managerial
principles and statistical tools.
B. Employee Involvement
Rapid response to problems requires empowerment of
workers. Continuous improvement is heavily dependent
on day-to-day observation and motivation of the
workforce, hence, the idea of quality circles. To avoid
waste associated with division of labor, multiskilled
and/or self-directed teams are established for
product/project/customer based production.
C. Cross Training and Job Rotation
Under this theory, employees are rotated out of their jobs
after a certain duration and trained in new jobs. They are
not only trained how to do the job, but they are also
trained about the quality and maintenance issues that go
along with the job. The principle here is that an
employee with a well-rounded background about how the
company operates will be more valuable to the company
in making improvements.
7. Supply Chain Management
A. Outsourcing
Outsourcing is that practice of procuring raw materials
and components externally rather than creating them
internally.
B. Strategic Partnering
Partnering is a structured management approach to
facilitate teams working across contractual boundaries.
With such coordination, construction companies may
benefit from reductions in delivery times, improved
supplier responsiveness, improved quality of products
and services, as well as reductions in costs.
Miscellaneous
A. Kaizen
Kaizen is the philosophy of continual improvement. This
approach proposes that every process can and should be
continually evaluated and improved in terms of time
required, resources used, resultant quality and other
aspects relative to the process.
B. Kanban
Kanban is a card or sheet used to authorize production or
movement of an item. The quantity authorized per
individual kanban is minimal, ideally one.
23
Miscellaneous (Continued)
C. Total Productive Maintenance
(TPM)
TPM refers to autonomous maintenance of production
machinery by small groups of multiskilled operators.
TPM strives to maximize production output by
maintaining ideal operating conditions.
D. Continuous Improvement
Continuous improvement, associated with JIT and TQC,
has emerged as a theme itself. A key to this approach is
to maintain and improve the working standards through
small, gradual improvements. The inherent wastes in the
process are natural targets for continuous improvement.
The term “learning organization” refers partly to the
capability of maintaining continuous improvement.
E. Benchmarking
Benchmarking refers to comparing one’s current
performance against the world leader in any particular
area. In essence, it means finding and implementing best
practices in the world. Benchmarking is essentially a
goal setting procedure.
F. Time Based Competition (TBC)
TBC refers to compressing time throughout the
organization for competitive benefit. Essentially, this is a
generalization of the JIT philosophy.
G. Value Based Management
(VBM)
VBM refers to conceptualized and clearly articulated
value as the basis for competing. Continuous
improvement to increase customer value is one essential
characteristic of VBM.
H. Re-Engineering
Re-Engineering is the radical reconfiguration of
processes and tasks, especially with respect to
implementation of information technology. Recognizing
and breaking away from outdated rules and fundamental
assumptions is a key issue of re-engineering.
I. Computer-Aided Design/
Computer-Aided Manufacturing
(CAD/CAM)
In this approach, engineering designs may be created and
tested using computer simulations and then transferred
directly to the production floor where machinery uses the
information to perform production functions.
J. Activity-Based Costing
Activity-based costing attempts to collect cost data on all
activities that occur rather than on just the three primary
resources (i.e., materials, labor and machinery). This is
an attempt to define the components of burden. The
objective of this system is to look at all areas where cost
reductions can be implemented.
24
3.0 Differences Between Construction
and Manufacturing
3.1 Lean Principles
The previous chapter clearly establishes the widespread consideration that has been given to the
lean idea in the manufacturing domain. Fujimoto (1999), Womack and Jones (1996), MacInnes
(2002) and others have codified sets of lean principles for manufacturing, some of which are
briefly listed in Section 3.2. The core principles of the concept emanate directly from the Toyota
Production System. However, as application of lean ideas became more prevalent, the
fundamental principles of the Toyota Production System were expanded to incorporate a broader
array of processes, tools and techniques (Schonberger 1996; Plossl 1991).
3.2 Core Manufacturing Lean Principles
Fujimoto (1999) summarizes the essence of the Toyota Production System into the following
three principles:
•
Routinized manufacturing capability--Standard ways of production.
•
Routinized learning capability--Standard ways of problem solving and solution
retention.
•
Evolutionary learning capability--Learning for system change and improvement.
Womack defines the following five principles:
•
Specify value from the standpoint of the customer.
•
Identify the value stream.
•
Make the product flow.
•
Ensure that this happens at the pull of the customer.
•
Manage toward perfection.
Both of these characterizations of lean are too abstract for the purposes of this report. MacInnes
provides a more comprehensive set of principles for manufacturing:
•
Reduce Waste:
−
Produce only to order.
−
Minimize product inventory.
25
−
•
•
1
Minimize the seven wastes:
a.
Overproduction.
b.
Waiting.
c.
Transport.
d.
Extra processing.
e.
Inventory.
f.
Motion.
g.
Defects.
Ensure Quality/Continuous Improvement:
−
Focus on the customer.
−
Apply error-proofing techniques.
−
Apply visual management and the 5S’s.1
Reduce Lead Time:
−
Through product design.
−
Through supply chains
−
In production:
a.
One-piece flow.
b.
Reduce WIP.
c.
Pull scheduling.
d.
Quick changeover.
e.
Standardization.
f.
Total productive maintenance.
This is derived from the Japanese words for five practices leading to a clean and manageable work area.
26
•
•
Reduce Total Costs:
−
Target pricing.
−
Value engineering.
Use Metrics to Ensure Improvement:
−
Financial.
−
Behavioral.
−
Core process.
3.3 Core Construction Lean Principles
Koskela (1992), Ballard, Koskela et al. (2001), Picchi (2001) and others have proposed lean
principles for construction. In addition, many other authors have interpreted individual lean
principles for construction. For example, Lane and Woodman (2000) investigated the value of
flexibility in construction processes, dos Santos, Powell et al. (2000) investigated WIP and
Lantelme and Formoso (2000) and dos Santos (1998) studied the value of process transparency.
Pull scheduling was studied by dos Santos (1999) and Tommelein (1998). The application of the
flow concept has been investigated by Ballard (1999) and Alves and Formosa (2000). The
application of metrics and benchmarking has been considered by Alarcon (1996) and Lantelme
(2000). The effects of work flow variability have been examined by Tommelein, Riley et al.
(1998) and Alarcon (1996). Finally, Ballard (1999) studied the value of reliable production
planning.
3.4 Comparison of Construction and Manufacturing
Table 3.1 uses the “principles” of the four primary authorities on lean principles (two from
manufacturing and two from construction) to compare lean manufacturing principles and lean
construction principles.
To gain an understanding of the differences in lean principle between manufacturing and
construction, the fundamental differences between manufacturing and construction had to be
investigated. Literature on these differences includes documents by Crowley (1998) and Winch
(2003). The research team compiled the following comparison list using existing literature and
information obtained from questionnaires:
•
Customer Focus:
−
Constructors do not control the entire supply chain.
−
The largest constructors control only 1 percent of the market, whereas in
manufacturing the largest manufacturers may control 20 percent or more.
27
Table 3.1: Comparison of Lean Manufacturing to Lean Construction Principles
Manufacturing
Construction
Womack
MacInnes
Koskela
Ballard1
Meet the requirements of the customer
X
X
X
X
Define value from the point of view of the
customer, not from the point of view of
individual participants
X
X
X
Principle
Customer Focus
Use flexible resources and adaptive
planning
X
Cross train crew members
X
Use target costing/value engineering
X
X
X
X
Culture/People
Provide training
X
2
Encourage employee empowerment
X
Ensure management commitment
X
Work with subcontractors and suppliers to
regularize processes and supply chains
X
2
X
X
X
Workplace Organization and Standardization
Use 5S’s
X
X
Implement poke-yoke devices
X
X
X
X
Provide visual management devices
X
X
X
X
Create defined work processes
X
X
X
Create logistic/material movement plans
X
X3
X3
Practice JIT delivery
X
X
Minimize double handling, minimize
movement
X
Balance crews, synchronize flows
X
Use kitting, remove material constraints,
reduce input variations
X
Waste Elimination
Use production planning, detailed crew
instructions
X1
X
X
X
X
X
X
X
28
Table 3.1: Comparison of Lean Manufacturing to Lean Construction Principles
(Continued)
Manufacturing
Principle
Womack
MacInnes
Construction
Koskela
Ballard1
Waste Elimination (Continued)
Implement last planner/reliable production
scheduling/short interval production
scheduling
X
Practice last responsible moment/pull
scheduling
X
Ensure predictable takt times
X
Minimize WIP; use small batch sizes
X
X
X
Reduce parts count, use standardized parts
X
X
X
X
X
X
X
X
Optimize production by pre-assembly/
prefabrication
X
Use preproduction engineering/
constructability analysis
X
Reduce difficult setup/changeovers
X
X
Use decoupling linkages, understand buffer
size/location
X
X
X
X
Reduce scrap
X
Use Total Productive Maintenance (TPM)
X
Continuous Improvement/Built-in Quality
Prepare for organizational learning/root
cause analysis, suggestion program
X
Develop and use metrics for material,
labor, equipment, WIP, quality, financial
performance, productivity and rework
X
X
X
Create defect response plan
X
Encourage employee to develop a sense of
responsibility for correcting defects
X
Use stretch targets
X
X
1
Supply chain and design management principles ignored to be consistent with research scope.
2
Implied.
3
Womack treats waste at a high level: identify Type I contributory activity waste and Type II nonvalue adding waste, perform root cause analysis and identify value stream.
29
•
•
•
−
Owners are much more involved
configuration, cost, schedule and process.
−
In construction, the responsibility for success is shared between producer
and consumer construction.
in
product
features/
Culture/People:
−
In construction, high turnover results in less opportunity for training.
−
Construction workers are craft skilled; in manufacturing, they are process
specialized.
−
There are alternate ways of doing each task; production methods are in
the hands of the workers not the manufacturing engineers.
−
Production requirements, access and schedules are governed by multiple
contracts.
Workplace Organization and Standardization:
−
Construction has a fluid organization at the project level.
−
The configuration of the production environment changes constantly; it
is more difficult to maintain visual management systems.
−
Production people move through product, rather than the product moving
through production people.
−
Construction has a more difficult supply change relationship, including
different suppliers/subcontractors in different geographic regions.
−
There are alternate ways of doing each task; production methods are in
the hands of the workers not the manufacturing engineers.
−
The typical construction project is what manufacturers would consider a
prototype; it produces a unique product.
Waste:
−
The production sequence is discretionary to a very large extent.
−
Material flow is not steady state; supply lines are different at different
project locations.
−
Construction material storage locations and amounts vary at different
points in the project.
−
Construction can change the execution time by adding or subtracting
resources.
30
•
−
Construction is resource paced, and manufacturing is typically machine
paced.
−
Construction is affected by weather.
Continuous Improvement/Built-In Quality:
−
There is high turnover/less opportunity for training.
−
The ability to develop a quality tracking program is limited.
−
Production time is measured in hours in contrast to manufacturing where
it is measured in minutes or seconds.
The primary issues common to this list are the greater degree of discretionary behavior and
increased uncertainty evident in construction. In manufacturing, production systems are defined
by and controlled by the configuration of the production line. In contrast, with construction, the
production system is defined by project managers and the individual workers. With this in mind,
the manufacturing lean principles were modified, and the subprinciples shown in Table 3.2 were
developed. Table 3.2 includes the question numbers that are relevant to each subprinciple from
the questionnaire (Appendix G) that was developed to assess lean behavior in construction.
Chapter 4 organizes these principles and subprinciples into a graphic “lean wheel” configuration.
This list of principles, although similar to conventional manufacturing principles, separates
“waste elimination” into four related principles: optimize the process of construction (by
optimizing the production process itself), optimize the production process through supply chain
management, optimize the production process through production planning and optimize the
product design through constructability reviews and pre-assembly. The increased emphasis on
planning is necessary in light of the uncertainty and process discretion prevalent in construction
production. It is from this list of “presumptive” construction lean principles that the inquiry into
lean construction could be started.
31
Table 3.2: Lean Construction Principles
Principle
Subprinciple
Question
Customer Focus
Meet the requirements of the customer
1
Define value from the viewpoint of the
customer (project)
2
Use flexible resources and adaptive planning
to respond to changing needs and
opportunities
3, 4, 5
Cross train crew members to provide
flexibility
6
Use target costing and value engineering
7
Provide training at every level
8, 9, 10
Encourage employee empowerment
11, 12
Ensure management commitment
13
Work with subcontractors and suppliers to
regularize processes and supply chains
14
Encourage workplace organization and use of
the 5S’s
15, 16
Implement error-proofing devices
17, 18
Provide visual management devices
19, 20
Create defined work processes for repetitive
tasks
21
Create logistic, material movement and
storage plans that adapt to changes in
workplace configuration
22, 23, 24
Minimize double handling and worker and
equipment movement
25, 26
Balance crews, synchronize flows
27, 28
Remove material constraints, use kitting,
reduce input variation
29
Reduce difficult setups and changeovers
30
Reduce scrap
31, 32
Use TPM
33
Culture/People
Workplace Organization/
Standardization
Waste Elimination Part I
(Process Optimization)
32
Table 3.2: Lean Construction Principles
(Continued)
Principle
Subprinciple
Question
Waste Elimination, Part II
(Supply Chain)
Institute JIT delivery, supply chain
management
34
Waste Elimination, Part III
(Production Scheduling)
Use production planning and detailed crew
instructions, predictable task times
35
Implement last planner/reliable production
scheduling/short interval production
scheduling
36
Practice last responsible moment/pull
scheduling
37
Use small batch sizes, minimize WIP
38, 39
Use decoupling linkages, understand buffer
size and location
40
Reduce parts count, use standardized parts
41
Use pre-assembly and prefabrication
42
Use preproduction engineering and
constructability analysis
43, 44
Prepare for organizational learning and root
cause analysis
45, 46
Develop and use metrics to measure
performance; use stretch targets
47, 48, 49
Create a standard response to defects
50
Encourage employees to develop a sense of
responsibility for quality
51, 52
Waste Elimination, Part IV
(Product Optimization)
Continuous Improvement
and Built-In Quality
33
4.0 Research Methodology
This chapter describes the overall plan for original data collection, data analysis and methods for
answering the research questions stated in Chapter 1.
4.1 Restatement of Research Questions
The fundamental goal of this research was to determine whether the construction industry could
benefit from the innovative approaches adopted by manufacturing during the past decade.
Specifically, the research team sought to answer the following questions:
•
construction?
•
What is nature of the typical construction production value stream?
•
What is the value stream for field production activities and for the field portion of
material delivery and handling?
•
•
•
•
4.2 Developing Lean Principles for Construction
4.2.1 Goals
The following goals were set for the research:
•
Develop a comprehensive set of lean principles for construction.
•
Validate principles by field observations of lean behavior, value stream mapping
and interviews with early lean adopters.
4.2.2 Approach
The approach used was to synthesize the available literature and original field data into a set of
lean principles for construction.
There exists a complex set of relationships between the various questions and the methods used to
answer them. Investigations began with a thorough review of the literature to establish a set of
lean manufacturing principles. Next, using the literature and interviews with lean construction
and lean manufacturing experts, a presumptive set of lean principles for construction was established. Two tasks were then performed in parallel. In accordance with the recommendations of
34
Ohno (1988), a value stream analysis was conducted to understand the nature of production value
and waste. The other task was to gain an understanding of the lean behaviors (as defined by the
presumptive set of lean principles) that are actually practiced in construction. As a basis for
defining lean construction behaviors, three sources were relied upon: evaluation of the behaviors
of the companies involved in the value stream analysis case studies, evaluation of companies who
identified themselves as attempting to apply lean principles (early adopters), and evaluation of
behaviors of early adopter companies that were reported in the literature. Finally, using the
knowledge gained by the value stream studies and the evaluation of lean behaviors, a final set of
lean principles for construction was established.
From research team observations,
recommendations were developed for actions an organization must take to become lean and
potential problems to avoid. The relationships among these various research tasks are shown on
Figure 4.1.
The following sections describe in detail the goals and methods used for analyzing the value
stream, measuring lean conformance and developing an understanding of lean behavior in
construction.
4.3 Measuring Lean Conformance
4.3.1 Goals
The following goals were set for measuring conformance to lean principles:
•
Develop a simple instrument for measuring conformance to lean principles.
•
Use this instrument for assessing adoption of lean principles in construction:
−
Assess field case study contractors.
−
Assess early adopters of lean principles.
4.3.2 Approach
The approach used included the following actions:
•
Identify lean principles for construction.
•
Develop lean conformance questionnaire.
•
−
Test, modify and redesign instrument.
−
Validate and calibrate answers from survey.
Characterize lean behaviors in construction:
−
Compare early adopters and case study contractors.
35
Figure 4.1: Overall Lean Construction Research Plan
36
As discussed in Chapters 2 and 3, there are many forms of lean principles in the literature. The
first task was to organize the presumptive set of principles in a manner that would facilitate an
evaluation of AEC organizational behavior against the principles. Additionally, the research team
interviewed several leading lean researchers and early adopters of lean principles. Finally, the
team relied on the experience and opinions of its members, many of whom had lean clients or
who were themselves adopting lean ideas.
A simple visual device, called the “lean wheel,” was developed for the manufacturing industry
(Tapping, Luyster et al. 2002). This tool was adapted for use with the presumptive set of lean
construction principles (Figure 4.2). The wheel is a device to simplify and organize lean principles into a format that is easily communicated to and understood by those new to lean theory. At
the highest level, the wheel organizes lean ideas into the following five fundamental principles:
•
Customer focus.
•
Culture/people.
•
Workplace standardization.
•
Waste elimination.
•
Continuous improvement/built-in quality.
Each of these principles was further divided into 16 subprinciples, represented graphically on
Figure 4.2.
Customer
Focus
Continuous Improvement/
Built-In Quality
Error Proofing
Optimize
Value
Flexible
Resources
Metrics
Training
Organizational
Learning
Response
To
Defects
People
Involvement
Optimize
Production
Schedule
Waste
Elimination
Organizational
Commitment
Supply
Chain
Management
.
Visual
Management
Optimize
Production
System
Workplace
Organization
Optimize
Work
Content
Defined
Work
Processes
Workplace
Standardization
Figure 4.2: The Lean Wheel (after Tapping, Luyster et al. 2002)
37
Culture/
People
One of the goals for this project was to develop a questionnaire that could be used by companies
to help them self-assess their lean behavior. The lean wheel was used as the foundation for the
questionnaire. In addition to helping companies conduct a self-assessment, the questionnaire had
a secondary purpose of helping the research team assess the lean behavior of the lean and nonlean contractors on this project.
Starting with each subprinciple, questions were developed that were relevant to construction
practices and lean theories. The questionnaires progressed through several iterations as early
drafts were administered at jobsites and company headquarters. Additionally, early versions of
the questionnaire were reviewed by lean practitioners and academics. These early trials led to
further modifications of the questions to make them clearer and more concise and to eliminate
questions that were not effectively measuring lean behavior.
The last step in the questionnaire development was to evaluate its validity. University of
Colorado academic resources helped establish the validity of the questionnaire using both
quantitative and qualitative means. Faculty from Sociology, Psychology, Marketing and Applied
Math were enlisted to improve and test the final questionnaire. Their suggestions prompted
modifications of question phraseology and the scoring scale. In addition, they directed the
research team toward the Cronbach’s alpha technique to measure questionnaire consistency.
The final step in developing the lean wheel was to use the final, validated questionnaire to guide
interviews with case study and early adopter contractors. A more detailed discussion of this
process is presented in Chapter 5.
4.4 Value Stream Mapping
A fundamental maxim of lean production systems is the need to understand the value stream of a
product. Taiichi Ohno (1988) and Shigeo Shingo (1981) spent years identifying and defining the
components of the value stream within the Toyota Production System. To this day, Toyota
continues to redefine the shape and function of its value stream. How does one define waste so
that all parties involved with the construction value stream can recognize it? It is the goal of
these field studies to help shape, define and quantify construction wastes and thereby improve the
typical construction value stream.
Waste is commonplace in typical construction projects and processes. The waste that can be
identified on the jobsite represents only a small fraction of the waste in the entire delivery
process. At every level in the typical construction organization, waste is evident. Many top
manufacturing companies reach levels of 60 to 70 percent value adding (VA) time on their shop
floors; most will claim only 5 to 10 percent contribution over their entire value stream from
development to delivery. Using lean concepts as the foundation, the nature of VA actions and
waste can be defined. Ohno (1988) subcategorizes waste into non-value adding but required
(NVAR) Type I muda, and non-value adding (NVA) Type II muda. Because of the relatively
uncontrolled and changeable nature of the construction production environment, the NVAR
actions are relatively more common than in manufacturing production. For instance, in-process
inspections (NVA-Type I muda) are typical for any process piping. The material and welds must
be checked during installation; otherwise, the safety of the workers, and possibly the future
owners of that pipe, may be compromised. While the action of inspecting the pipe does not add
value for the customer, it is an action that is required by current codes and industry standards;
therefore, it cannot be eliminated. This type of action can, however, be limited through
38
reorganization of the work processes or even through the development of an entirely new process
for installing pipe.
After definitions for VA, NVAR and NVA actions were created, the research team focused on
procedures for collecting and analyzing these data for typical construction tasks. Development of
procedures for a construction value stream analysis followed the self-imposed limits of this study.
First, the effects of design activities on lean performance were excluded. Projects can be
designed to facilitate lean performance. Project design can be delivered in such a way so as to
enable lean production. These factors were not considered in the value stream studies. The
effects of supply chain issues that are manifested away from the jobsite were also excluded, but
material supply from the time that materials entered the jobsite was included. Others (Arbulu
2002; Tommelein and Li 1999; Tommelein, Akel et al. 2003) have studied supply chain issues
and lean performance.
Another issue affecting value stream mapping is the time scale over which waste becomes
evident. Most wastes, such as worker inactivity (waiting), are immediately evident and
quantifiable by observing the value creation process of the crews. However, other wastes, such as
punch list items, are only evident to those who can observe the project over a long time. Since
data collection for this study was organized around short site visits, the data analysis was
concentrated on the wastes that were evident over a short time.
The typical value stream map must describe the entire construction process flow (Rother and
Shook 1998). Theoretically, the value stream would begin with the collection of raw material and
end when the owner (end customer) receives the finished product. This study focused on
individual construction production processes in the overall value stream. Specifically, data was
collected, analyzed and then used to create value stream maps for a typical structural steel
erection process and the installation process for large bore piping. These specific processes
represent two very different value generation mechanisms. The structural steel erection process is
an equipment intensive, highly repetitive, configuration driven process with relatively short cycle
times. In contrast, piping installation is a labor intensive, nonrepetitive process that has flexible
work sequences with long cycle times. By focusing on these different processes, it was possible
to show that the value stream mapping procedures are flexible enough to represent most construction production processes.
Ultimately, value stream maps will be used to quantify and track wastes related specifically to
material in their respective processes, as well as the production operation itself. These ideas are
further clarified and expanded in Chapter 6, where the detailed definitions for waste and the
methods used to identify and quantify waste are presented. Chapter 6 also separates the
conventional value stream map into three distinct levels. Level One is used to track wastes
associated with material and provide an overview for the work distribution values related to VA,
NVAR and NVA for an entire construction production process. Level Two tracks wastes
associated with worker and material flow as the process proceeds through the various
construction stages. Level Three dives deeper into the process and analyzes each worker’s
contribution to the various work categories.
4.5 Bringing It Together
The ultimate task was to combine the knowledge gained through interviews and the literature
search with the knowledge gained from the value stream study to define and refine an accurate set
of lean principles for construction. This was accomplished by first evaluating the applicability of
39
each of the lean principles identified in the presumptive set. Next, an evaluation was made to
determine which participant in a project should exhibit this lean behavior: the owner, constructor,
subcontractor, material supplier or designer. Finally, it was determined whether the lean principle
should be applied at the contractor’s organization level, project level or crew level.
40
5.0 Creation and Use of a Lean Assessment Instrument
5.1 Foundation/Design of the Questions
A primary goal of this research was to develop an instrument to measure a company’s
conformance to lean construction principles. The team chose to develop a questionnaire that
would accurately measure conformance to the lean principles and subprinciples and at the same
time would be concise and easy to use. The literature on questionnaires indicated that lengthy
surveys elicit casual answers. The research team relied on expertise available among colleagues
(Professors Luftig, McClelland and Boardman) in Sociology, Psychology, Marketing and Applied
Mathematics at the University of Colorado to achieve both of these goals.
The literature on questionnaire design stresses the need to verify the survey by distributing
sample versions. Oppenheim (1992) suggests that “Questionnaires have to be composed and tried
out, improved and then tried out again, often several times over, until we are certain that they can
do the job for which they are needed. This whole lengthy process of designing and trying out
questions and procedures is usually referred to as pilot work.” In accordance with this rule,
research team members repeatedly asked coworkers to complete the questionnaire and provide
comments. Additionally, early versions of the questionnaire were reviewed by contractors and
academics familiar with lean principles. The following feedback/suggestions were obtained:
•
Reword questions for clarity.
•
Ensure that the questions not lead the respondent toward a “right” answer.
•
Clarify the completion instructions.
•
Simplify the questions by using familiar vocabulary terms.
•
Number the questions.
When comments from evaluators were consistent with advice from survey design literature,
changes were made and the questionnaire was re-administered to new test groups. More details
on this test, modify and re-test procedure are provided in Section 5.5. “It is essential to pilot
every question, every question sequence, every inventory and every scale in your study. If the
pilot work suggests improved wordings, you need to pilot those, too. Take nothing for granted.
Pilot the question lay-out on the page, pilot the instructions given to the respondents, pilot the
answer categories, pilot even the question-numbering system” (Oppenheim 1992). The research
team adhered to this advice and developed the questionnaire with the utmost care. As the
research design became more definitive, the questionnaire changed accordingly. For example,
one part of the research dealt with data collection from field studies pertaining to value stream
mapping. As the lessons from the value stream mapping studies became clearer, certain aspects
of the questionnaire were emphasized or reduced. The process of design and redesign had
unanticipated positive outcomes. First, the overall questionnaire was shortened, which served to
increase the voluntary accurate response rate. Second, questions became more explicit, which
again led to more accurate responses. On the advice of the sample group, some questions were
41
reworded to make them more understandable. Oppenheim (1992) spoke in depth in his book
about the difficult task of the respondent to answer the questions accurately:
...it is difficult enough to obtain a relatively unbiased answer even from a willing
and clear-headed respondent who has correctly understood what we are after,
without making our task virtually impossible by setting off this ‘train of
responding’ on the wrong track through poor question wording.
The questionnaire was designed around pairs of statements. One half of the pair of statements
described a non-lean behavior, and the other half described a corresponding lean behavior. Since
applying lean principles leads to many effective jobsite behaviors, it was difficult to avoid
making those choices more attractive. Wording was selected that made both statements seem
favorable so that the respondent would be forced to choose the one that more accurately described
his or her company. If one statement seemed more favorable than its counterpart, then it could be
perceived as a leading question. Another suggestion that was implemented from the sample
group feedback was to add question numbers. The first draft consisted of 55 unnumbered
statements. Rea and Parker (1997) stated that “...being sensitive to questionnaire length is to
make certain that the questionnaire is not so long and cumbersome to the respondent that it
engenders reluctance to complete the survey instrument, thereby jeopardizing the response rate.”
When question numbering was added, the respondents had an idea as to the parameters of the
document, which in turn focused their attention on answering the questions rather than on the
duration of the process.
A Likert scaling system was used for the questionnaire. “A Likert scale entails a five-, seven-, or
nine-point rating scale in which the attitude of the respondent is measured on a continuum from
highly favorable to highly unfavorable, or vice versa, with an equal number of positive and
negative response possibilities and one middle or neutral category” (Rea and Parker 1997).
The Likert scale is the most popular scale in use today (Oppenheim 1992). It is simple to
understand, and it provides the evaluator more information than that provided by simple yes/no or
agree/disagree responses. A five-point Likert scale was initially used, but on the advice of faculty
colleagues (McClelland 2003), it was changed to a seven-point scale and an N/A response was
included. Figure 5.1 shows an example of a seven-point Likert scale question, in which a score of
“1” corresponds to the statement on the left and a score of “7” corresponds to the statement on the
right. Larger response ranges lead the respondents to answer more accurately and more honestly.
The project is built
precisely according
to plans
The Contractor
discusses ways to
1
2
3
4
5
6
7
N/A
modify the plans to
reduce costs while
maintaining quality.
Figure 5.1: Example of a Seven-Point Likert Scale Question
Experts in questionnaire design agree that questionnaires cannot be perfect. There will always be
some degree of uncertainty in the responses. “The function of a question in an interview schedule
or questionnaire is to elicit a particular communication. We hope that our respondents have
certain information, ideas or attitudes on the subject of our enquiry, and we want to get these
from them with a minimum of distortion” (Oppenheim 1992). In summary, the Likert scale
scoring system allowed the desired information to be acquired while at the same time keeping the
survey simple for respondents. “The Likert scale works particularly well in the context of a series
42
of questions that seek to elicit attitudinal information about one specific subject matter” (Rea and
Parker 1997). The specific subject matter was lean construction practices.
5.2 Design of the Questionnaire Using Field Studies
The survey was administered to contractor managers and employees at each of the jobsites that
were visited for the value stream case studies (six case studies in all). In the first field data
collection, the questionnaire was distributed to employees ranging from the project manager to a
crewman responsible for bolting steel girders and bar joists into place. Many of the responses to
this first questionnaire from the crew were marked N/A. It was discovered that many of the lean
behaviors that were being measured were not the responsibility of the crew members. As a result
of these first trials, the original questionnaire was split into three separate questionnaires, one for
the project management level, one for the crew level, and one for the executive or organization
level. Of the original 55 questions, there was only one question that was applicable to all three
levels. Thirty-four of the questions were applicable to two of the levels, while the remaining
20 questions were applicable to only one facet of the company. Ultimately, the organizational
questionnaire contained 26 questions, the project level questionnaire contained 50 questions and
the crew level questionnaire contained 17 questions.
While the respondents were filling out the questionnaires, the field study team was evaluating the
contractor’s lean behavior. At the end of each field data gathering phase, the study team graded
the contractor’s lean behavior using the questionnaire. The study team’s average answer was
then compared to the average response from the contractor’s personnel. Attention was focused
on those questions in which the research team’s assessment differed from the contractor
personnel’s assessment by two or more points on the Likert scale. This analysis was repeated so
that questions that had confusing wording or leading answers could be identified. This process
was a principal tool for improving the questionnaire.
The research team distributed and administered the questionnaires in person and was able to
achieve a 100 percent response rate. A response rate of 50 to 60 percent is considered
satisfactory when administering a questionnaire (Rea and Parker 1997). The ability to achieve
full participant response made the task of analyzing the questionnaires much easier. It was not
necessary to establish the type of people that filled out the survey; the participants worked in the
construction industry. This was the anticipated population at which the survey was directed. It
was very beneficial to the team to visit each of the case study jobsites. Each trip presented an
opportunity to explain the questionnaire, its current use and its end goal to a wide variety of
participants.
Ultimately, the questionnaire was distributed to the focus group. The focus group consisted of
the employees working at the jobsites that were visited for data collection. The research team
visited six jobsites, value stream data was collected at all six sites, and the questionnaire was
distributed at five of the jobsites. The sites were located in various parts of the United States:
•
Richmond, Virginia--Steel Erection.
•
Kirtland, New Mexico--Process Pipe.
•
Michigan City, Indiana--Process Pipe.
•
Birmingham, Alabama--Steel Erection.
43
•
Birmingham, Alabama--Process Pipe.
•
Smyrna, Delaware--Steel Erection.
At each site, the questionnaire was distributed to approximately 10 employees of the onsite
contractor. On average, four crew members, four project management level employees and two
executives filled out the questionnaire. Each work level received a different questionnaire that
contained only questions relevant to their job.
5.3 Case Study Interviews
To further scrutinize lean principles, a parallel study to the questionnaire using oral interviewing
techniques was conceived to capture the lean behaviors and opinions of contractors and owners.
The questionnaire was used as a structured interview guide. The oral interview techniques
provided explanations of lean practices, as opposed to a simple numerical response. These
explanations and insights helped simplify the questionnaire and shift emphasis to specific
principles. At a minimum, the contact person from the research team was interviewed for each
jobsite. Since they had a better grasp of lean principles than their peers, administering the
interview was straightforward. Each of the subprinciples was defined for the interview
participant, and they were then asked to state which practices they used followed that lean
subprinciple. At several of the case study sites, field management personnel also participated in
oral interviews. The purpose of the interviews and questionnaire was to understand which lean
principles were actually used in construction. In other words, if a company was using a lean
principle and it was effective, then it may be concluded that the principle may be translated from
its manufacturing base to the construction industry. The more difficult task was determining
whether non-use of a principle indicated unfamiliarity with the concept or inapplicability of the
principle in construction. Often, an employee of one of the interviewees would relate plans for
implementing or trying a certain lean practice in the near future. It was felt that when the
company had a better grasp of lean construction as a whole, the implementation of more
innovative ideas would be easier to introduce. This relates to an important concept: the role
culture plays in the success of lean principles. Employees have an easier time supporting a
practice if it is not completely foreign to them. Changing a company’s culture in a short period of
time is a difficult task. The interview process produced results in all subprinciples that could not
have been achieved solely through the questionnaire. The questionnaire provided a broad
understanding of each company, while the interviews provided greater depth.
Companies that professed to be early adopters of lean principles were also interviewed. These
early adopters shared their insights and helped the research team understand their approaches for
implementing lean in construction.
5.4 Early Adopter Interviews
The goal of interviewing early adopters was to gain a better picture of which lean principles were
practiced in the field when a company was trying to implement lean practices on its projects. The
people interviewed understood lean from the manufacturing point of view, often using the
Japanese word or phrase for a subprinciple that was discussed. Most had a clear understanding of
the existing work in lean construction. The one common theme from each early adopter was their
belief that lean theory is helpful; however, the focus of each early adopter’s lean implementation
was highly variable. Some focused on field production, others on developing a lean culture and
others on supply chain issues. The early adopters were very clear about their intentions to use
44
lean, as opposed to the others interviewed who were more skeptical about implementing lean
theories. This was evidenced by the fact that early adopters had schedules for implementation of
certain lean practices. Some lean practices were being held for a smaller project so they could be
tested prior to full company implementation. Other lean behaviors were being implemented right
after a previous one was fully absorbed. The difference between the early adopters and the case
study participant companies was the adherence to a schedule for lean implementation.
The results and conclusions from both the early adopters’ interviews and the case study
participant interviews are discussed later in this chapter.
5.5 Validation of the Questionnaire
The validation of the questionnaire progressed through three stages. The first stage was the pilot
work. This included the creation of the questionnaire using the lean principles and the
distribution of the questionnaire to the sample groups. After the pilot stage, the questionnaire was
administered to employees of the jobsites that were visited by the research team. In this second
stage, the validation work came from deciphering the participants’ responses. The third and final
stage in the validation process was the statistical analysis of all the responses. The statistical
analysis led to conclusions about whether the questionnaire was reliable as a self-assessment tool
in lean construction.
5.5.1 Stage One: Pilot Work
The pilot work was vital in bringing the questionnaire up to standards. This stage did not actually
validate the tool, but was a method for fine-tuning the questionnaire. The sample group
respondents offered suggestions that were utilized in the final design of the questionnaire.
The pilot work was necessary for eventually administering a simple, understandable questionnaire
to the focus group. The participants in the pilot stage were all construction professionals, and if
they were unfamiliar with some terminology used, the questionnaire had to be changed. The
main goal of the pilot work was the development of a comprehensible and clear tool. Eventually,
the questionnaire will be used as the basis for a lean self-assessment tool; therefore, it was
developed to be as easy as possible to administer and understand. The process of improving the
questionnaire continued until there were no more remarks regarding instructions or terminology
definitions.
5.5.2 Stage Two: Focus Group Responses
After the pilot work was complete, the questionnaires were administered to the focus group. The
focus group consisted of employees from each jobsite visited. The questionnaire pertaining to
employees on the crew level was distributed to the field labor, while the questionnaire relevant to
project management was distributed to employees located onsite. The questionnaire pertaining to
the executive level was mailed to the organizational employees working at headquarters. While
in the field, a technique called “debriefing” was used. Fowler (1995) explains that “the most
universal strategy for evaluating self-administered questionnaires is to have respondents complete
them, then carry out a brief interview with the respondents about the survey instrument. In
addition, respondents can be asked about any problems they had with reading and answering
questions.”
45
Evaluation of the accuracy of the participants’ responses was accomplished by measuring them
against an agreed upon standard. The consistent standard used was the research team’s
assessment. Members of the research team who were present at each case study visit completed a
questionnaire based on their personal observation of the activities and practices at the jobsite.
The comparison between the research team’s average answer for each question and the answer
given by the respondents was used to validate the questionnaire. As stated before, if there was an
average discrepancy larger than two on the Likert scale between research team answers and the
respondent’s answer, the question wording and content were further analyzed. Of the 55 original
questions, eight questions were eliminated as a result of this process. Other questions that were
borderline in terms of validity were reworded and retested for adherence to this standard.
It was important to understand how the research team’s unbiased assessment of jobsite lean
performance compared to the contractor’s staff assessment. Differences between the two
assessments could be caused by a poorly worded question or by bias on the part of the contractor
personnel. Some degree of bias from the project management staff and the craft workers was to
be expected. Results were analyzed for a limited degree of bias and a consistent trend in the bias.
That is, if a question exhibited contractor responses that were consistently higher (better) than the
research team responses, the difference was attributed to bias, pride in workmanship, etc. On the
other hand, if the contractor responses showed a large differential, or if the differential was
sometimes higher and sometimes lower than the research team, the difference was attributed to a
misunderstood question. Using this process, questions were improved, reworded and, in some
cases, eliminated from the questionnaire.
Interestingly, the resultant scores from the organization level were the most consistent with those
of the research team observers. The project management level was also very consistent with
those of the research team. The crew level, on the other hand, had the largest discrepancy from
the observers. At the organization level, the average differential between a respondent and the
research team was 1.4 points. At the project management level, the difference was 1.5 points. At
the crew level, the difference was 2.3 points. These results were consistent across all jobs. The
crew level always had the highest discrepancy, while the other two levels were lower and within
decimal points of each other. Since the discrepancies were consistent between company levels
and between jobsites, the final validation test was to statistically analyze the response results for
reliability.
5.5.3 Stage Three: Statistical Reliability Analysis
The final step in validating the questionnaire was through statistical reliability testing.
Cronbach’s alpha coefficient was used to measure the reliability of the questionnaire.
“Cronbach’s alpha is an index of reliability associated with the variation accounted for by the true
score of the ‘underlying construct.’ The construct is the hypothetical variable that is being
measured” (Hatcher 1994). Cronbach’s alpha can be written as a function of the number of test
items and the average inter-correlation among the items. The formula for the standardized
Cronbach’s alpha is as follows:
α=
N*r
1 + ( N − 1) * r
46
Where:
N is the number of items, and
r is the average inter-item correlation among the items.
Cronbach’s alpha is a coefficient from 0 to 1 that measures the consistency and correlation
between responses to a set of similar questions. For this report, the construct measured was the
correlation between the responses for the questions pertaining to certain lean construction
principles. This reliability coefficient test was recommended by several researchers at the
University of Colorado (McClelland, Luftig, Boardman) and by other experts. “You may
compute Cronbach Coefficient Alpha, Kuder Richardson (KR) Formula, or Split-half Reliability
Coefficient to check for the internal consistency within a single test. Cronbach Alpha is
recommended over the other two.” (Yu 1997) “When items are used to form a scale, they need to
have internal consistency. The items should all measure the same thing, so they should be
correlated with one another. A useful coefficient for assessing internal consistency is Cronbach’s
alpha” (Cronbach 1951).
In this questionnaire, questions were developed around each of the five main principles.
Cronbach’s alpha test demonstrated whether the grouped questions were consistent in measuring
the same lean construction principle. Five tests were conducted wherein each of the five main
principles was treated as the single construct. The results of each test were taken to see if the
questions asked were consistent in focusing on that one principle. Since alpha is a coefficient, its
range of values is from 0 to 1 and, therefore, each result was given as a decimal. “There isn’t a
generally agreed cut-off. Usually 0.7 and above is acceptable” (Nunnally 1978). The goal of the
research team was to produce an alpha score of at least 0.7 for all five tested principles.
To perform the statistical tests, SPSS/PC+, a powerful software package for microcomputer data
management and analysis, was used. Questionnaire results were entered into the software
database as an Excel spreadsheet, and then the Cronbach’s alpha coefficient was completed for
the designated questions. The SPSS results for each of the five tests are shown in Table 5.1.
The results of the Cronbach’s alpha tests were positive. All five principles had coefficients of at
least 0.76 and up to 0.95. As a result, it was concluded that this questionnaire was valid and
reliable tool for its purpose of measuring conformance to lean principles. The final questionnaire
can be found in Appendix G.
5.6 Use of Lean Principles in Construction
The following subsections summarize the important findings about the use of lean principles in
construction. These results were derived from analysis of the questionnaires administered at the
five value stream case study sites. Each section examines application of one lean principle at
each of the three study levels: crew, project management and executive or organization level.
5.6.1 Customer Focus
The responses from the completed questionnaires indicated that communication with the client
was not as central to the construction process as lean theory would suggest. Contractors were
unclear about who the owner (client) actually was. Value added processes were not always
defined by the owner’s needs or in terms of the project as a whole. There is still work to be done
in terms of understanding the customers’ requirements and being flexible in meeting their needs.
47
Table 5.1: Cronbach’s Alpha Results
Principle
Cronbach’s Alpha Coefficient
Customer Focus
0.7467
Culture/People
0.8564
Workplace Standardization
0.8642
Waste Elimination
0.9548
Continuous Improvement/Built-In Quality
0.9039
R E L I A B I L I T Y A N A L Y S I S - S C A L E (A L P H A)
Reliability Coefficients
N of Cases = 24.0
Alpha = 0.7467
N of Items = 7
N of Cases = 41.0
Alpha = 0.8564
N of Items = 7
N of Cases = 41.0
Alpha = 0.8642
N of Items = 10
N of Cases = 41.0
Alpha = 0.9548
N of Items = 18
N of Cases = 41.0
Alpha = 0.9039
N of Items = 8
48
5.6.2 Culture/People
Training was prevalent in the industry, but not to the extent that companies were taking the time
to teach their employees about lean practices. For the most part, training occurred on company
time, and training on matters outside of specific job responsibilities was not common practice.
However, companies were trying to empower their employees to share their improvement ideas.
This was a lean practice that even non-lean companies supported. There was an overall sense of
the need for improvement in the industry by people at the organization level.
5.6.3 Workplace Standardization
Companies encouraged their employees to be clean and organized on the jobsite. These
recommendations, however, were not always followed. There was a need for the project
management level to increase its use of visual aids to encourage the workflow and cleanliness of
the jobsite. It was generally agreed that visual aids would help, but the implementation of this
practice was still in its inception for many of the focus group companies. The documentation of
work processes and a defined logistics plan were inconsistently used within the focus group.
5.6.4 Waste Elimination
The focus group lacked consistency concerning balancing crew sizes, crew sequencing and
minimizing movement by people, materials and equipment. For the most part, respondents
answered that there was room for improvement in this regard. The question and/or subprinciple
that garnered the most negative responses dealt with the optimization of design with field
installation. Most respondents answered that certain design aspects of their project made
construction more difficult than necessary.
The consensus from the completed questionnaires was that JIT delivery of supplies was still in its
adolescent stage. Some contractors were trying to use this method with large suppliers, but they
would generally feel more comfortable with the needed materials stored in a lay-down area. In
terms of completing work products for the next crew to use, respondents were evenly divided
between making them available in small batches or in large batches of the finished products.
Unlike the lean manufacturing industry, these respondents answered that they try to start a work
activity as soon as possible rather than waiting until the last responsible moment that still
supports the schedule.
5.6.5 Continuous Improvement/Built-In Quality
One tool that almost all lean construction companies used was a lessons learned file. The
questionnaire results showed that companies that were the least lean also did the least in terms of
lessons learned. The companies that were in the beginning stages of becoming lean tried to
incorporate some sort of lessons learned file into their corporate knowledge base. There was a
split between the focus group as to which companies made a consistent effort to monitor their
work using established metrics. These measurements consisted of productivity reports, quality
assurance reports and sometimes cost reports. In terms of error-proofing, there was still a need to
conduct more constructability reviews before the design was complete. Most of the contractors
made it a point to place some sort of directional marking on their supplies to ease the job of the
installer. Lastly, the focus group was not consistent regarding having a plan in place to deal with
defects.
49
5.7 Case Study Interview Results1
These interviews were conducted primarily by members of the research team with representatives
of the companies working on the value stream case study jobsites. Of those interviewed, only one
of the companies used lean practices on its project. The interviews were valuable in gathering
information that could not have been collected through the questionnaires. All the participants
were eager to describe current practices on their jobsites. The face-to-face interviews provided
deeper understanding of current lean (and non-lean) practices on typical construction jobsites.
The following subsections summarize the results of these interviews according to each of the
major lean principles.
The interviews did not indicate that an intense focus on customer value was common in
construction. Understanding the customer’s requirements is a focal point of lean theory in
construction and manufacturing. The only practice commonly noted by the participants was the
use of formal design review sessions with the owner during the preconstruction phase of their
jobs.
An important aspect of lean behavior is creating a culture wherein employees are confident about
the process and strive for continual improvement. Employee empowerment and the commitment
of the organization to improve its processes are essential for creating a lean culture. Training
sessions are necessary to educate employees about lean principles. All of the participating
companies trained their employees in construction practices, but only one of the companies
focused training sessions on lean behavior. The participants stated that their company
encouraged employees to provide feedback on improvement. This company created a tool called
the Lean Daily Management System which fostered a process of feedback participation. The
participants stated that more people had become involved and empowered because of this tool.
All the companies stated that they were looking for ways to improve their processes.
Workplace organization is a significant part of this principle. Each company works to maintain a
clean and organized workplace, since this invariably increases safety standards. However, no
specific lean practices such as the 5S’s were used by any of the participant companies. Visual
management is an important lean behavior on a manufacturing floor. There was some use of
visual aids regarding schedule, safety and, occasionally, productivity. For the most part, visual
devices were posted in the project management trailers, but not at the worksite as one would
expect for proper lean implementation. The defined work processes used by each company were
typically in the form of site logistics. One company had a lessons learned file for work tasks.
1
Interview notes for the case study contractors can be found in Appendix H.
50
This principle was not actively employed by the participant companies. The desire to improve
practices was often cited as a goal; however, most work tasks were organized and planned by
individual work crews. None of contractors used staff to support the planning of individual work
operations. One company stated that a great deal of planning went into minimizing the
movement of its employees between and during work activities. All the participant companies
mentioned the lack of communication between the design team and the field installation team.
One of the companies used a modified version of the “last planner” technique. Another company
made an effort to pass along products in small batches or continuous streams. None of the
companies set their schedule to the last responsible moment that still supported the schedule; they
all believed that was too risky. JIT delivery is still only a vision for most of the companies;
however, some companies made efforts to deliver in smaller batches to eliminate excessive
handling.
Most companies had a lessons learned file on their internal intranet. Effectiveness of lessons
learned appeared to be linked to similarities between a company’s projects. Companies with
many dissimilar jobs did not utilize lessons learned as often as those with jobs that were similar in
nature. All of the companies stated that they measured quality on all their projects. Only two of
the participant companies measured productivity on each job. Regarding error-proofing, the
companies specializing in steel erection were more prone to use poke-yoke (error-proofing)
devices to ensure a one-way only fit and no erection mistakes. Finally, two of the participant
companies had a response plan in place in case a defect occurred. The plan essentially consisted
of “stopping the line” and making a decision about the path forward.
In general, it appeared that case study contractors adhered to industry best practices. With a few
exceptions, most of the contractor personnel were unaware of lean manufacturing principles.
5.8 Early Adopter Interview Results1
Early adopters were contractors who were aware of lean principles and were actively trying lean
techniques on their projects. Each of the three early adopter companies interviewed employed
lean practices in their everyday functions. Lean construction is a relatively new concept, and
these early adopters are still learning and expanding their lean functions.
There were numerous practices incorporated by these companies to try to meet customer
requirements. Target costing and value engineering were used to show clients alternate scenarios.
One company encouraged a design-build or design-assist delivery system that forced
communication between the contractor and designer to give the customer the most value. Some
will argue that these are simply best practices in construction; however, all three companies were
steadfast in their belief that constant communication between the client and contractor was
essential in bringing the client the most value. Each of the early adopters used some form of
1
Notes from the interviews with the early adopter contractors can be found in Appendix H.
51
short-term planning to be proactive, rather than reactive, with any new project development. This
type of planning creates flexibility because of the increased communication between all involved
parties.
A clear difference between the early adopters and the case-study companies was the outlook on
creating a lean culture. The early adopters made it a point to push lean thinking throughout their
companies; each had mandatory training sessions based solely on lean behavior. These sessions
ranged from eight-hour sessions to mandated courses that educated on three different levels of
lean theory. The early adopters took training very seriously and spent a considerable amount of
time and money to ensure that their employees were properly trained. The three companies used
different practices to empower their employees, although they all had the same underlying
motive: to create an environment in which employees are always looking for ways to improve.
These practices ranged from the creation of award programs for implemented suggestions to the
mandate that employees provide feedback in the form of opportunities for improvement (OFIs).
These practices encouraged employees to participate in the continual improvement of company
processes. Finally, organizational commitment was obvious for each of the early adopter
companies.
Workplace organization varied a great deal in the early adopter companies. One company was
steadfast in its implementation of the 5S tool (sort, straighten, sweep, standardize and
systematize); while another company said that it was working on implementing 5S in the future.
They all strove for clean and organized jobsites. One company created a box for each crewman
that contained everything he or she would need for the upcoming day. Another difference
between the early adopter companies and the case-study contractors was the use of visual
management. These companies used visual aids to a much greater degree than the other
contractors. It was seen on the actual worksite and in the distribution of project information.
Visual aids representing workflow and site logistics were more available on the early adopter’s
jobsites. One of the companies went to great lengths to produce visual tools that helped
employees plan, communicate and coordinate their activities. They also created numerous
checklists that gave their employees a better picture of what was required for each activity or
overall project. Each of these companies distributed visual aids that tracked productivity, safety,
short-term schedules and material handling requirements. The defined work processes of each
company were communicated through the use of the visual tools.
The lean tools used by these early adopters consisted of last planner meetings or four-week lookahead schedules that helped balance and track crew flow. Checklists were used by one of the
contractors to see if the current project was similar to a previous project; this information could
then be used to see how that project was planned. Regarding optimizing work content, one of the
companies provided its architects/engineers with JIT training to improve design coordination and
planning. Two of the companies requested that the design be conceived with more standardized
materials to make installation in the field easier. Prefabrication was another alternative
considered to ensure smooth field installation.
52
Surprisingly, supply chain management was not widely used by the early adopter contractors.
They spoke of JIT delivery, but stated that it was not in prevalent use in their companies. There
were too many possibilities in the current environment for supplies or materials to be delivered
late, which could affect the critical path. Obviously, this is a risk that these companies are not
willing to accept at the present time. However, these companies are focused on the handoff of
finished products between subcontractors and crews. The objective is to hand off the finished
product in a continuous stream or in small batches. This is a lean behavior that is supported by
using the four-week look-ahead tool or the Last Planner System approach.
Similar to the case-study contractors, each of the early adopter companies maintained lessons
learned files. These files included OFIs or Continuous Improvement Messages (CIMs),
depending on the nomenclature used by the company. One of the companies went so far as to
have a separate lessons learned file solely for lean practices. Each of these companies monitored
quality and productivity. One of the companies even measured the amount of unused supplies
and materials on each jobsite as a way of reducing scrap. Another company decentralized its
quality control down to the lowest level of the organization. This practice goes along with the
theory that each worker should check his or her work and ensure its quality before passing the
work down the line. Surprisingly, little emphasis was placed on error-proofing by any of the
early adopters; however, each company encouraged field empowerment so that the affected
employee would raise the flag and act on a defect.
5.9 Survey of Lean Implementation in Construction Literature
Investigation of current applications of lean construction included a survey of the literature. The
following subsections detail lean applications that have been reported in the literature. These
applications are organized according to the process level, project level and organization level.
5.9.1 Lean Implementation Case Studies at the Process Level
5.9.1.1 The Oscar J. Boldt Construction Company (Tsao 2000). This case
study examined the following lean principles, methods and/or tools:
•
Work structuring.
•
Implementation of “5-Whys” to determine root causes of problems/errors.
•
Value stream mapping.
This case study focused on the construction of the Redgranite Correctional Institution in
Wisconsin. This project consisted of two housing buildings that covered a total of
140,000 square feet. These buildings were two stories tall, and their walls were made from
precast concrete panels. The first-level floors were slab-on-grade, while the second-level floors
were precast concrete slabs. The Oscar J. Boldt Construction Company was the construction
manager, and Venture was the project architect. The state awarded Boldt this design-build
project based upon a guaranteed maximum price bid of $48 million.
To illustrate current practices and the opportunities provided by work structuring, this case study
discussed the installation of 510 hollow metal doorframes at the prison project. Because the
53
project was a correctional facility, the doorframe installation process involved a special grouting
procedure, which made the installation process less routine. Those personnel involved
recognized the difficulty of the situation, but better solutions were impeded by the demands of the
installation process. This case study thus provided the opportunity to illustrate how one may
come up with alternative ways to perform the work when not constrained by contractual
agreements and trade boundaries. In addition, the importance of dimensional tolerances in
construction and how these affected the handoff of work chunks from one production unit to the
next were discussed.
5.9.1.2 JIT Practices in Ready-Mix Concrete Delivery (Tommelein and Li
1999a). This case study examined the following lean principles, methods and/or tools:
•
JIT practices within ready-mix batching and delivery.
•
Ready-mix concrete is a prototypical example of a JIT production system in construction.
Practices regarding ready-mix batching and delivery were described in this paper and depicted
using value stream mapping symbols. Each case highlighted the presence of buffers of
information, materials and time, as well as production order and withdrawal mechanisms
positioned at strategic locations to meet specific system requirements, as defined by the nature of
the contractor’s work. In this paper, the batching and delivery of ready-mix concrete were used
to illustrate a pull system. Ready-mix concrete is a prototypical example of a batch process,
where a customer process (the contractor) releases an order to batch to the supplying process (the
batch plant) and receives product as a result. This batch process does not allow any inventory of
product to be maintained, because the product is perishable.
While these practices clearly exemplify JIT production, the paper was limited in scope. No data
was included to characterize the actual performance in terms of timeliness, buffer sizes, error
rates, etc. Moreover, the paper focused on batching and delivery, which are only parts of the
entire concrete production system. Current practices for managing the concrete supply chain
upstream in terms of raw materials acquisition or prerequisite work onsite are not geared toward
JIT production.
Further investigation is therefore warranted, and significant process
improvements may be achieved by those working toward fully implementing a lean construction
system.
5.9.1.3 JIT Practices in Steel Fabrication and Erection (Tommelein 1996b).
This case study examined the following lean principles, methods and/or tools:
•
JIT practices within steel fabrication and delivery.
•
Buffer location analysis.
•
The erection of a building’s structural steel frame is a major construction phase on many projects.
The main resource in this process, the steel erector’s crane, defines not only the pace of steel
erection, but also the pace for handling and installing many other structural and non-structural
materials. This production system cannot afford any delays. Some claim that structural steel is
therefore managed as a JIT process with materials being delivered to the site as needed and
installed promptly. This is the case only in appearance, as is clear when one considers the JIT
54
principles that were developed as part of Toyota’s lean production philosophy. To illustrate the
point, this paper drew on examples of typical structural steel supply chains from the industrial and
building construction sectors. The use of symbols from manufacturing was investigated to map
key production steps, as well as buffers in between them, to elucidate where resources do and do
not flow. Industry practices in these two construction sectors vary significantly. Neither one is
lean. This paper reported on a preliminary investigation into the location of buffers in the
structural steel supply and construction process. The reasons for having buffers at various
locations were explored. A more in-depth investigation is recommended to gain a deeper
understanding of the buffer sizing criteria and steel component sequencing rules that govern
current practices. Insight into these will then help determine which buffers can be trimmed to
reduce WIP cycle times. This will support the effort of achieving “more JIT” by making
processes within individual companies, as well as across the entire steel supply chain, leaner.
5.9.2 Lean Implementation Case Studies at the Project Level
5.9.2.1 PARC Project (Ballard, Casten et al. 1997). This case study examined the
following lean principles, methods and/or tools:
•
Increased production planning.
•
Work method design.
•
Decrease variability-increase reliability.
•
Continuous improvement.
•
Increased project coordination.
The PARC project was a refinery expansion costing approximately $2.1 billion. In 1994,
consultants Mike Casten, Greg Howell and Glenn Ballard initiated a productivity improvement
program at the PARC project following an initial site visit and diagnosis. The program duration
was from November 1994 until August 1995. Before the program was implemented, the project
suffered from poor labor productivity. As a result, the current direct labor force of 10,000 needed
to be increased to approximately 18,000. This increase in labor force, however, was not an option
because of a lack of skilled workers and the inability of the project to accelerate the supply of
work. As a result, this particular improvement program focused on production planning, since it
was determined that the current planning methods were insufficient to complete the job. The
current project management model needed to be changed from a contract management model to a
production management model, which would be oriented toward the way work is done. The
following three factors were determined as key areas for project improvement:
•
How well the project is supplying the basic elements of work to the crews. These
elements include information, materials, tools, equipment, etc.
•
The method used by the crew to perform the work.
•
How well the accomplishment of the work itself meets the needs of the workers.
55
It was determined that planning reliability was important to improved project performance. To
increase planning reliability, the team of consultants introduced the subcontractors to the Last
Planner System, a system developed to improve production planning, which includes the
following:
•
Using six-week look-ahead schedules.
•
Screening processes for creating workable assignments.
•
Sizing assignments to crew capacity.
•
Charting and acting on reasons for not doing planned work.
•
Using percentage of planned weekly assignments completed (PPC charts).
Subcontractors were also introduced to first fun studies (FRS), which entailed detailed planning,
study and improvement of field operations. The results from these changes were improved
quality of subcontractor production planning as well as improvements in field operations. The
improvement program resulted in substantial increases in productivity as well as a project
completed on schedule.
This particular case study implemented production planning to increase the reliability of the
subcontractors’ work plans by allowing them to better match labor to their work and identify
reasons why work was not completed.
5.9.2.2
Linbeck Construction (Pappas 1990).
This case study examined the
following lean principles, methods and/or tools:
•
•
Decreased variability-increased reliability.
•
Linbeck Construction used the Last Planner System of production control on a remodel of the
chemistry building at Rice University. The project was a complete demo-to-structure renovation
of a university chemistry building originally built in 1925. The general contractor studied was a
merit shop contractor who specializes in commercial and building construction. Approximately
90 percent of the work on this project was subcontracted; both union and merit shop
subcontractors were involved. The construction contract was $22 million. The entire project,
including assessment and design, was $28.5 million. The construction duration was 12 months.
The contractor was responsible for all material procurement, including laboratory equipment.
The owner procured the furniture. Project staffing included one project manager, two project
engineers, one superintendent, one assistant superintendent, 15 foremen (nine from
subcontractors), and 78 craftsmen (65 from subcontractors). The construction contract was a
negotiated, cost plus fixed fee/guaranteed maximum price contract with graded incentive
bonuses. The five major subcontractors were also under the same contract arrangement. The
incentive bonuses were based primarily on the cost performance of the project.
56
Lean construction methods were fully embraced by the owner, general contractor and all major
subcontractors. There was obviously a great deal of coordination and communication;
contractors worked together, instead of at each other’s expense. This level of commitment was
critical to the success of the project. The designer was willing to implement lean construction as
long as it provided some benefit, but did not fully embrace the program. This had detrimental
effects on the timely completion of the design documents, which negatively affected the start of
the construction schedule. To mitigate some of these delays, the construction permits were
obtained individually for each floor as parts of the design were completed.
The renovation of a 70-year-old building is a challenging task. Add to this the fact that the work
was 90 percent subcontracted, and the project appeared to be a prime candidate for major
coordination problems. The lean construction approach clearly had a positive impact on the
project. Foreman delay survey data showed that delays due to common problems with tools,
information and materials were a fraction of what is experienced on most projects. This indicates
that the planning process was very effective for improving field productivity. The increased
planning, communication and coordination among project participants allowed the work to
progress smoothly, without major conflicts between contractors. This degree of cooperation
indicated that the project team accepted the concept of optimizing the project as a whole, as
opposed to optimizing individual activities or optimizing the work of individual companies.
5.9.3 Lean Implementation Case Studies at the Organization Level
5.9.3.1 Pacific Contracting (Eagan 1998). This case study examined the following
lean principles, methods and/or tools:
•
Three-dimensional design system, resulting in increased constructability and
increased reliability of information.
•
Construction method planning.
•
Employee motivation.
•
Pacific Contracting of San Francisco, a specialist cladding and roofing contractor, has used the
principles of lean thinking to increase its annual turnover by 20 percent in 18 months with the
same number of staff. The key to this success was improving the design and procurement
processes to facilitate construction onsite and investing in the front end of projects to reduce costs
and construction times. The company identified two major problems to achieving flow in the
entire construction process: inefficient supply of materials that prevented site operations from
flowing smoothly and poor design information from the prime contractor that frequently resulted
in a large amount of redesign work.
To tackle these problems, Pacific Contracting combined the more efficient use of technology with
tools for improving planning of construction processes. A computerized 3D design system was
used to provide a better, faster method of redesign that led to better construction information.
The design system provided a range of benefits, including isometric drawings of components and
interfaces, fit coordination, planning of construction methods, motivation of work crews through
visualization, first run tests of construction sequences and virtual walk-throughs of the product.
A process-planning tool known as Last Planner, developed by Glen Ballard of the Lean
57
Construction Institute, was used to improve the flow of work onsite by reducing constraints such
as lack of materials or labor.
5.9.3.2 The Neenan Company (Eagan 1998). This case study examined the following
lean principles, methods and/or tools:
•
•
•
Multi-functional teams.
The Neenan Company, a design-build company, is one of the most successful and fastest growing
construction companies in Colorado. It has worked to understand the principles of lean thinking
and looked for applications to its business using “Study Action Teams” of employees to rethink
the way they work. Neenan has reduced project times and costs by up to 30 percent through
developments such as the following:
•
Improving the flow of work onsite by defining units of production and using
tools such as visual control of processes.
•
Using dedicated design teams working exclusively on one design from beginning
to end and developing a tool known as “Schematic Design in a Day” to
dramatically speed up the design process.
•
Innovating in design and assembly; for example, through the use of prefabricated
brick infill panels manufactured offsite and preassembled atrium roofs lifted into
place.
•
Supporting subcontractors in developing tools for improving processes.
5.9.3.3 Argent (Eagan 1998). This case study examined the following lean principles,
methods and/or tools:
•
Strategic partnering.
Argent, a major commercial developer, has used partnering arrangements to reduce the capital
cost of its offices by 33 percent and total project time in some instances by 50 percent since 1991.
It partners with three contractors and a limited number of specialist subcontractors, consultants
and designers.
5.9.3.4
Neil Muller (Eagan 1998).
This case study examined the following lean
principles, methods and/or tools:
•
TQM.
Neil Muller Construction, South Africa, has used TQM techniques to achieve an 18 percent
increase in output per employee in a year, a 65 percent reduction in absenteeism in four years and
a 12 percent savings on construction time on a major project.
58
6.0 Evaluating a Construction Value Stream
6.1 Construction’s Production Value Stream
To understand where value is added in a production process, one must first learn the steps or
phases a product goes through to reach a finished state. The developers of the Toyota Production
System (Ohno 1988; Shingo 1989) and other early adopters of lean principles have emphasized
the importance of mapping out the entire production process. Mapping out all of the steps of a
production process allows one to focus on eliminating steps that are not required. Relating this to
the construction industry, value stream mapping allows each party involved in the construction
process to understand where value is generated. Tapping, Luyster et al. (2002) define a value
stream as “everything - including non-value adding activities - that makes the transformation
possible.” For construction, a transformation is the process of converting raw materials and labor
into a finished product (building, bridge, road, etc.). In other words, the value stream represents
the channels that material, equipment and workers move through to produce the finished product.
Fundamentally, value stream mapping allows one to differentiate between value adding (VA),
non-value adding but required (NVAR) (Type I muda), and pure non-value adding (NVA) actions
(Type II muda) in a construction process. To highlight areas of waste, work must be defined as
VA, NVAR or NVA. Section 6.2 defines each of these categories of work relative to the
processes of the construction industry.
6.2 Categories of Work
In general terms, inefficiencies are classified as one of three types: inefficiency due to waste
(NVA activities), inefficiency due to work that does not directly contribute value (NVAR
activities) and inefficiency due to poorly designed work processes (ineffective VA activities).
6.2.1 VA Definition
For this research, the team adopted Walbridge-Aldinger’s strict definition for VA activities as
“…any activity that changes the shape, form, or function of materials or information to meet
customer’s needs” (Walbridge-Aldinger 2000).
This definition excludes common construction work such as material handling, inspection or
temporary structures. Another less precise way of thinking about VA activities is that they are
those activities that the client is actually interested in purchasing. For example, one could say
that the client is interested in purchasing a steam line for a power plant, but not the temporary
support or testing activities that are needed to produce a finished pipeline. A VA action in this
process is the physical welding of the pipe spools into their final position. This strict definition
for VA activities has been adopted in this report to provide pinpoint focus on the customer value
equation.
6.2.2 NVAR Definition
This category can be separated into three subcategories that are required for construction
operations, yet have no permanent effect on the finished product. These subcategories include
material positioning, in-process inspection, and temporary work and support activities (TWSA).
59
6.2.2.1 Material Positioning. This subcategory includes all activities that involve the
movement of a structural steel member or pipe spool into its final position. For example, flying a
column into its final position in the structure is a required action, but it does not actually change
the physical characteristic of the finished product. The structure is physically changed only when
bolts are tightened around the baseplate. (Note: one must be careful when labeling an activity as
material positioning. Material positioning does not include moving a steel member from the laydown yard to a staging area. This action should be labeled as “transport,” which is an NVA
activity.)
6.2.2.2 In-Process Inspections. This subcategory includes actions such as the leveling,
plumbing and/or final field measurements of installed material. It also includes in-process or
production weld inspections that are required in accordance with individual project specifications.
This subcategory accounts for current construction requirements of inspecting ongoing and
finished products to ensure quality to the customer. For example, continually plumbing and
leveling the structure as steel members are erected would fall under this subcategory.
6.2.2.3
Temporary Work and Support Activities (TWSA). This subcategory
includes all actions that must occur while activity-specific equipment is being used to erect and
secure a member into its final position. Attaching or adjusting rigging, setting up temporary
supports or wrapping a steel member with the hoist line to lift it into its final position would fall
under the TWSA subcategory. It also includes those actions needed to ensure that equipment in
use during the activity continues to work in the most optimal manner, such as replacing welding
rods when they are too short or refueling a scissors lift with gas.
Each NVAR activity provides an opportunity to redesign the process to eliminate or reduce the
NVAR component in a cycle. For example, one could redesign a building to allow for multiple
repetitions and reuses of formwork, thereby reducing the work content of the formwork activity.
Alternatively, one could redesign the structure to use precast foundation elements, thereby
eliminating the need for formwork altogether.
6.2.3 NVA (Waste Definitions)
Interest in lean construction has increased academic and industry interest in waste reduction in
construction. Waste reduction and elimination is one of the core principles of lean production,
and although it is not the only benefit of lean implementation, it does provide a logical starting
point. The potential cost and time savings achieved by eliminating or reducing NVA activities
are significant. Studies show that only 3 to 20 percent of tasks add value (Ciampa 1991), with
their share in total cycle time measuring between 0.5 and 5 percent (Stalk and Hout 1990).
Womack and Jones (1996) define waste as “…any human activity that absorbs resources but
creates no value.” The definition developed by Walbridge-Aldinger (2000) better conforms to
construction production; waste is defined “…as anything that takes time, resources or space but
does not add value to the product or service delivered to the customer.” To develop the construction production value stream, Ohno’s concepts of production will be modified to more
closely conform with construction production as follows:
•
Overproduction--Products being produced in excess quantities or products being
made before customers need them. This implies that production on a late-start
schedule is the ideal. Indeed, from the client’s viewpoint, if a late-start schedule
could be guaranteed in the face of weather, supplier schedules and other uncertainties, a late-start schedule would minimize WIP and cash flow requirements.
•
Waiting--Products, equipment or people that must wait because of poor
scheduling, production control or unbalanced crew size. Changing work tasks in
60
the course of a typical construction sequence make establishing a proper crew
composition difficult.
•
Transport--Unnecessary movement of materials. Material handling and transport
necessitated by the relocation of work are unavoidable in construction. This type
of waste includes excessive, multiple and suboptimal movements of material.
•
Extra Processing--Rework, rehandling or storage that is caused by defects in
design, fabrication or construction activities. This type of waste occurs within
crews.
•
Inventory--Extra raw or fabricated materials, excess construction equipment.
•
Motion--Extra movement by employees or movement of equipment caused by
inefficient layout, remote lay-down areas or improper work sequences.
•
Defects--Errors or deficiencies in finished products that require a crew to return
to a work item or require a follow-up crew to perform added work (punch list
items). This type of waste occurs between crews.
Table 6.1 compares the seven major classifications of waste in both manufacturing and
construction contexts.
6.3 Data Collection Procedure
A total of six value stream case studies were conducted as part of this research. Three cases
focused on structural steel erection and three cases focused on large bore pipe installation. For
each case study, operations were observed for two days. Two different methods were used to
gather value stream data. The first method (hand data collection) required one observer to
monitor each crew member in the observed crew. The second method (video data collection)
required two observers and two digital cameras to record each crew’s movements. Both methods
required data to be entered into spreadsheets so that the necessary tabular results could be
generated for each job. Figure 6.1 is an example of one of the data sheets used for the hand data
collection method.
6.3.1 Hand Data Collection Method
Each worker in a crew is represented in the first column of the data sheet. Names for each worker
were determined by the position that they were observed in during the various cycles. The
second column describes the specific building component that the worker was working on at a
specific point in an observation period. The third column represents the “real” clock time during
the observation period as measured from the first activity.1 The fourth column indicates the
activity observed for that specific time period. The fifth column shows the duration of time spent
on that activity. The sixth column specifies whether an activity is VA, NVAR or NVA. The
seventh column provides for a further subcategorization of each activity into one of the seven
wastes or one of the three subcategories of NVAR activities.
1
The time shown in Column No. 3 is not in temporal order because analysis of the data required each row
of information to be sorted.
61
Table 6.1: Comparison of Lean Manufacturing to Lean Construction Waste
Type of Waste
Manufacturing
Construction
1. Overproduction
Production of too many units or
parts due to push nature of
manufacturing.
Overbuilding a particular aspect of a
project, either because it was overengineered or a process was started
before it was really needed.
2. Waiting
Time spent waiting for the next
batch of parts to arrive from the
previous conversion process.
Time spent waiting for a machine
to finish.
Time spent waiting for other work
crews to finish their particular
conversion process so that the next
conversion process may begin. Time
spent waiting on crew members of a
specific team. Time spent waiting for
parts or instructions.
3. Transport
Wasted effort to transport
materials, parts or finished goods
into or out of storage between
processes.
Wasted effort to transport building
components or tools into or out of job
trailers or storage between processes.
4. Extra Processing
(Operations)
Doing more work than is
required.
Waste associated with rework, rehandling or storage caused by defects
in design, fabrication or construction
activities.
5. Inventory
Maintaining excess inventory of
raw materials, parts in process or
finished goods.
Maintaining excess inventory of
construction components, equipment
or tools.
6. Motion
Waste associated with
Waste associated with unnecessary
unnecessary worker/equipment
worker/equipment movement around
movement between work stations. the construction site.
7. Defects
Repair or rework.
Deficiencies in the finished product
that require additional work or rework
to correct punch list items.
62
FieldObservationSheet
CaseStudy#5
Date:
Personor Equipment: EntireGroupCycle#1
Worker
Member
Classification
Time
Activity
1/15/2003
Timeat
Activity
Waste
Activity Classification Classification
GroundCrewman#1 Column
1:13:12 Waiting
00:18
NVA
Waiting
1:14:50 Waiting
00:10
NVA
Waiting
1:51:40 Waiting
01:30
NVA
Waiting
1:13:30 PositioningColumnontoBasePlate
00:30
NVAR
Mat. Pos
1:50:40 PositioningColumnontoBasePlate
01:00
NVAR
Mat. Pos
1:17:12 ReleasingTagLine
00:48
NVAR
T.W.S.A.
1:14:00 BoltingColumnBase
00:50
VA
ValueAdding
GroundCrewman#1 PodBeamCombo
0:09:20 Walking
04:25
NVA
Motion
0:16:00 Walking
00:50
NVA
Motion
0:18:10 Walking
00:20
NVA
Motion
0:22:25 Walking
00:21
NVA
Motion
0:22:50 Walking
01:40
NVA
Motion
0:39:50 Walking
00:10
NVA
Motion
0:41:05 Walking
00:15
NVA
Motion
0:51:15 Walking
01:28
NVA
Motion
0:57:30 Walking
00:30
NVA
Motion
1:01:44 Walking
00:16
NVA
Motion
1:04:47 Walking
00:43
NVA
Motion
1:08:30 Walking
04:42
NVA
Motion
1:16:50 Walking
00:22
NVA
Motion
1:18:00 Walking
00:20
NVA
Motion
1:39:55 Walking
00:27
NVA
Motion
1:42:50 Walking
00:20
NVA
Motion
1:46:00 Walking
00:15
NVA
Motion
1:54:40 Walking
01:20
NVA
Motion
2:10:40 Walking
00:30
NVA
Motion
0:24:30 Movingequipment andtools (carryingtaglinefromprevious columnline)
01:08
NVA
Transport
01:20
NVA
Transport
01:25
NVA
Transport
00:40
NVA
Transport
01:40
NVA
Transport
0:54:08 Movingequipment andtools (movingdunage)
02:22
NVA
Transport
00:50
NVA
Transport
00:30
NVA
Transport
01:30
NVA
Transport
0:00:00 Waiting
00:20
NVA
Waiting
0:02:00 Waiting
05:20
NVA
Waiting
0:19:00 Waiting
02:30
NVA
Waiting
0:22:46 Waiting
00:04
NVA
Waiting
0:25:50 Waiting
02:10
NVA
Waiting
0:28:40 Waiting
08:00
NVA
Waiting
0:41:20 Waiting
02:10
NVA
Waiting
0:44:50 Waiting
03:50
NVA
Waiting
0:48:50 Waiting
01:00
NVA
Waiting
0:53:33 Waiting
00:35
NVA
Waiting
0:56:30 Waiting
01:00
NVA
Waiting
0:58:00 Waiting
01:25
NVA
Waiting
Figure 6.1: Hand Data Collection Sheet
63
Comments/Remarks
During the hand collection method, each observer was equipped with a stopwatch and a clipboard
containing data sheets. Data was recorded as the activities occurred. Each time a new task was
started, an entry was made on the data sheet. For example, an entry might indicate that a worker
was rigging a bar joist for the crane. The next entry might indicate that the worker was “waiting”
until the crane lowered its hook so that the rigging for the next bar joist could be attached. The
elapsed time for each task was recorded, as well as the observer’s judgment regarding whether the
task was “value-adding” to the process. A digital video camera was also used to record all
actions during the erection sequence. The videotapes were used to conduct a more detailed
analysis of the activities.
6.3.2 Video Data Collection
Video data collection required two observers each to operate a video camera. The digital video
cameras were positioned to view the activity area at right angles to provide “depth” in both
directions being viewed. In the lab, two televisions were placed next to each other and used to
view the recorded operations. Using both cameras provided a three-dimensional view of the
workspace. Viewing the tapes several times allowed one to record data on each of the observed
crew members.
Both the hand data collection method and the video data collection method worked satisfactorily.
Table 6.2 summarizes the advantages and disadvantages of each collection method.
6.4 Case Studies
The six case studies focused on two trades: the structural steel erection process and the large bore
pipe installation process. The structural steel erection process represents a process in which
cycles are relatively fast and repetitive. The structural steel cycles require large crews and heavy
equipment. The pipe spool installation process has opposite traits. Pipe installation is
characterized by long, nonrepetitive cycles. The spools often vary significantly from one to
another. The pipe crew can be quite small, and the tasks can be labor intensive
The following subsections provide a brief description of the case study projects and the cycle(s)
observed during the observation period. Site-specific information has been removed to prevent
disclosure of proprietary information. A complete analysis of each case study is presented in
Appendices A through F.
6.4.1 Case Study No. 1
Structural Steel Erection Job No. 1. The project was a 200,000 square foot structure, 660 feet
long and 300 feet wide. The entire area was divided into 55 bays, each measuring 60 feet by
60 feet. The team observed the erection activities associated with four bays. Hand data collection
was used.
Structural Steel Erection Job No. 2. The site included roughly 1,700 acres (another 300 acres
were reserved for future development). Several buildings will eventually occupy the site. The
case study focused on an area in the largest of these buildings. The structure was approximately
one million square feet and, when viewed from the plan view, resembled the shape of the letter
64
Table 6.2: Advantages and Disadvantages of Different Data Collection Methods
Data Collection Method
Advantages
Disadvantages
Real-Time Hand Collection
(Method No. 1)
Initial observations are
captured as they occur.
Minimal amount of time
required to record data.
Different interpretations of
waste categories occur
between the observation team
members.
Requires one observer per
member in the crew.
Digital Video Collection
(Method No. 2)
Observations outside of the
camera’s view are captured by
observation team members
(e.g., crew members may be
working on different cycles
outside of the camera’s view,
in which case data collection
method No. 2 might assume
the crew member’s activities
to be waiting).
Task durations sometimes
occur at such a rapid pace that
the initial observation may be
missed.
Allows for a more detailed
review of each cycle.
Limited by the camera’s view
of the cycle. Activities
outside the camera’s view are
not captured. Leaves room for
error.
Data collection process can be
accomplished with only two
observers.
Longer periods of time
required to analyze each crew
member’s action in a cycle.
65
“F.” The structure was composed of several smaller bay sections which roughly measured 60 feet
by 60 feet. The team observed the erection activities associated with two new bays performed by
one crew and the finishing activities of erecting purlins on top of a completed bay section done by
a second crew. Hand data collection was used.
Structural Steel Erection Job No. 3. Three main structures were being erected at this jobsite.
The total square footage for all buildings erected on this site was roughly 1.3 million. The
observation period focused on the largest of these structures, which accounted for more than half
of the total square footage. The structure was composed of several smaller bay sections, roughly
measuring 60 feet by 60 feet. The team observed the erection activities that occurred in four new
bays, with a focus on column, pod beam and spandrel beam erection for one crew, as well as the
erection activities associated with the bar joist members with a second follow-up crew.
Pipe Spool Installation Job No. 1. This project involved the installation of an auxiliary boiler in
an existing power plant. The housing for the boiler was located adjacent to the main power plant
boiler room. From the existing structure, four inch natural gas pipes and eight inch steam piping
were connected by a tee from the existing lines back to the new auxiliary boiler housed in the new
structure. Two separate areas were observed in this study. The focus in Area 1 was the
installation of an eight inch pipe spool approximately two feet long, a relief valve and an
eight inch elbow pipe spool approximately five feet long. All of the piping components observed
in Area 1 were prefabricated and had flanged/bolted connections. The focus of Area 2 was the
erection of an elbow pipe spool in a steam line that will be used as a bypass from the main
boiler’s steam line during down times.
Pipe Spool Installation Job No. 2. The project observed included the construction of a new
chemical processing plant. Several mechanical components and interconnecting pipes were being
installed during the observation period. The main focus during this study was the preparation and
welding of two sections of eight inch diameter prefabricated pipe into one large section. The case
study also included all activities required to lift the final spool into position and temporarily
support the spool section until its final supports could be erected/installed.
Pipe Spool Installation Job No. 3. This case study took place at a large manufacturing facility.
Several large structures were being erected around the site; the study was focused on the largest
of these structures. Unfortunately, during the observation period, several factors prevented the
team from observing VA activities so this became a “lessons learned” case study. This case study
highlights areas that, from the observation teams perspective, were not lean.
6.4.7 Data Analysis
The following section describes the process used to analyze the data for each case study. The
purpose of this section is to introduce the reader to the tables and figures located in the
appendices that show the individual and crew results for the various case studies. One or more
66
cycles were observed at each jobsite. A cycle was defined according to the nature of the work
being performed. The structural steel erection process involved three main cycles: column,
girder (beam) and joist (truss) erection. Because the erection process for structural steel is
repetitive, the research team was able to obtain several iterations for each cycle. On the other
hand, piping installation consists of long cycle times. For this reason, the cycles for process
piping were defined as one entire viewing period (i.e., the whole observation period). The
detailed case studies in the appendices provide additional information on the definition of each
cycle.
During each cycle, each individual crew member was evaluated to capture his or her specific
contribution to the various cycles. Each crew was also evaluated as a group to illustrate the
“crew’s value creation” during a cycle. Tables 6.3 and 6.4 show the tabulated results for a crew
member and a crew, respectively. Furthermore, Figures 6.2 and 6.3 graphically represent the data
in Tables 6.3 and 6.4. These results were obtained after all required information was entered into
the data collection spreadsheet for each worker (refer to Figure 6.1). Table 6.3 and Figure 6.2
show the typical results for an individual worker in a cycle. The first column lists each work
category (i.e., VA, NVAR and NVA). In some cases, a worker may not dedicate any time to a
specific work category; this results in the category not being shown at all. The second column
associates each activity with the specific waste category. The third column represents the total
time in a cycle that the crew member spends on a specific waste category. The final column
represents the percentage of the total time a worker spends on each waste category in a cycle.
Showing this level of detail allows one to better understand what is happening during the
construction process. Additionally, analysis at this level of detail highlights areas where
improvement efforts should be focused. For example, time wasted on waiting is typical in a crew
that has unbalanced work assignments. To address this problem, the required work tasks could be
more evenly dispersed throughout the crew or in some cases, crew members could be eliminated.
Table 6.3: Typical Results for Welder Completing an Eight Inch Diameter Spool Section
Activity Classification
VA
Waste Classification
Time at Activity
% of Time at Activity
Value Adding
1:24:11
1:24:11
24.58
24.58
Waiting
Extra Processing
Transport
Motion
1:42:37
0:36:28
0:25:23
0:55:21
3:39:49
29.96
10.65
7.41
16.16
64.18
Material Positioning
In-Process Inspection
TWSA
NVAR Total
0:05:33
0:16:17
0:16:40
0:38:30
1.62
4.75
4.87
11.24
Grand Total
5:42:30
100.00
VA Total
NVA
NVA Total
NVAR
67
Table 6.4: Typical Results for an Entire Crew
10:40:25
VA
Crew Member
Foreman - Pipe Fitter
Field Laborer
Welder
Group Percentage
Waste
Extra
All
Activities Waiting Processing Transport
NVAR
Material
Movement Pos.
In Proc.
Ins.
TWSA
Total
VA +
NVAR
0%
0%
25%
19%
52%
30%
10%
21%
11%
6%
5%
7%
22%
2%
16%
12%
2%
2%
18%
1%
5%
14%
16%
100%
100%
44%
20%
5%
100%
36%
13%
30%
12%
7%
15%
5%
8%
10%
100%
36%
Figure 6.2: Typical Results for Welder Completing an Eight Inch Diameter Spool Section
68
Figure 6.3: Typical Results for an Entire Crew
When the entire crew was evaluated, each crew member’s individual results were combined with
those of other crew members. Table 6.4 and Figure 6.3 show the typical results for an entire crew
during one typical cycle. In the upper right corner of Table 6.4, the cumulative time spent by the
crew on the specific work element is shown. The first column lists each worker involved in the
crew, along with the entire crews’ weighted average values on the bottom. For each worker, the
percentages shown are based on the total time that each crew member contributed to the cycle,
not the total cumulative time shown in the upper right corner. This was done because unequal
amounts of time were spent on a cycle by various crew members. Furthermore, if one person was
involved in a cycle longer than another, their time should affect the weighted average values the
most. The next column shows the percentage of time that a crew member contributed toward VA
actions. Columns 3 thru 6 represent each NVA subcategory. Columns 7 thru 9 represent the
three subcategories associated with NVAR actions. The tenth column verifies that all of the
individual crew member’s time in a cycle was accounted for. The remaining column (11) shows
the total percentage value for VA time and NVAR time committed by that crew member to the
building component. Notice that only four of the seven types of waste are represented in these
tabular results.
6.5 Value Stream Analysis Results
In the following subsections, the results for each case study are discussed, and comparisons are
made among across similar processes. Observations are then made about the differences between
the structural steel value stream and the large bore piping value stream.
69
6.5.1 Structural Steel Case Studies
Case Study No. 1 (Appendix A) involved the erection process for light-gauge structural steel.
This study examined the extended control the contractor had on the value stream. The contractor
controlled all aspects of material purchasing, delivery and erection proceedings. The material
element of the value stream included when it was shipped, how it was shipped and the level of
organization in which steel was placed on the ground prior to the erection process. The
contractor controlled the labor component by specifying the number of workers per crew and the
specific tasks each worker was responsible for during the erection cycle. Table 6.5 shows the
results from the observation period.
Table 6.5: Results for Case Study No.1 - Structural Steel Erection Process2
VA
Value Adding
VA Total
Total Time at Activity
% of Total Time
2:51:04
24.89%
2:51:04
24.89%
1:26:53
0:02:58
12.64%
0.43%
NVAR
Mat. Pos.
In-Process-Ins.
T.W.S.A.
NVAR Total
1:00:44
8.84%
2:30:35
21.91%
3:12:03
0:41:04
0:15:28
1:56:56
27.95%
5.98%
2.25%
17.02%
NVA
Waiting
Extra Proc.
Transport
Motion
NVA Total
Grand Total
6:05:31
53.19%
11:27:10
100.00%
Table 6.6 shows the Quick Summary results from the value stream map for Case Study No. 1. Of
the 792 total workable hours committed to the steel erection process, only 161 were VA.
Table 6.6: Quick Summary for Case Study No. 1
Quick Summary for Level One
Working Days
24 days
Working Time
792 man-hours
VA Total
161 man-hours
NVAR Total
95 man-hours
NVA Total
536 man-hours
Case Study No. 2 involved the erection process for heavy-gauge steel. Large joist girders and
trusses were required for the structural steel skeleton of the facility. The main point of interest for
this study was the material delivery process. The contractor was restricted to delivering only one
phase (three to six bays) of steel ahead of the erection crew; the delivery process resembled a JIT
delivery system. However, the current delivery system was put in place after the original system
of unrestricted deliveries had created safety issues. A direct result of this restriction was the low
inventory days required for each phase. The contractor controlled the movement of steel from the
manufacturer’s facility to its storage position in the parking lot and, finally, to the material laydown area. A separate subcontractor controlled the labor portion for erecting the steel, as well as
the steel movement from the lay-down area into its final position. Table 6.7 portrays the results
from the observation period.
2
The crane operator’s time was not included in this analysis because one member of the data collection
crew was called away. However, had his time been included it would have shown that the VA/NVA “% of
Total Time” values dropped slightly, and the NVAR percentage values acquired the difference.
70
Table 6.7: Results for Case Study No. 2 - Structural Steel Erection Process
VA
Time at Activity
Value Adding
1:00:18
10.54%
1:00:18
10.54%
1:21:51
2:00:56
14.31%
21.14%
3:22:47
35.45%
2:18:55
0:22:42
0:41:40
1:45:42
24.28%
3.97%
7%
18.48%
NVA Total
5:08:59
54.01%
Grand Total
9:32:04
100%
VA Total
NVAR
Mat. Pos.
T.W.S.A.
NVAR Total
NVA
Waiting
Extra Proc.
Transport
Motion
Table 6.8 shows the Quick Summary results from the value stream map for Case Study No. 2. Of
the 2,016 total workable hours committed to the 14 phases of the steel erection process, only 181
were VA.
For One Phase (three to six bays)
Working Days
4
Working Days
Work Time
144 man-hours
Work Time
VA Total
13 man-hours
VA Total
NVAR Total
48 man-hours
NVAR Total
NVA Total
83 man-hours
NVA Total
For 14 Phases
56
2016
181
674
1162
man-hours
man-hours
man-hours
man-hours
Case Study No. 3 involved the erection process for light-gauge steel. The main point of interest
for this case study included the use of two separate crews to erect the various steel elements. For
this project, the subcontractor controlled the entire labor value stream and a portion of the
material value stream after the steel had been delivered to the site. The contractor controlled the
portion of the material value stream from procurement to delivery of the steel onto the site. The
subcontractor chose to use two crews for the production process. One crew was responsible for
erecting columns and pod beam combinations (pod beam and spandrel beam connected as one
unit). The second crew was responsible for erecting the interleaving bar joists for each bay. The
design of this multiple crew system was closer to a lean manufacturing ideal. The higher density
of workers provided higher throughput and a smaller amount of WIP. However, while the
process was fast, adding new crew members to the production process caused waste attributed to
“waiting” that consumed nearly half of the total time because of synchronization problems
between Crew 2 and Crew 1. Table 6.9 shows the results from the observation period.
Table 6.9: Results for Case Study No. 3 - Structural Steel Erection Process
VA
Value Adding
VA Total
% of Total Time
2:04:45
9.77%
2:04:45
9.77%
NVAR
Mat. Pos
2:00:32
9.44%
In-Process Ins.
T.W.S.A.
0:06:15
3:10:01
0.49%
14.89%
5:16:48
24.82%
9:41:12
0:08:09
0:59:17
3:06:19
45.53%
0.64%
4.64%
14.60%
NVAR Total
NVA
Waiting
Extra Proc.
Transport
Motion
NVA Total
13:54:57
65.41%
Grand Total
21:16:30
100.00%
71
Table 6.10 shows the Quick Summary results from the value stream map for Case Study No. 3.
Of the 1,544 total workable hours committed to the steel erection process, only 152 were VA.
Working Days
37
Working Time
1544 man-hours
VA Total
152 man-hours
NVAR Total
373 man-hours
NVA Total
1018 man-hours
6.5.1.1 Comparison of Structural Steel Cases. Case Studies No. 1 and No. 3 offer
insight into to the effects of crew variation in a steel erection process. Material on both sites was
organized in a similar fashion. The main difference between these studies was the additional
erection crew in Case Study No. 3. Lean ideology requires balancing processes to create flow in
the value stream. Flow was generated in Case Study No. 3 at the crew level. In Case Study
No. 3, no back-tracking was required such as that observed during Case Study No. 1 (crew
erected two columns and girders, then backtracked to erect bar joists). While the erection process
proved to be faster compared to Case Study No. 1, the waste attributed to waiting nearly doubled
for Case Study No. 3. Similar complications resulting from unbalanced crewmember responsibilities were present in each study. Three lessons were learned from this comparison:
(1)
Introducing two (or more) crews to the erection process does not necessarily
create additional value, even though it does increase throughput and reduce WIP.
Multiple ill-designed crews only increase the rate at which waste is accumulated.
The VA percentage dropped from 25 percent for Case Study No. 1 to roughly
10 percent for Case Study No. 2.
(2)
Adding another crew to the process can add waste to the value stream if the work
progress of the individual crews is not synchronized. The increase of NVA
percentages from 53 percent (Case Study No. 1) to 65 percent (Case Study No. 3)
highlights this effect.
(3)
Even though VA percentages dropped at the project level, the reduction in
overproduction (WIP) and inventory wastes, as viewed from the owner’s
perspective, may offset the decrease in the VA percentage (i.e., the project is
completed earlier, thus allowing income to be generated earlier from a finished
facility).
Comparing Case Study No. 2 to Case Studies No. 1 and No. 3 shows the effect structural design
has on a value stream. The light-gauge steel in Case Studies No. 1 and No. 3 required smaller
amounts of NVAR actions (21.9 and 24.8 percent, respectively) than the heavier-gauge steel for
Case Study No. 2 (35.5 percent). More actions were required during Case Study No. 2 to safely
hoist and secure each structural element into its final position. A decrease in the NVA percentage
would have been shown had material organization in the lay-down area been different in Case
Study No. 2 (i.e., offloading steel elements from the truck to a position on the ground next to their
final place in the structure).
72
The largest VA percentage (24.9 percent) was found in Case Study No. 1 and the smallest
(9.8 percent) in Case Study No. 3. The largest NVAR percentage (35.5 percent) was found in
Case Study No. 2 and the smallest (21.9 percent) in Case Study No. 1. The largest NVA percentage (65.45 percent) was found in Case Study No. 3 and the smallest (53.2 percent) in Case Study
No. 1.
6.5.2 Process Piping Case Studies
Case Study No. 4 (Appendix D) involved the installation process for eight inch diameter piping
components. Two points of interest were highlighted in this case study. First, the contractor
controlled all aspects of the material and labor value streams. Second, the observations included
both prefabricated and field-fabricated piping processes. This second point was of particular
interest because it highlighted the different labor requirements for each piping process. The
prefabricated spool and valve installation process required one fifth of the time needed to field
fabricate and install pipe spools using a similar crew structure. The VA percentage was
18 percent for the prefabricated process and 8 percent for the field-fabricated process. The
weighted VA, NVAR and NVA percentages for the entire observation period are shown in
Table 6.11. Notice the large value for pure NVA waste (Type II muda).
Table 6.11: Results for Case Study No. 4 - Piping Installation Process
VA
Value Adding
Time at Activity
1:14:07
10.43%
1:14:07
10.43%
Mat. Pos.
1:26:55
12.23%
In-Process Ins.
T.W.S.A.
0:16:00
0:49:11
2.25%
6.92%
2:32:06
21.40%
VA Total
NVAR
NVAR Total
NVA
Waiting
3:14:31
27.37%
Extra Proc.
Transport
1:37:57
1:16:51
13.78%
10.81%
Motion
NVA Total
Grand Total
1:55:08
16.20%
8:04:27
68.17%
11:50:40
100.00%
Of the 1,267 total workable hours committed to the piping installation process, only 98 were VA.
For All Spools Worked on During
Observation Period
Working Days
33
Working Time
1267 man-hours
VA Total
98 man-hours
NVAR Total
266 man-hours
NVA Total
904 man-hours
Case Study No. 5 (Appendix E) involved the installation of prefabricated pipe spools. The major
point of interest for this study was the cause and effect relationship between the material and
labor value streams. Multiple parties controlled the material value stream before the
prefabricated spools were shipped to the site (e.g., spool fabricator, cleaning and painting
subcontractor). The contractor oversaw the movement of material between each party. The
73
installing subcontractor controlled the material value stream once it was delivered to the site. The
installing subcontractor controlled all aspects of the labor value stream as well. Obstructed
information flow between the various parties resulted in a large extra processing percentage (e.g.,
paint was ground off each end of the delivered spools from the painting subcontractor).
Table 6.13 shows the weighted average values for the entire installation period.
Table 6.13: Result for Case Study No. 5 - Piping Installation Process
VA
Time at Activity
Value Adding
VA Total
1:24:11
8.19%
1:24:11
8.19%
NVAR
Material Pos.
0:39:13
3.82%
In-Process Ins.
T.W.S.A
1:21:47
1:15:48
7.96%
7.38%
3:16:48
19.15%
5:15:40
3:13:17
1:19:17
30.72%
18.81%
7.72%
NVAR Total
NVA
Waiting
Extra Proc.
Transport
2:38:17
15.40%
NVA Total
Motion
12:26:31
72.65%
Grand Total
17:07:30
100.00%
Of the 800 total workable hours committed to the piping installation process, only 58 were VA.
Observation Period
Working Days
35
Working Time
800 man-hours
VA Total
58 man-hours
NVAR Total
153 man-hours
NVA Total
590 man-hours
In Case Study No. 6 (Appendix F) installation of Victaulic pipe was observed. No VA actions
were observed during this visit. The observation period was not representative of the site’s
average work distribution values; therefore, only a “lessons learned” synopsis for Case Study
No. 6 is included.
6.5.2.1 Comparison of Piping Process Cases. Greater control of the process piping
value stream in Case Study No. 4 resulted in the best average work distribution values.
Comparing only the VA percentages from the prefabricated spool processes of each job shows
that there was a net difference of 10 percent (18 percent from Case Study No. 4, 8 percent from
Case Study No. 5). Furthermore, the VA percentage from Case Study No. 5 for prefabricated
spools more closely resembles the field-fabricated values found in Case Study No. 4. When the
value stream is not monitored at the level required, defects pass through the value stream; the
final erection crew was required to fix all upstream defects. These defects were the cause for the
lower VA percentage of the prefabricated spool installation in Case Study No. 5.
Both cases included extra processing (rework) wastes. More than two thirds of the installation
processes resulted in pure waste (NVA). Also, the VA percentage for process piping ranged from
8 to 10.5 percent. Finally, defects pushed through the value stream that required rework on the
74
part of the crew caused variations from the expected work distribution values and the actual work
distribution values.
6.5.3 Comparison of Processes
Table 6.15 compares the weighted average work values found for each case study. Excluding
Case Study No. 1, the majority of processes analyzed in this report resulted in VA percentages
between 8 and 10.5 percent. In other words, at the production level, the typical construction
production process was found to contain from 8 to 10.5 percent VA actions. At best, for a simple,
highly repetitive process, a contractor (one who is trying to apply lean principles) attained a VA
percentage of 25 percent. The objective of a typical lean manufacturing company, in contrast, is
to achieve 75 percent VA activities on an entire assembly line. The construction industry realizes
one sixth (at worst) to one third (at best) of the VA time of the manufacturing industry. Table
6.15 also shows that process piping jobs incur higher percentages of pure waste (NVA) in the
production process. Specifically, the piping production process contributes larger amounts of
time to transport and extra processing waste than does the steel production process. This extra
processing is directly related to defects occurring upstream in the piping value stream.
Table 6.15: Comparison of Different Processes
On average, steel production processes require more NVAR actions than do piping processes. A
large contributor to the steel process NVAR category is material positioning. Because steel
erection processes are more repetitive than piping processes, more time is spent on the act of
aligning each new member into a final position. More time is also required in the steel erection
process for TWSA. However, NVAR waste due to in-process inspections is more typical for
piping processes than for steel processes.
6.5.3.1 Limitations of this Study. The value streams for each case study represent only
those elements specific to the process observed. To map out the entire value stream for the
construction production process, the job would need to be monitored in its entirety. For example,
Toyota’s entire value stream related to its production process can be observed in one day (i.e., a
car takes one full day to go from start to finish). Therefore, to view the entire value stream for a
construction production process, the process must be observed from the start of the project
through completion.
75
6.5.4 Value Stream Analysis
What can be learned from the results of the construction value stream analysis? First, the value
stream map is flexible enough to accommodate two very different construction processes, and
since most construction processes fall between these extremes, the value stream map is capable of
representing most, if not all, remaining processes. Second, by implementing the value stream
map, a systematic approach to identifying problem areas in the production process can be created.
If the problem is not caused at the production level, the value stream map will highlight the
bottlenecked area.
One generalization is obvious. In construction, NVA activities consume between 50 and
75 percent of the productive time on the job. It is worthwhile to note that this percentage was
derived from crews doing direct work. Many crews on the typical jobsite perform indirect work
(warehousing, laydown and cleanup). If their work efforts were included, the NVA percentage
would certainly rise. NVAR work on the typical construction job consumes between 20 and
25 percent of the productive time. This is much higher than that experienced at the typical
manufacturing plant. A high fraction of NVAR work is expected in construction because of the
nature of the work and the fact that it is performed in relatively uncontrolled environments.
It also seems obvious that the construction industry should take advantage of the ability to reduce
the NVA component of construction value streams. This can be done by working to balance
crews and to make work tasks and task times more predictable. Assigning crews of the
appropriate size and eliminating double and triple handling of materials will also help reduce the
NVA component. Significant gains can be realized by reducing the NVAR component.
However, this will require changes that are broader in scope. Some changes to erection/assembly
techniques will need to be made if the frequency of in-process inspection is to be reduced.
Changes to design will be needed to enable less reliance on temporary supports. More work with
suppliers will be necessary to eliminate excess material positioning time. Finally, improving VA
times will require changes in project design to provide for more repetition, more standardization
and more preassembly and prefabrication.
Perhaps the greatest contribution of these value stream studies is to demonstrate in an objective
way how much improvement is possible in construction value generation.
6.6 Identifying Construction’s Value Stream
There are two aspects one must investigate to identify waste on a construction site. The first
involves the material required to construct a facility. The second entails the multiple activities
required for the installation of material into its final position. Each aspect of the value stream
occurs on a different time scale. The material value stream includes all materials that are
delivered to the site in a “post” manufactured state, such as a structural columns or the bolts
required to secure that column into place. Piping material might be a pipe spool or a welding rod.
In short, materials include everything that will remain with the facility after the construction
phase is completed.
The labor aspect of the value stream encompasses all labor required to erect and install material
into its final position. Closely associated with labor is construction equipment. For every piece
of equipment on a construction site, there is a human operator. Workers along with machines will
bolt, frame and weld components into their final position. Workers, aided by machines, add
76
value to the final product. How much value they are capable of adding depends upon management, work processes, information flow and the skill of the crews.
According to the definitions of waste, waiting, transport, extra processing and motion are most
closely related to the actual work process (i.e., labor and equipment). Overproduction, inventory
and defects are associated with the material supply chain and production scheduling functions.
The observation periods for each case study were brief and focused, which limited the team’s
ability to quantify wastes associated with overproduction, inventory and defects in specific detail.
6.7 Developing a Construction Value Stream Map
As demonstrated in Chapter 3.0, construction is different from manufacturing. One can assume
that a value stream representation for a construction process will likewise be very different from
one for a manufacturing value stream. Review of value stream mapping in manufacturing is a
useful starting point for developing value stream mapping in construction. Duggan and Liker
(2002) expand on procedures developed by Rother and Shook (1998) for value stream mapping
models of manufacturing plants. In a typical plant, the material would flow in one side and
proceed through the various processes (stamping presses, grinders, paint shops, etc.) to produce
the finished product required by the customer. Viewed in its entirety, this model represents a first
in first out (FIFO) process. While this idea does accommodate many manufacturing processes, it
does not relate as well to a typical construction jobsite. Duggan and Liker took this idea and
expanded it to include manufacturing plants that have multiple inputs coming together through
the same value stream to produce a variety of outputs (products). This process is further
identified as mixed model production. In the Duggan and Liker mixed model production, two
new concepts are found that aid in the development and implementation of the value stream on a
construction site. The first concept requires one to look at activities in a value stream not at the
individual level, but rather at the value stream as a mix of activity groups labeled by Duggan as
“product families.” The second concept builds on the first by requiring one to focus on the
“total” time associated with the product families, rather than on the individual times required for
each product. For the purpose of this study, “products” will be considered to be “processes.” In
other words, the construction value stream at the topmost level will be represented through a
series of process families. Duggan and Liker define product family as “a group of products that
pass through similar processes or equipment and have similar work content.” For construction, it
can be said that a process family is a group of processes that require similar crew members or
equipment and have similar work content. For example, a process family incorporates all
subtasks required to take a structural/piping member from the material lay-down yard on a site,
through its final preparation stages and into its final position in the facility. The following section
describes the steps one should take to create a value stream map.
6.8 Building a Value Stream Map
The conventional method used to create value stream maps was developed specifically for the
manufacturing industry. This conventional approach was used as a point of departure for
developing a construction value stream mapping process. Figure 6.4 shows how a value stream
for a structural steel erection process would be depicted using the conventional manufacturing
method (Tapping, Luyster et al. 2003). This method cannot accommodate the multiple variables
of a construction value stream. To overcome this difficulty, the conventional manufacturing
value stream map has been modified to match construction industry characteristics.
The typical manufacturing approach identifies all elements in the value stream. The arrows
represent the flow of material and/or information through the production line. The logic
progresses from the left to right, with each box representing a different stage in the production
77
line. For this study, the production line has been limited to the highly repetitive process of
erecting bar joists. The flow in this map begins when steel members are ordered from the
manufacturer. They are then shipped to the jobsite and stored onsite before erection. Finally, the
map shows the individual substages that each crew member participates in during the erection of
the bar joist members.
A construction value stream cannot be represented like a manufacturing value stream. The major
difference between the two systems occurs at the project level when material reaches the site.
Material on the construction site does not flow past the worker, rather the worker must move
(flow) to the material. In manufacturing, the “work station,” where a transformation of the final
product occurs, never has to move in the “ideal” manufacturing line, yet for a construction
process the “work station” continually moves around the jobsite as work progress. Furthermore,
the conventional model on Figure 6.4 assumes a linear relationship between its elements, creating
what is known as a FIFO process. In construction, several tasks in an activity can and/or must
occur simultaneously. The simple manufacturing value stream model does not easily allow for
parallel activities.
6.9 New Approach to Value Stream Mapping
This report focused on defining “process family” activities and measuring the time that it took to
transform materials (post-fabrication), beginning with procurement, through the construction
phase and ending with the turnover of the facility to the owner in its finished state. Figure 6.5
shows the new value stream map in its entirety for the structural steel erection process.
Modifications have been introduced in this new map to better represent processes dealing with
multiple variables (inputs or outputs), as well as multiple activities occurring at the same time in
each stage. The new format separates the conventional manufacturing value stream into three
levels. Level One includes the main stages material must go through for installation. Both
information flow and material movement are represented at this level in the value stream. The
second level expands the main stages in Level One to show substages that occur simultaneously
to complete each main stage. Level Two is useful for showing the multiple phases a material
element might go through during a process-specific value stream. Furthermore, it allows one to
see where most of the time in a stage is spent and can even highlight steps in a process that need
special attention. Finally, Level Three details the various crew members associated with each
substage displayed in Level Two. The contribution of each crew member to the VA, NVAR and
NVA categories are displayed for each substage in these tables. The following sections describe
the details of this value stream map, beginning with Level Three, and explain how each sublevel
relates to the one above.
6.9.1 Level Three
Level Three, shown in greater detail on Figure 6.6, consists of three main elements. Area 1
(circled on the figure and labeled Area 1) includes a different table for every major task observed
during the case study. Level Three details how much time each crew member contributed to the
waste category. The specific wastes Level Three details are waiting, extra processing, transport,
and movement. Furthermore, one can see if a crew was sized correctly to minimize waste caused
by waiting. If a worker was waiting for the majority of all tasks, it would be beneficial to the
crew’s productivity to redesign the tasks to eliminate the need for that member. In addition, if
one observed that the majority of the work was carried out by one worker, then balancing the
individual crew member responsibilities more evenly across the crew would be appropriate. The
last table in Area 1 shows the weighted averages of the crew for all tasks. These weighted
averages were combined to create VA, NVAR and NVA total values for the crew shown in
Area 2.
78
Production Control
Every 1-3 days
Project Engineer
1 Order for all Bar Joist
Project Feedback
Project
Superintendent
Percent Complete
Steel In
Place
awaiting
welding
Steel
Supplier
As Required
2 Shipments
O
Daily
O OO
Forklift
Operator
Fifo
Forklift
Operator
Fifo
Forklift
Operator
Fifo
Forklift
Operator
Fifo
Forklift
Operator
Staggard
Ground
Crewmen
Staggard
Left
Connector
Staggard
Left
Connector
Staggard
Right
Connector
Staggard
Right
Connector
Staggard
X-Bracing
Connector
Staggard
X-Bracing
Connector
Staggard
CT=
CO=
CT=
CO=
CT=
CO=
CT=
CO=
CT=
CO=
CT=
CO=
CT=
CO=
CT=
CO=
CT=
CO=
CT=
CO=
CT=
CO=
CT=
CO=
Uptime
Uptime
Uptime
Uptime
Uptime
Uptime
Uptime
Uptime
Uptime
Uptime
Uptime
Uptime
Avail
time
Avail
time
Avail
time
Avail
time
Avail
time
Avail
time
Avail
time
Avail
time
Avail
time
Avail
time
Avail
time
Avail
time
Figure 6.4: Traditional Value Stream Map
79
Production Control
Project Engineer
Every 1-3 days
Triggering Event
Level One
2 phases of steel are ordered
Percent Complete
Project Superintendent
Distribution of time from VSM
Steel In Place awaiting welding
Time Allocation Field
NVA Time
Project Feedback
Steel Supplier
NVAR Time
1
Daily
As Required
VA Time
Work Time
5 cumulative days to deliver steel
O
OO
0
O
100
200
300
400
500
600
700
800
Manhours
Stage One - Steel is offloaded in
respective Bays
Days Required
Stage Two (A,B) - Steel Shake
out Process
Days
5
Required
2
Equipment involved:
Forklifts
Workers involved
Crew
WT
VA ( 0%)
NVAR (20%)
NVA (80%)
Stage Three - Steel Erection Process
Days Required
Equipment involved:
2
Forklifts
32
0
6.4
25.6
1
Workers involved
Crew
WT
VA ( 0%)
NVAR (0%)
NVA (100%)
2
Inv
2
80
0
0
80
8
Stage Two (B) - Specific Bar
Joists and girders are pulled from
Days
2.5
Required
Equipment involved:
Stage Two (A) - Bar Joists
bundles are shook out
Days
2.5
Required
Equipment involved:
1
Forklifts
Workers involved
Crew
WT
VA ( 0%)
NVAR (0%)
NVA (100%)
Forklifts
2
40
0
0
40
Columns
Crew Member
Fork Lift Operator
Level Three Ground Crewmen
Left Connector
X-Bracing Con.
Right Connector
Group Percentage
6%
Waiting
14%
0%
40%
66%
53%
35%
Waste
Extra
Transport
Processing
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
0%
NVA Sum
0%
61%
Crew Member
Fork Lift Operator
Ground Crewmen
Left Connector
X-Bracing Con.
Right Connector
Group Percentage
VA
All
Activities
0%
0%
16%
0%
16%
8%
Waiting
66%
0%
12%
87%
24%
47%
Waste
Extra
Transport
Processing
0%
3%
0%
0%
44%
0%
0%
0%
60%
0%
0%
27%
NVA =
77%
Fork Lift Operator
Ground Crewmen
Left Connector
X-Bracing Con.
Right Connector
Group Percentage
VA
All
Activities
25%
0%
41%
57%
25%
31%
Waiting
24%
40%
16%
11%
27%
34%
Waste
Extra
Transport
Processing
5%
12%
0%
4%
0%
0%
0%
0%
0%
0%
4%
NVA =
Steel Erection - Entire Process
VA
Crew Member
All
Waiting
Activities
Fork Lift Operator
17%
28%
Ground Crewmen
0%
40%
Left Connector
32%
17%
X-Bracing Con.
38%
35%
Right Connector
21%
29%
Group Percentage
25%
28%
9%
60%
2
40
0
0
40
6%
2%
Days Required
Crane, 2
Skylift, Forklift
Workers involved
Crew
WT=
VA ( 8%) =
NVAR (15%) =
NVA (77%) =
5
78.7
4.7
26.8
47.2
1:19:32h:m:s
16%
0%
46%
34%
18%
26%
7%
Total %
VA +
NVAR %
100%
0%
100%
100%
100%
70%
0%
13%
0%
29%
100%
34%
2:10:31h:m:s
39%
In Proc. Ins.
T.W.S.A
4%
0%
0%
0%
0%
52%
0%
0%
0%
0%
2%
24%
NVAR
11%
0%
2%
1%
0%
Material
Pos.
6%
0%
27%
0%
0%
3%
9%
Movement
In Proc. Ins.
T.W.S.A
Total %
VA +
NVAR %
0%
0%
0%
0%
0%
14%
0%
0%
12%
0%
100%
0%
100%
100%
100%
21%
0%
42%
12%
16%
6%
101%
23%
0%
15%
7:57:07h:m:s
NVAR
20%
0%
16%
30%
22%
Material
Pos.
4%
18%
27%
0%
24%
13%
1%
Movement
In Proc. Ins.
T.W.S.A
Total %
VA +
NVAR %
1%
0%
0%
0%
0%
8%
38%
0%
3%
2%
100%
100%
100%
100%
100%
39%
56%
68%
60%
51%
3%
99%
40%
5%
9%
11:27:10h:m:s
NVAR
In Proc. Ins.
T.W.S.A
Total %
VA +
NVAR %
2%
0%
0%
0%
0%
19%
38%
0%
5%
2%
100%
100%
100%
100%
100%
43%
56%
57%
42%
42%
9%
100%
46%
18%
0%
16%
23%
17%
Material
Pos.
5%
18%
25%
0%
19%
17%
13%
0%
% of Total
Time
% of Total Time
each steel
element requires
Movement
Table represents the time distribution for each element viewed during the observation period
Cumulative
Number of
Cycle time for each
Time for
members
Cumulative Time for each Element
element installed
various
observed
categories
1:19:32
2
0:39:46
Total cumulative Time for two columns
Total Cumulative Time for 2 Girders
2:10:31
2
1:05:15
Total Cumulative Time for 26 Bar Joists
7:57:07
26
0:18:21
Total Time
11:27:10
12%
19%
69%
Average VA Percentage
Average NVAR Percentage
25%
22%
Average NVA Percentage
53%
5.8%
9.5%
2.7%
Figure 6.5: Structure for a New Value Stream Map
80
3.2
Equipment involved:
NVAR
Material
Pos.
7%
0%
0%
0%
29%
Movement
NVAR =
Total Cumulative Time for Steel Erection
Waste
Extra
Transport
Processing
3%
8%
0%
4%
11%
0%
0%
0%
12%
0%
Joist Girder is erected
2.0
2
Workers involved
Crew
WT=
VA ( 6%) =
NVAR (34%) =
NVA (60%) =
NVAR =
Total Cumulative Time Spent on Bar Joists
Bar Joists
Crew Member
Crane, Forklift
NVAR Sum
Total Cumulative Time Spent on Girders
Girders
Summary of all stages in Level 1
Working Days
24 days
Woking Time
792 man hours
VA Total
161 man hours
NVA Total
95 man hours
NVAR Total
536 man hours
10
Equipment involved:
Total Cumulative Time Spent on Columns
VA
All
Activities
7%
0%
13%
0%
0%
2 to 4
Columns Erected
Days Required
1
Workers involved
Crew
WT
VA ( 0%)
NVAR (0%)
NVA (0%)
**Graph shows the amount of man-hours atributed to each work category. VA time +
NVAR time + NVA time = Work Time
17.0
680
161
89
430
Inventory Days
10
Note: These Steps occur at the same time. Columns and
Girders are erected first but cannot be continued until the
inner supporting bar joist have been erected.
Inv
2
Level Two
Equipment involved:
Forklift, crane,
skylifts
Workers involved
Crew
WT=
VA ( 7%, 13%)
NVAR (28%, 21%)
NVA (100%)
4
5
129.2
10.3
19.4
99.4
Bar Joist installed along
with x-bracing members
Days Required
11.8
Equipment involved:
Crane,
Forklift, 2
4
Skylifts
Workers involved
Crew
5
WT=
472
VA ( 31%) =
146
NVAR (9%) =
42
NVA (60%) =
283
Columns
Crew Member
Level Three
Fork Lift Operator
Ground Crewmen
Left Connector
X-Bracing Con.
Right Connector
Group Percentage
VA
All
Activities
7%
0%
13%
0%
0%
6%
Waiting
14%
0%
40%
66%
53%
35%
NVA Sum
Girders
Crew Member
Fork Lift Operator
Ground Crewmen
Left Connector
X-Bracing Con.
Right Connector
Group Percentage
VA
All
Activities
0%
0%
16%
0%
16%
8%
Waiting
66%
0%
12%
87%
24%
47%
NVA =
Bar Joists
Crew Member
Fork Lift Operator
Ground Crewmen
Left Connector
X-Bracing Con.
Right Connector
Group Percentage
VA
All
Activities
25%
0%
41%
57%
25%
31%
VA
Crew Member
All
Activities
Fork Lift Operator
17%
Ground Crewmen
0%
32%
Left Connector
38%
X-Bracing Con.
21%
Right Connector
Group Percentage
25%
Waiting
24%
40%
16%
11%
27%
34%
NVA =
Waiting
28%
40%
17%
35%
29%
28%
Waste
Extra
Transport
Movement
Processing
0%
0%
16%
0%
0%
0%
0%
0%
46%
0%
0%
34%
0%
0%
18%
1:19:32 h:m:s
NVAR
Material
Pos.
7%
0%
0%
0%
29%
70%
0%
13%
0%
29%
100%
34%
2:10:31 h:m:s
39%
52%
0%
0%
0%
0%
0%
0%
26%
7%
2%
NVAR Sum
Waste
NVAR
Extra
Material
Transport
Movement
In Proc. Ins.
Processing
Pos.
0%
3%
11%
6%
0%
0%
0%
0%
0%
0%
44%
0%
2%
27%
0%
0%
0%
1%
0%
0%
60%
0%
0%
0%
0%
24%
0%
3%
9%
0%
NVAR =
15%
Waste
NVAR
Material
Extra
Movement
In Proc. Ins.
Transport
Pos.
Processing
5%
12%
20%
4%
1%
0%
4%
0%
18%
0%
0%
0%
16%
27%
0%
0%
0%
30%
0%
0%
0%
0%
22%
24%
0%
Total %
VA +
NVAR %
14%
0%
0%
12%
0%
100%
0%
100%
100%
100%
21%
0%
42%
12%
16%
6%
101%
23%
T.W.S.A
77%
5%
13%
1%
NVAR =
9%
Waste
NVAR
Extra
Material
Transport
Movement
In Proc. Ins.
Processing
Pos.
3%
8%
18%
5%
2%
0%
4%
0%
18%
0%
11%
0%
16%
25%
0%
0%
0%
23%
0%
0%
12%
0%
17%
19%
0%
4%
9%
7:57:07 h:m:s
Total %
VA +
NVAR %
8%
38%
0%
3%
2%
100%
100%
100%
100%
100%
39%
56%
68%
60%
51%
3%
99%
40%
T.W.S.A
60%
6%
2%
17%
13%
0%
Cumulative
Number of
Cycle time for each % of Total
Time for
members
element installed
Time
various
observed
categories
Total cumulative Time for two columns
Total Cumulative Time for 2 Girders
Total Time
100%
0%
100%
100%
100%
4%
0%
Area
1
0%
61%
27%
VA +
NVAR %
T.W.S.A
0%
0%
Total %
In Proc. Ins.
1:19:32
2:10:31
7:57:07
11:27:10
2
2
26
0:39:46
1:05:15
0:18:21
12%
19%
69%
Area 3
Figure 6.6: Level Three Data
81
% of Total Time
each steel
element requires
5.8%
9.5%
2.7%
11:27:10 h:m:s
Total %
VA +
NVAR %
19%
38%
0%
5%
2%
100%
100%
100%
100%
100%
43%
56%
57%
42%
42%
9%
100%
46%
T.W.S.A
25%
22%
53%
Area 2
Finally, Area 3 breaks down the proportion of time each substage requires in the main stage. This
distribution is necessary when determining the weighted percentage of total time spent on each
substage in Level Two. From this table, the cycle times can be computed for each building
component erected. For example, the average cycle time to erect a bar joist from the ground into
its final position was calculated by taking the time required to install one element (18 minutes,
21 seconds) and dividing it by the total number of crew members (5). The cycle time for one bar
joist was determined to be three minutes, 40 seconds.
6.9.2 Level Two
Level Two, shown on Figure 6.7, details the substages that occur in one of the main stages of
Level One. Again, this level is necessary when multiple tasks or crews in one process occur at
the same time. The hatched arrows represent the order of occurrence for each substage. The
number of substages shown in Level Two will be dependent on the level of detail that an
observation team makes while collecting data. For example, on Figure 6.7, three distinct
activities are highlighted: column, girder and bar joist erection. However, in a second structural
steel case study, the column and pod/spandrel beam combination (girder section) is represented as
one substage. This simplifies the data analysis, but limits the information that can be obtained if
these two substages (i.e., crew balance information) are separated.
Note: These Steps occur at the same time.
Columns and Girders are erected first but
cannot be continued until the inner
supporting bar joist have been erected.
Stage Two (A) - Bar Joists bundles
are shook out
Level Two
Days Required
2.5
Days Required
Workers involved
Crew
WT
VA ( 0%)
NVAR (0%)
NVA (100%)
2.5
1
Forklifts
2
40
0
0
40
Workers involved
Crew
WT
VA ( 0%)
NVAR (0%)
NVA (0%)
2 Columns Erected per bay
Days Required
Equipment involved:
Equipment involved:
Forklifts
Stage Two (B) - Specific Bar
Joists and girders are pulled
from bundles to be placed in
each bay
2.0
Days Required
Crane, Forklift
2
40
0
0
40
2
Workers involved
Crew
WT=
VA ( 6%) =
NVAR (34%) =
NVA (60%) =
3.2
Equipment involved:
Crane, 2
Skylift, Forklift
Workers involved
Crew
WT=
VA ( 8%) =
NVAR (15%) =
NVA (77%) =
Equipment involved:
1
5
78.7
4.7
26.8
47.2
Bar Joist installed along with xbracing members
Days Required
4
5
129.2
10.3
19.4
99.4
Equipment involved:
Crane, Forklift, 2
Skylifts
Workers involved
Crew
WT=
VA ( 31%) =
NVAR (9%) =
NVA (60%) =
11.8
4
5
472
146
42
283
Figure 6.7: Level Two
Figure 6.8 shows one substage box from the steel erection process. The box is developed into
two main sections. Section 1 lists the substage process requirements: days required, equipment
involved and workers involved. Section 2 details the work distribution categories: work, VA,
NVAR and NVA time.
Section 1
Joist Girder is Erected
Days Required
3.2
Equipment involved:
Crane, 2 Skylift,
Forklift
Workers involved
Crew
WT=
VA ( 8%) =
NVAR (15%) =
NVA (77%) =
4
Section 2
5
129.2
10.3
19.4
99.4
Figure 6.8: Typical Setup for a Substage Box in the Value Stream
82
To further illustrate the calculation process for this level the main stage from Level One must be
introduced, along with its required substages in Level Two (Figure 6.9) and the steps in the
calculation demonstrated.
Stage Three - Steel Erection
Process
Days Required
17.0
Equipment involved:
Forklift, crane,
2 to 4
skylifts
Workers involved
Crew
5
WT=
680
VA ( 7%, 13%)
161
NVAR (28%, 21%)
89
NVA (100%)
430
Columns Erected
Days Required
2.0
Days Required
Equipment involved:
Crane, Forklift
Workers involved
Crew
WT=
VA ( 6%) =
NVAR (34%) =
NVA (60%) =
Bar Joist installed along with xbracing members
3.2
Days Required
Equipment involved:
Crane, 2 Skylift,
Forklift
2
5
78.7
4.7
26.8
47.2
Workers involved
Crew
WT=
VA ( 8%) =
NVAR (15%) =
NVA (77%) =
11.8
Equipment involved:
Crane, Forklift, 2
Skylifts
4
5
129.2
10.3
19.4
99.4
Workers involved
Crew
WT=
VA ( 31%) =
NVAR (9%) =
NVA (60%) =
4
5
472
146
42
283
Figure 6.9: Main Stage from Level One Along with Required Substages from Level Two
6.9.2.1 Step 1. The “days required” value is calculated using the weighted percentage of time
spent on a substage. This number is found in Area 3 of Level Three, “% of total time”
(19 percent). This calculation (Equation 6.1) focuses on the days required for girder installation.
Multiply 19 percent by the total number of days required value (17) found in the main stage of
Level One.
Equation 6.1: 17 days x 19% = 3.23 (cumulative days to erect every girder)
The result is 3.23 days. This value indicates that if the crew focused only on the girder erection
process, it would take them a cumulative time period of 3.23 days to erect every girder. Using
this value, the values found in Section 2 of the substage box can be calculated. The equipment
category shows which resources are used for each substage. These values can be used to aid in
balancing the total equipment on a job with the crew to create the best possible flow in the work
process. To complete Section 1, the total number of workers required for the substage was
entered. If the same crew was used for each substage, then this value would remain the same.
However, if two separate crews were involved with the process, these values may not remain the
same between the substage processes.
83
6.9.2.2 Step 2. Section 2 breaks down the work distribution values for that substage. Work
time (WT) is defined as the total workable man-hours a crew can contribute assuming that they
work five days a week, eight hours a day. The calculation for WT is as follows:
Equation 6.2: WT = 8 hours per (day per crew member) x 5 crewmembers x 3.23 days
= 129.2 total available person-hours for the girder erection process
6.9.2.3 Step 3. This WT value must be used as the basis for the remaining categories of VA,
NVAR and NVA. The percentages shown next to VA, NVAR and NVA were developed from
the Level Three tables.3 For each substage, a table was developed with values for NVA and
NVAR. These values were obtained by totaling the subcategory values that contributed to each
of the main work distribution categories (e.g., NVAR = Mat Pos. Value + In-Process Ins. Value +
TWSA Value = 15 percent for girders). The number of man-hours that were contributed to each
work category can now be calculated.
Equation 6.3: NVAR Time = 15% x 129.2 man-hours = 19.4 man-hours
This step was repeated using the VA and NVA percentages to find their respective values.
6.9.2.4 Step 4. These steps were repeated for each substage until all the categories were
complete. Once completed, the main stage box found on Level One totaled all of the values
found in Section 2 of each substage box, resulting in a weighted final value for each stage in
Level One.
Equation 6.4: WT (Stage Three) = WT Substage 1 + WT Substage 2 +WT Substage 3
WT (Stage Three) = 78.7 + 129.2 + 472
WT (Stage Three) = 680 available man-hours
Levels Two and Three are structured to give the contractor (subcontractor) a detailed view of
material movement while onsite, as well as the crew actions required for the installation/erection
of the material into final position. Levels Two and Three allow the contractor to better control
wastes associated with waiting, transport, extra processing and movement. At the project level,
the contractor can use Levels Two and Three to balance crews and the respective tasks required
from each crew member. A balanced crew allows material and processes to reach their ideal
flow. The main reason for the separation of these levels is to give the contractor the ability to
track material movement on two separate time scales. The time required to design, procure and
deliver material to the jobsite (Level One) can be substantially larger than the time required to
install or erect the material after it is onsite (Levels Two and Three).
6.9.3 Level One
Level One of the new value stream (Figure 6.10) is nearly identical to the conventional method.
The solid black arrows represent information paths. Information arrows depict the “routes”
information must currently travel to allow certain activities to proceed. For example, information
flows from the Project Engineer to the steel manufacturer in the form of a “notice to proceed.”
3
For those stages in which material was offloaded from the truck to the ground, a 20 percent standard value
has been assigned for the NVAR category. This is to accommodate for the NVAR actions of setting up
hoist lines, safety lines or whatever else was required to safely move the material to the ground.
84
The manufacturer then produces the required steel elements and ships them to the jobsite. Once
the steel (or any other material) is onsite, it is tracked in stages until it has been installed or
erected into its final position. Information arrows also show how often communication is made
between each party, as the “As Required” and “Daily” notations signify.
The dark arrows leading from the last stage box “Steel in Place Awaiting Welding” to the
“Production Control” box offer a means to track overproduction and defect wastes.
Overproduction is represented in various forms depending on the hierarchy in the project’s
management team. At the owner level, overproduction results from “over designing” the facility.
At the project level, overproduction results from starting activities before they are required by the
ideal “latest responsible start schedule.”
Defect wastes are also represented in various forms depending on the hierarchy in the project’s
management team. At the owner level, a defect may result from a facility not meeting its
requirements because of underdesign or overdesign. At the project level, a defect can be
quantified by determining the amount of time a follow-up crew is required to fix errors or
unfinished work left by a previous crew.
Using material as the “traceable” element, a stage or process box (as is shown on the bottom row
of Figure 6.10) must be created to represent the material at that point in the process cycle. Stages
occur each time the material is touched onsite, beginning with offloading the material into a laydown yard or staging area. Every time the material is moved or transformed (e.g., two structural
elements are combined on the ground but then left there until the installation stage) prior to the
actual installation process, it must be accounted for by a separate stage box. For the remaining
stages that do not have field data to support the required information, the weighted average values
found in Level Three, Area 2, must be used.
Below the stage boxes is a staggered line with numbers placed between each stage box. These
numbers represent the days of inventory that occur between each stage. The number is based on
each shipment of material to the site. Inventory waste is quantified in Level One by totaling all
inventory days. An inventory day starts when the material is received onsite, and ends when the
last material piece in the shipment is moved to its next staging position or is installed. For
example, if two shipments of steel are delivered to the site, each shipment is treated separately to
identify the element in that shipment that remains on the ground the longest before being moved
to its next stage in the process life cycle. The period of time between each phase gives a portion
of the total inventory waste. The goal of tracking this waste is to reduce the inventory days to the
ideal value of zero. At this point, material flows onto the site, proceeds through all necessary
stages and is installed into its final position without being stored in various completion stages.
Another way to shrink this value is to order smaller batches of material for each delivery. If the
batch size is smaller, the time required to use up all the material in that one batch should decrease.
Therefore, the piece of material remaining longest onsite is governed by the consumption rate of
the crew erecting or installing those elements. In a financial sense, this means that the “front
end” costs of material delivered to the site may not rise as fast as it would with the current
practice of large batch material orders.
Once all stages are complete, the finished process box can be shown. In this example, it is
labeled “Steel in Place Awaiting Welding.” From the finished process box, the information
arrows relate process-specific information such as overall feedback on productivity and percent
complete for billing applications.
85
Production Control
Project Engineer
Every 1-3 days
Triggering Event
Project Feedback
Level One
2 phases of steel are ordered
Percent Complete
Time
Alloc
ation
Field
NVA Time
NVAR Time
1
VA Time
Steel Supplier
Supplie
Daily
As Required
5 cumulative days to deliver steel
O
OO
0
Stage Two (A,B) - Steel Shake
out Process
Days
5
Required
Equipment involved:
2
Equipment involved:
Forklifts
Workers involved
Crew
WT
VA ( 0%)
NVAR (20%)
NVA (80%)
2
Forklifts
2
32
0
6.4
25.6
100
200
300
400
500
600
700
800
Manhours
O
respective Bays
Days Required
Work Time
Inv
2
1
Workers involved
Crew
WT
VA ( 0%)
NVAR (0%)
NVA (100%)
2
80
0
0
80
Inv
8
Figure 6.10: Level One
86
**Graph
**
Graph shows the amount of man-hours atributed to each
work category. VA time + NVAR time + NVA time = Work
Days Required
17.0
Time
Equipment involved:
Forklift, crane,
2 to 4
Summary of all stages in Level 1
skylifts
Workers involved
Working
Wor
king Days
24 days
Woking Time
792man
792 man hours
Crew
5
WT=
680
VA Total
161man
161 man hours
VA ( 7%, 13%)
161
NVA Total
95 man hours
NVAR (28%, 21%)
89
NVAR Total
536man
536 man hours
NVA (100%)
430
Inventory Days
10
Finally, the table to the right of the stages provides a “quick” summary for all of the stages in
Level One. The bar chart above the table represents these values in a graphical display.
In summary, Level One is structured to allow the contractor to directly control waste associated
with overproduction (WIP) and inventory. Pure overproduction is rare on a construction site,
since most construction is built for a specific order. However, any time that a contractor orders
more material than is required during the project for a specific time period, it contributes to overproduction waste. Overproduction also accounts for WIP where an activity is left partially
completed because insufficient materials were available or the activity was started before it was
called for by the construction schedule. A late start schedule is ideal for limiting waste resulting
from WIP. Inventory accounts for instances when the contractor orders more material than is
required to complete the job, thus resulting in excess raw material at the completion of the
project. A well developed value stream map at this level will also indirectly affect how much
waiting occurs between construction activities, amount of transport required for materials around
the jobsite and the proportion of extra processing (rework) required because of defective
materials delivered onsite.
6.10 New Idea for Displaying the Construction Value Stream
Figure 6.11 represents the work distribution life cycle graph for the first case study; it demonstrates how the work distribution values grow throughout the process (steel erection, piping
installation, etc.). The chart’s main goal is to represent how each work category grows as work
progresses through the various stages in Level One. The vertical line marks the point where work
activities change from the delivery and preparation stages to the actual erection stage. There are
five lines shown in the chart: the Cumulative Calendar Hours, Cumulative Workable Hours,
Cumulative VA Hours, Cumulative NVAR Hours, and Cumulative NVA Hours. The data table
for this graph is shown in Table 6.16. Each of the lines is based on an eight hour workday. For
Cumulative Calendar Hours, the available work hours include weekends, where the Cumulative
Workable Hours only account for a five day work week. The remaining Cumulative VA, NVAR
and NVA Hours are calculated using the daily available work hours (shown in Column 11 of
Table 6.16) as the multiplier.
To create Figure 6.11, the following steps must be repeated. The first step is to create the value
stream map. From the results of this map, the stages defined in Level One can be used to create a
schedule of events, as shown in Table 6.16. In the first column of Table 6.16, the individual
stages are defined. Column 2 lists the primary specific activity that is occurring for that day. The
primary activity is determined by which task is absorbing the majority of the crew’s time for that
day. Each row represents another day, moving left to right across the table. Column 3 details
which day the activity occurred. For simplicity, all processes begin on a Monday. Column 4
shows a running total of calendar days the process takes to complete. Column 5 details the
available hours possible for that day. This value is calculated using the total available crew for
the day multiplied by eight hours. These values will be the same for the Column 11, Workable
Hours, except for the rows representing weekends. Calendar hours include possible weekend
hours. To calculate the possible work hours for each day of the weekend, the total available crew
from the Friday before is used, and then the crew size is multiplied eight hours. Column 11
assumes zero workable hours for the weekend; however, this would change should a process
require weekend shifts. The Cumulative Calendar Hours, Column 6, is a running total of all
available calendar hours. The logic is similar for the Cumulative Workable Hours, Column 12,
except that it is a running total of workable hours.
87
Work Distribution
1200
1000
800
Time (man hours)
Cumulative Calendar Hours
Cumulative Work Hours
600
400
Cumulative VA Hours
Delivery and
Preparation
Process
Erection Process is
underway
Cumulative NVAR Hrs.
Cumulative NVA Hrs
200
Note: the percentages used to
create this chart are the
average values from the work
distribution values found for the entire crew.
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
Calendar Days
Figure 6.11: Work Distribution Life Cycle Graph
88
Table 6.16: Work Distribution Lifecycle Data
Stage
Stage 1
Stage 1
Stage 2
Stage 2
Stage 2
Weekend
Weekend
Stage 2
Stage 2
Stage 3
Stage 3
Stage 3
Weekend
Weekend
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Weekend
Weekend
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Weekend
Weekend
Stage 3
Stage 3
Stage 3
Stage 3
Primary Activity for the Day
Steel is moved from truck to ground
Steel is shook out
Steel is shook out
Steel is shook out
Weekend
Weekend
Steel is shook out
Steel is shook out
1 crew erecting S.S. (Columns, Joist Girder and Bar Joists)
Weekend
Weekend
Weekend
Weekend
Weekend
Weekend
Day
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Monday
Tuesday
Wednesday
Thursday
Cumulative
Cumulative
Hours
Calendar Calendar
Workable
Crew
Workable Cumulative VA
NVAR
NVA VA Cumulative NVAR Cumulative NVA Cumulative
Calendar
Workable
worked
Days Hours
Days
available
Hours Work Hours Percentage Percentage Percentage Hours VA Hours Hours NVAR Hrs. Hours NVA Hrs
Hours
days
per day
1
16
16
1
1
2
8
16
16
0%
20%
80%
0
0
3.2
3.2
12.8 12.8
2
16
32
1
2
2
8
16
32
0%
20%
80%
0
0
3.2
6.4
12.8 25.6
3
16
48
1
3
2
8
16
48
0%
0%
100% 0
0
0
6.4
16
41.6
4
16
64
1
4
2
8
16
64
0%
0%
100% 0
0
0
6.4
16
57.6
5
16
80
1
5
2
8
16
80
0%
0%
100% 0
0
0
6.4
16
73.6
6
16
96
0
5
2
0
0
80
0%
0%
100% 0
0
0
6.4
0
73.6
7
16
112
0
5
2
0
0
80
0%
0%
100% 0
0
0
6.4
0
73.6
8
16
128
1
6
2
8
16
96
0%
0%
100% 0
0
0
6.4
16
89.6
9
16
144
1
7
2
8
16
112
0%
0%
100% 0
0
0
6.4
16 105.6
10
40
184
1
8
5
8
40
152
25%
22%
53% 10
10
8.8
15.2 21.2 126.8
11
40
224
1
9
5
8
40
192
25%
22%
53% 10
20
8.8
24
21.2 148
12
40
264
1
10
5
8
40
232
25%
22%
53% 10
30
8.8
32.8 21.2 169.2
13
40
304
0
10
5
0
0
232
25%
22%
53%
0
30
0
32.8
0
169.2
14
40
344
0
10
5
0
0
232
25%
22%
53%
0
30
0
32.8
0
169.2
15
40
384
1
11
5
8
40
272
25%
22%
53% 10
40
8.8
41.6 21.2 190.4
16
40
424
1
12
5
8
40
312
25%
22%
53% 10
50
8.8
50.4 21.2 211.6
17
40
464
1
13
5
8
40
352
25%
22%
53% 10
60
8.8
59.2 21.2 232.8
18
40
504
1
14
5
8
40
392
25%
22%
53% 10
70
8.8
68
21.2 254
19
40
544
1
15
5
8
40
432
25%
22%
53% 10
80
8.8
76.8 21.2 275.2
20
40
584
0
15
5
0
0
432
25%
22%
53%
0
80
0
76.8
0
275.2
21
40
624
0
15
5
0
0
432
25%
22%
53%
0
80
0
76.8
0
275.2
22
40
664
1
16
5
8
40
472
25%
22%
53% 10
90
8.8
85.6 21.2 296.4
23
40
704
1
17
5
8
40
512
25%
22%
53% 10
100
8.8
94.4 21.2 317.6
24
40
744
1
18
5
8
40
552
25%
22%
53% 10
110
8.8
103.2 21.2 338.8
25
40
784
1
19
5
8
40
592
25%
22%
53% 10
120
8.8
112 21.2 360
26
40
824
1
20
5
8
40
632
25%
22%
53% 10
130
8.8
120.8 21.2 381.2
27
40
864
0
20
5
0
0
632
25%
22%
53%
0
130
0
120.8
0
381.2
28
40
904
0
20
5
0
0
632
25%
22%
53%
0
130
0
120.8
0
381.2
29
40
944
1
21
5
8
40
672
25%
22%
53% 10
140
8.8
129.6 21.2 402.4
30
40
984
1
22
5
8
40
712
25%
22%
53% 10
150
8.8
138.4 21.2 423.6
31
40
1024
1
23
5
8
40
752
25%
22%
53% 10
160
8.8
147.2 21.2 444.8
32
40
1064
1
24
5
8
40
792
25%
22%
53% 10
170
8.8
156 21.2 466
89
Column 7, Workable Days, provides a base for the remaining calculations. If a 1 is shown in
Column 7, then the row represents an actual workday; if the value is 0, then it represents a nonworking day (i.e., a weekend or a holiday). Column 8, Cumulative Workable Days is a running
total of possible workdays. The columns representing percentage values for VA, NVAR and
NVA obtain their values from the stage boxes in Level One of the value stream map.
6.11 How Do the Value Stream Maps Differ Between Processes?
For both steel and piping processes, the same steps are required to develop a value stream map.
The main difference between the structural steel value stream map and that of the piping process
is that the steel production process requires several substages. The substages occur simultaneously in a “family” of processes to complete the entire erection cycle. In general, the steel
production process represents the multiple inputs coming together to produce the single output of
a completed structure. Multiple substages in Level Two of the value stream map are not evident
for the piping production process because of the nonrepetitive elements being installed and the
amount of time required to install each piping component. Structural steel elements typically
consist of columns, girders and bar joists (trusses).
90
7.0 Results - Lean Principles for Construction
7.1 Assessing Lean Principles for Construction
In this chapter, the findings from the literature, the interviews and the case studies are synthesized
into a comprehensive assessment of the applicability of lean principles to the construction
process. The following analysis is organized by major principle and then subprinciple. Each
subprinciple was evaluated for its applicability to the construction industry and given a rating of
0, 25, 50, 75 or 100 percent. A principle that is clearly applicable to the construction industry
(i.e., 100 percent) will be denoted with the following graphic:
100%
In addition, an assessment was made regarding applicability of the principle by industry role; that
is, whether it applies to the owner, contractor, subcontractor, designer or supplier. The roles of
both designers and the material suppliers have been evaluated, although supply chain and design
issues were excluded from the study. Accordingly, the judgments about designer and supplier
roles are not based on the same degree of evidence as are the judgments about the roles of
contractors and subcontractors. These judgments are represented as bar charts, as follows:
Meeting Requirements of the Customer
100%
80%
60%
40%
20%
0%
50%
20%
10%
10%
G
EN
H
C
(A
R
D
es
ig
ne
r
Su
pp
li e
rs
or
ra
ct
Su
bc
on
t
on
tra
ct
or
C
O
w
ne
r
)
10%
Finally, each subprinciple was evaluated for applicability at all three levels of the organization;
namely, crew, project management and enterprise. This evaluation is both an assessment of the
level at which the principle is best applied and an appraisal of the organization level that has the
primary responsibility for implementing the given principle. This judgment is represented as
follows:
100%
100%
100%
80%
80%
60%
40%
20%
0%
Enterprise Level
Project Level
91
Crew Level
Subprinciple No. 1.1: Meet the Requirements of the
Customer. Customer focus is a key principle for lean construction.
However, implementation of this principle differs significantly from
implementation in other industries because of the intimate relationship
between the customer (owner) and contractor in construction.
Ironically, customer focus is a lean behavior of both the owner and the
contracting team. Construction team focus on customer value must be
a culture that is adhered to at the workface, at the project level and at the enterprise level.
However, in construction, the contractor must also advise the customer about the appropriateness
of his/her definition of value. The contractor may help the customer develop a better definition of
value; i.e., defining what the customer needs, not what the customer wants.
100%
Customer focus in construction is more intimate than in manufacturing; it is more dependent on
the needs and behaviors of a specific customer. Manufacturing is like speculative building in
construction. In speculative building, one tries to build the most desirable house for the least
money, targeting a particular market demographic. In custom construction, customer focus is
more of a give-and-take process; the customer can be asked to change its idea of value for the
good of the project; e.g., if a design standard is changed, the project will save money and time.
Customer focus is a matter of culture. “Lean” customer focus requires a culture different from
“normal” construction culture. Lean customer focus is quite different from adherence to the
principles of the contract. It is about an exchange of values, but not as currently defined by
contract law, and it has little to do with the commercial terms of the contract. It has everything to
do with the concept that if the customer receives value, both from the product and the process of
construction, the customer will seek return business. The customer must be part of the value
generation process. The customer must understand the importance of certain aspects of value.
This is very different from the current value calculus for manufacturing. In fact, the singular
customer-centric definition of value that is used in custom construction is an aspiration of the
manufacturing sector; e.g., cars built exclusively to order.
100%
100%
100%
100%
80%
80%
80%
50%
60%
60%
40%
20%
10%
20%
10%
10%
40%
0%
r
s ig
ne
rs
De
pp
Su
tr a
0%
bc
on
li e
or
ct
ct
ra
nt
Enterprise Level
Su
Co
O
wn
er
or
20%
Project Level
Crew Level
Therefore, meeting the requirements of the customer is a principle that must be followed by both
the contractor and the owner. It must be part of the culture of the contracting company at both the
enterprise level and the project management level. Meeting the requirements of the customer is
92
also applicable at the worksite/crew level; however, the involvement at this level is more limited
than it is at the higher levels.
Subprinciple No. 1.2:
Define Value from the
Viewpoint of the Customer (Project). Perhaps this is the
essence of lean: the unrelenting focus on delivering value to the
100%
customer. However, for many companies involved in construction,
there is a genuine problem of identifying the customer. From the
point of view of the subcontractor on a commercial building
project: is the customer the general contractor, the developer or the
ultimate owner of the building? This ambiguity is the source of a considerable amount of
suboptimization in the construction process. It is the challenge of the lean contractor to organize
the delivery process in such a way that the intermediate views of value are reconciled with the
customer’s view of value.
Value Adding Is Defined from the View of the
Project
Value Adding Is Defined from the View of the
Project
100%
100%
100%
100%
100%
100%
100%
100%
80%
80%
80%
60%
60%
40%
20%
0%
40%
r
s ig
ne
rs
0%
De
pp
Su
ct
tr a
20%
bc
on
li e
or
or
ct
ra
nt
Enterprise Level
Su
Co
O
wn
er
0%
Project Level
Crew Level
Defining value from the point of view of the ultimate customer is applicable to all major groups
(contractor, subcontractor, designer and supplier) in construction. Likewise, every level in the
project organization must be prepared to add value for the customer. The contractor must take
the lead in establishing the value structure both for its own organization and for all of the other
subordinate organizations involved with the project.
Subprinciple No. 1.3: Use Flexible Resources and
Adaptive Planning. Manufacturers employ many devices
to allow them to respond to changing market conditions. Pull
production schedules and flexible manufacturing systems are
just two methods. Construction companies must also be able to
respond rapidly to changing owner needs and marketplace
conditions. It is common for changes in the market to cause
industrial owners to change product mixes. Likewise, it is common for belatedly identified
requirements to cause changes in project design. To define value from the customer’s viewpoint,
the lean contractor must be able to respond to these changing needs by employing flexible
resources and adaptive planning systems. However, contract arrangements between multiple
project participants often inhibit the contractor’s ability to quickly change the scope or schedule
of a project. Implied by this need for flexibility must be an understanding by the owner that
flexibility comes at the price of disrupting established systems and standardized processes.
100%
93
Flexible Resources and Adaptive Planning
100%
100%
100%
Flexible Resources and Adaptive Planning
100%
100%
100%
100%
Enterprise Level
Project Level
Crew Level
100%
100%
80%
80%
60%
60%
40%
40%
20%
0%
0%
r
ne
rs
Su
De
pp
s ig
li e
or
ct
tr a
0%
Su
Co
bc
on
nt
O
ra
wn
ct
er
or
20%
Flexible and responsive systems must be developed at every level in the project and by every
member of the project team. The need for flexibility is a natural outgrowth of defining value
from the customer’s viewpoint.
Subprinciple No. 1.4: Cross Train Crew Members
to Provide Production Flexibility. Manufacturing
industries use cross training to provide work floor flexibility and
to provide job enrichment. Cross training is already used in
some open shop sectors of construction. Cross training to
provide flexibility is more difficult in a union environment.
However, cross training within a crew is very useful for
improving the production management aspects of construction operations. One of the most
vexing problems in construction production system design is sizing a crew to perform multiple
operations (installing columns, girders and joists). Cross training can enable planners to
distribute work and balance crews.
100%
Cross Trained Crew Members
Cross Trained Crew Members
100%
100%
100%
100%
100%
80%
80%
60%
60%
40%
20%
10%
0%
10%
50%
40%
r
ne
rs
s ig
0%
De
pp
Su
tr a
20%
0%
Enterprise Level
Su
bc
on
li e
or
ct
ct
ra
nt
Co
O
wn
er
or
0%
Project Level
Crew Level
Cross training is applicable for both contractors and subcontractors. The field staff must take
primary responsibility for cross training to the extent that it is permitted by labor agreements.
Both designers and suppliers may have minor opportunities to help allow for cross training by
understanding jurisdictional boundaries in union labor agreements.
94
Subprinciple No. 1.5: Use Target Costing and
Value Engineering. Manufacturers use target costing as a
device to focus their cost reduction efforts. In manufacturing,
Toyota made famous the idea that “Profit = Market Price Costs.” That is, the market determines the price, and profit can
only be increased by reducing costs. This idea is similar to the
competitive bidding culture prevalent in construction. In fact,
construction’s intense reliance on low-bid pricing shifts the focus away from customer quality to
price. The lean contractor can rely on target costs as a device for reducing costs but not to the
disadvantage of quality. Value engineering is the method commonly used in construction both to
reduce costs and to maintain quality and functionality.
100%
Target Costs - Value Engineering
Target Costs - Value Engineering
100%
100%
100%
100%
100%
100%
100%
100%
80%
80%
60%
60%
40%
20%
50%
40%
0%
O
wn
er
Co
n
tr a
ct
or
S
c
ub
on
c
tr a
to
r
Su
li
pp
s
er
D
ig
es
ne
20%
r
0%
0%
Enterprise Level
Project Level
Crew Level
Target costing (appropriately applied) and value engineering can be practiced by every member
of the project team. The main responsibility lies with the enterprise level.
Subprinciple No. 2.1: Provide Training at Every
Level. The need for training in developing a lean organization
and a lean culture is undisputed. Lean thinking requires
modification of long-standing ideas about every aspect of the
construction process. All of the “lean” companies encountered
in the study emphasized the need for training. Some lean
contractors also train their suppliers, subcontractors and craftspersons.
100%
Training
100%
Training
100%
100%
100%
100%
100%
100%
100%
Enterprise Level
Project Level
Crew Level
100%
75%
80%
80%
60%
60%
40%
20%
40%
r
De
s ig
ne
rs
pp
Su
tr a
20%
0%
Su
bc
on
li e
or
ct
ct
ra
nt
Co
O
wn
er
or
0%
95
All parties to the process must support the central role of training for implementing lean
principles. Even owners must participate in training so that they understand the potential of lean
construction.
Encourage Employee
Empowerment. One of the most difficult challenges of
becoming lean is the task of empowering employees at every
level.
Empowerment is important for implementing
improvements and suggestion programs and for having all
workers feel personal responsibility for process improvement
and quality. Employee empowerment in manufacturing found
its most profound application in the idea that any employee could “stop the line” if he or she
noticed a quality problem. The transient nature of the construction workforce and the temporary
nature of the construction team make employee empowerment difficult.
100%
Employee Empowerment
100%
100%
100%
100%
100%
100%
100%
80%
80%
60%
40%
25%
20%
60%
25%
0%
40%
r
De
s ig
ne
rs
pp
Su
ct
tr a
20%
0%
Su
bc
on
li e
or
or
ct
ra
nt
Co
O
wn
er
0%
Enterprise Level
Project Level
Crew Level
Owners, designers and suppliers have little involvement in employee empowerment. Contractors
and subcontractors, on the other hand, must institute programs that motivate employees to take
responsibility for quality and process improvement. Some lean contractors use “gain sharing” as
a device to engage the construction workforce in process improvement. All levels of the
organization have significant accountability for ensuring that employees feel empowered to act to
improve project outcomes.
Subprinciple No. 2.3: Ensure Management Commitment. Creating a lean culture is perhaps the best precursor
of superior lean performance. Management commitment to the
lean ideal is fundamental to lean culture. Lean behavior that is
an everyday work ethic of managers, employees and strategic
partners is best ensured by unrelenting commitment to lean
ideals. Toyota has been working on developing the Toyota
Production System for decades. Lean construction will require a commitment of similar duration.
Several lean contractors reported that they have stayed committed to lean principles even though
they have not realized improved profits. Rather, many have cited the need for continued
application and extensions of lean concepts beyond those already adopted to realize the full
promise of a lean system. In the absence of improved profits, many lean contractors cite benefits
other than improved profits, such as improved quality and better employee morale.
100%
96
Management Commitment
100%
100%
100%
100%
100%
100%
100%
100%
100%
Enterprise Level
Project Level
Crew Level
100%
80%
80%
60%
40%
60%
20%
40%
r
ne
rs
Su
De
pp
s ig
li e
or
tr a
20%
0%
Su
bc
Co
on
nt
O
ra
ct
ct
wn
or
er
0%
Owner, contractor and subcontractors must all embrace the lean ideal for a long period of time.
The use of strategic partnerships between contractor and subcontractor make it easier to sustain
lean behaviors from job to job. All levels of management from the CEO down to the first-line
crew supervisor must be committed to lean practices.
Subprinciple No. 2.4: Work with Subcontractors
and Suppliers. Much of the benefit of lean systems derives
from the partnerships that develop between supplier and
manufacturer. However, in construction, it is difficult to
develop long-term relationships between contractor and
subcontractor or contractor and supplier because of the location
variability customary to construction production. Another
problem not generally experienced by the lean manufacturer is the lack of control that contractors
have over their supply chain. A large manufacturer (e.g., Toyota, Ford) buys such a large
quantity of goods (e.g., tires or windshields) that it has significant influence on the terms of the
transaction. In contrast, any single contractor represents only a small fraction of any supplier’s
sales; therefore, the contractor has less influence over the supplier. Also, the materials that must
be procured are typically specified by the design, and the contractor often has no opportunity to
work with a preferred supplier. Thus, the form of project delivery system (design-build, designbid-build) has an impact on possible supplier-contractor relationships. Despite all of these
obstacles, it is very important that suppliers and contractors/subcontractors understand and
maintain lean behavior in construction. Long-standing relationships between suppliers and
subcontractors will facilitate adoption of lean ideas. Developing long-standing relationships will
require basic changes in construction routines.
100%
Subcontractor and Supplier Interactions
100%
100%
Subcontractor and Supplier Interactions
100%
100%
100%
100%
100%
80%
75%
80%
60%
40%
60%
25%
20%
0%
40%
r
De
s ig
ne
rs
pp
Su
ct
tr a
20%
0%
bc
on
li e
or
or
ct
ra
nt
Enterprise Level
Su
Co
O
wn
er
0%
97
Project Level
Crew Level
Owners have little involvement in maintaining the contractor/subcontractor or contractor/supplier
relationship other than to provide a delivery system that enables these relationships. Clearly, the
main responsibility for establishing and maintaining strategic relationships is with the contractor.
Contractor personnel at every level have a role to play in maintaining effective working
relationships with suppliers and subcontractors.
7.1.3 Workplace Organization/Standardization
Subprinciple No. 3.1: Encourage Workplace Organization and Use 5S’s. The main imperative of manufacturing
production is to eliminate waste. One technique manufacturers use is
to make it obvious when something is wrong with the tools, materials
or processes of production. One method that manufacturers use is to
make everyday aspects of the process routine: tools and materials are
organized in the same way, work areas are kept neat and clean. This is
a more difficult undertaking in construction because the “factory” is always changing
configuration. However, strict adherence to a policy that requires cleanliness, organization and
orderly storage and movement plans is a necessary step toward lean production. Gang boxes,
tools and consumable supplies should be stocked and organized so that no time is spent searching
for or retrieving common tools or materials. Some lean contractors develop and distribute weekly
plans that detail traffic, lay-down and work area assignments.
100%
5s's
100%
5s's
100%
100%
100%
100%
80%
80%
60%
60%
20%
0%
0%
0%
40%
r
40%
20%
50%
ne
rs
s ig
De
pp
Su
tr a
0%
0%
bc
on
li e
or
ct
ct
ra
nt
Enterprise Level
Su
Co
O
wn
er
or
0%
Project Level
Crew Level
Jobsite cleanliness, organization and logistics are the primary responsibility of the contractor and
the subcontractors. Field management must set the requirement for jobsite organization, but it
must be implemented by the work crews and first-line supervisors.
Subprinciple No. 3.2: Implement Error-Proofing
Devices.
Error-proofing (poke yoke) devices are
commonplace in manufacturing. The simplest manufacturing
operations are guided by jigs and fixtures. Error-proofing is
another way that manufacturing firms standardize the production
process. Error-proofing devices lessen the demands on the
work, improve throughput and enhance quality. Error-proofing
devices are used to a small extent in construction (directional piece marks, welding fixtures, etc.);
however, much more could be done. Principally, error proofing is the responsibility of the
individual worker and post-construction quality inspections. The attitude in manufacturing is to
100%
98
“build quality in”; the attitude in construction is often to “inspect quality in.” The significant
attribute that enables error proofing is repetition. Repetition allows the production process to
move toward production work and away from craftwork.
Poke Yoke Devices
Poke Yoke Devices
100%
100%
100%
100%
100%
100%
100%
80%
80%
60%
60%
40%
20%
50%
40%
0%
0%
r
ne
rs
Su
De
pp
s ig
li e
or
ct
tr a
0%
0%
Enterprise Level
Su
Co
bc
on
nt
O
ra
wn
ct
er
or
20%
Project Level
Crew Level
The responsibility for error proofing rests with all contributors to the construction production
process. Designers have opportunities to use standard design elements and features that allow
error proofing. Suppliers can be alert for opportunities to mark or modify products to facilitate
error proofing. Contractors and subcontractors alike can standardize processes.
Subprinciple No. 3.3: Provide Visual Management Devices. Visual management is the practice of using
graphical and visual devices to help manage and make routine
the production processes.
Visual management tools in
manufacturing cover an array of applications from production
control through quality control. Some lean contractors use
visual management devices to relate cost, quality and schedule
status. Others use visual devices to regulate traffic, lay-down and work zone assignments. Visual
management devices are another means to reduce the load on the workforce and communicate
goals and production metrics.
100%
Visual Management
Visual Management
100%
100%
100%
100%
100%
100%
80%
80%
60%
60%
40%
20%
0%
0%
50%
40%
0%
0%
r
De
s ig
ne
rs
pp
Su
ct
tr a
0%
bc
on
li e
or
or
ct
ra
nt
Enterprise Level
Su
Co
O
wn
er
20%
Project Level
Crew Level
Visual management is the prime responsibility of field personnel. Both the contractor and
subcontractor can employ visual management tools. The impetus for visual management comes
99
from the enterprise level in the organization; the implementation is the responsibility of the
project site management and first-line supervisors.
Create Defined Work
Processes. Defined work processes are the essence of
manufacturing methods. Much of the production planning and
scheduling that is needed to produce a manufactured item is
determined by the production line. Work tasks occur in a
defined sequence, with fixed timing and with standardized
techniques. Manufacturers have the advantage of recouping the
cost of developing defined work processes from the sale of thousands of product items.
Construction is not as fortunate; only in residential building are there multiple replications of the
same project. However, most individual work processes in construction are subject to repetition.
Common work processes (erecting steel, fabricating formwork, prefabricating pipe spools) will
benefit from standard work practices, tools and techniques. Construction has a heritage of craft
work. Typically, work methods and tools are the province of individual workers and work crews.
Manufacturing employs production engineers to define work processes and required equipment.
Lean contractors will need to move toward a more rigorous definition of common work tasks.
100%
Defined Work Processes
100%
Defined Work Process
100%
100%
100%
Project Level
Crew Level
100%
100%
80%
80%
60%
40%
25%
20%
60%
25%
50%
40%
0%
r
De
s ig
ne
rs
pp
Su
tr a
20%
0%
Enterprise Level
Su
bc
on
li e
or
ct
ct
ra
nt
Co
O
wn
er
or
0%
As with most construction production principles, the foremost responsibility for creating standard
work processes rests with the contractor and subcontractor. Material suppliers and designers have
the prospect of enabling defined work processes through more standardization in design and
materials. Development of standard work processes occurs in the field with field management
and the crew. The enterprise level has the responsibility for ensuring that the standards are
applied across all projects. Reapplication of standardized processes will allow for the
amortization of the cost of development of lean work processes.
Subprinciple No. 3.5: Create Logistic, Material
Movement and Storage Plans.
Manufacturing
production is defined by the configuration of the factory plant
and equipment. When a lean contractor defines storage,
movement and logistics plans, a temporary but standard
production infrastructure is created. As with most production
standardization techniques, it is relatively costly to maintain and
communicate standardized site logistics. However, as the value stream studies show, excessive
time is spent in construction moving, shifting and double handling materials. The lean contractor
100%
100
believes that time and money spent in organizing the worksite and creating production
infrastructure is repaid by reducing waste in direct production activities.
Logistics Material Movement Plan
100%
Logistics Material Movement Plan
100%
100%
100%
100%
80%
80%
60%
40%
60%
25%
20%
0%
40%
0%
r
De
s ig
ne
rs
pp
Su
tr a
25%
20%
0%
Enterprise Level
Su
bc
on
li e
or
ct
ct
ra
nt
Co
O
wn
er
or
0%
50%
Project Level
Crew Level
The main responsibility for creating logistics and material movement plans rests at the jobsite.
Both the contractor and subcontractors can contribute, but it is the prime contractor that has
overall responsibility for creating the plans. Prime contractors and subcontractors share
implementation responsibilities. The executive level of the company is responsible for
disseminating the practice across all projects. Site management creates and implements the
principle, and site workers must follow the plan.
7.1.4 Waste Elimination (Aspect 1: Process Optimization)
Subprinciple No. 4.1: Minimize Double Handling
and Worker and Equipment Movement.
Both
construction and manufacturing operations handle large
quantities of material frequently. In a manufacturing environment, material handling operations are predictable and governed
by the configuration and speed of the assembly line. In
construction, material handling requirements are much more
variable. Not only must workers and machines move variously sized and different numbers of
items, they must also move them to diverse locations with variable frequency. Thus, the lean
construction company must spend more time organizing and planning logistical efforts.
Maximum use of Ready for Installation (RFI) tags and bar codes can aid this process. One lean
contractor’s efforts to arrange for steel deliveries in order of erection were stymied when multiple
steel fabrication companies were employed (e.g., one firm for columns and girders, another for
bar joists).
100%
Part of the challenge is to coordinate the material handling and storage needs among the various
subcontractors. Individual subcontractors attempt to reduce delays by ordering and storing large
quantities of materials near their workplaces (i.e., just-in-case material delivery). However, it is
evident that the more materials stored by subcontractors, the higher the incidence of multiple
handling of stored materials to eliminate space conflicts. This illustrates an important point: for
lean construction to be successful, contractors must find ways to eliminate subcontractors’
attempts to optimize their individual goals (profit, productivity, production) at the expense of the
whole production system. Lean is by its nature an optimization of the whole system.
101
To eliminate storage conflicts, one can closely control access to work locations, require
intermediate storage in remote locations or use just-in-time (JIT) delivery of material.
Controlling and scheduling subcontractor access to work areas tends toward a batch and queue
approach to scheduling. Reducing material storage conflicts at the worksite by requiring
intermediate remote storage causes double (or triple) handling, which is by definition a form of
waste. Relying on JIT deliveries, given the activities of a construction site, is (in the current
climate) very risky. The research for this study found no perfect (i.e., similar to manufacturing
performance) solution for storage conflicts in construction. The best solution appears to be a
tightly defined batch and queue management of work locations, coupled with small batch (almost
JIT) deliveries of material.
Minimized Double Handling
Minimized Double Handling
100%
100%
100%
100%
100%
80%
80%
60%
60%
40%
20%
0%
0%
50%
40%
0%
0%
r
ne
s ig
De
li e
rs
pp
r
0%
0%
Enterprise Level
Su
bc
on
Su
c to
tr a
ac
n tr
Co
Ow
ne
to r
r
20%
Project Level
Crew Level
Just because it is difficult to achieve manufacturing style material handling performance does not
mean that construction cannot benefit from attention to material handling performance. During
the value stream studies, multiple incidences were observed where coordination with suppliers or
preplanning for staging materials would have significantly reduced double handling. Contractors
and subcontractors must expend more effort in planning and managing the material handling
aspects of the production system if they are to improve lean performance. The responsibility for
these actions rests with field management and the individual crews.
Subprinciple No. 4.2: Balance Crews, Synchronize
Flows. The flow principle, as described in Chapter 2, is central to
lean production. Flow permits high throughput and fast cycle times.
In a (relatively) steady-state manufacturing environment, it is easier
75%
to establish balanced operations than it is in construction. In
construction, flow is viewed at several levels. First, there is flow
within a crew. Crews often perform different tasks (e.g., erect columns, erect girders, erect
joists); it is difficult to internally balance the crew so that it is “right-sized” for each individual
task. Second, there is flow between crews. In value stream Case Study No. 3, crews were
organized to synchronously follow one another; the first erected columns and beams, the second
the joists. It is possible to maintain synchronous flow between crews on repetitive projects (highrise buildings, multi-unit housing). However, it is very difficult to maintain tight coupling
between crews when work tasks are variable (e.g., process piping). Loose coupling between
crews can be achieved by creating buffers between consecutive crews; however, buffers are
discouraged in “pure” lean production schemes. Third, there is flow among subcontractors,
which is very much like flow between crews with the added complication of contractual
102
scheduling commitments. All flow/crew balancing tasks are made easier if the individual work
task times are reliable. Reliable flow is also facilitated through production/look-ahead planning.
Synchronize Flow
100%
Synchronize Flow
100%
100%
100%
100%
80%
75%
80%
60%
60%
40%
20%
0%
0%
40%
0%
0%
r
ne
li e
rs
s ig
Su
De
pp
r
c to
tr a
0%
0%
bc
Co
on
n tr
Ow
ac
ne
to r
r
20%
Su
Enterprise Level
Project Level
Crew Level
Creating flow and synchronized operations is clearly a field responsibility. However, production
planners cannot rely on the configuration of the assembly line to determine sequence. Also,
production planners must adapt flow to the changing configuration of the product itself.
Therefore, communication of production goals and responsibility is mostly maintained through
strict production planning between contractor and subcontractor and between individual crews.
Remove Material
Constraints, Use Kitting, Reduce Input Variation.
Kitting is a technique that is common in construction, especially
in the process industries. It has no precise analogue in
manufacturing, but it has its roots in manufacturing planning.
Removing material constraints is important for reducing waste
(i.e., waiting time) for individual crews. In tightly coupled
production sequences, material constraints for an upstream crew ripple downstream to succeeding
crews. Kitting can be accomplished either by the contractor’s own forces assigned to support
crews or in conjunction with material suppliers. Kitting for a task may encompass materials,
consumables, design data, equipment and even space.
100%
Kitting, Material Constraints, and Minimizing
Input Variation
100%
Kitting, Material Constraints, and Minimizing
Input Variation
100%
100%
100%
100%
80%
80%
60%
40%
60%
25%
20%
0%
0%
50%
40%
0%
r
ne
s ig
De
li e
rs
Su
0%
0%
bc
on
pp
r
c to
tr a
ac
n tr
Enterprise Level
Su
Co
Ow
ne
to r
r
20%
103
Project Level
Crew Level
Kitting is primarily a field activity carried out by project management personnel working with
suppliers. In some jurisdictions, kitting is accomplished by dedicated crews established to
support production work.
Reduce Difficult Setup/
Changeover. Single Minute Exchange of Dies (SMED) is a
manufacturing technique that focuses on quickly modifying the
production facility for manufacturing different products. By allowing fast changeover between alternative products, manufacturers can
produce products in smaller quantity runs without concern for long
plant changeover-related downtime. Changeover from one task to
the next is routine in construction; it takes the form of moving from work location to work
location and from one task to another.
50%
Reduce Difficult Ssetup/Changeover
Reduce Difficult Setup/Changeover
100%
100%
100%
100%
100%
80%
80%
60%
60%
40%
20%
0%
0%
50%
40%
0%
0%
r
s ig
ne
rs
De
pp
Su
ct
tr a
0%
0%
Enterprise Level
Project Level
Crew Level
Su
bc
on
li e
or
or
ct
ra
nt
Co
O
wn
er
20%
Minimizing changeover is a field production planning task. The need for changeover can be
reduced by producing larger batches of one product before switching to the next (e.g., erecting
multiple bays of steel before returning to erect the bar joists). Using larger batch sizes increases
work in progress (WIP), however, which is contrary to lean practices.
Subprinciple No. 4.5: Reduce Scrap. Scrap reduction
is a principle that is commonly used in construction.
Contractors historically have managed formwork, concrete and
100%
other scrap producing activities. Repetitive tasks offer increased
savings from scrap reduction. One lean contractor reduced
piping purchases by 5 percent by ordering exact lengths for
repetitive floor-to-floor runs in a high-rise project. Aggressively
managing scrap requires confidence in design data and tolerance control, because some
construction material waste is caused by allowances for out-of-tolerance construction and design
inaccuracy. Many supply firms are instituting innovative site warehousing programs that
inevitably reduce waste by reducing overstock and restocking charges.
104
Reduce Scrap
Reduce Scrap
100%
100%
100%
100%
Project Level
Crew Level
100%
100%
75%
80%
80%
50%
60%
60%
40%
20%
40%
0%
r
ne
rs
Su
De
pp
s ig
li e
or
ct
tr a
25%
20%
0%
Enterprise Level
Su
Co
bc
on
nt
O
ra
wn
ct
er
or
0%
Scrap reduction efforts require cooperation between contractor, subcontractor, material supplier
and designer. Planning for scrap reduction occurs at the enterprise and project level. Proactive
management of materials is the responsibility of the crews and field management staff.
Use Total Productive
Maintenance. Total productive maintenance (TPM) is a
manufacturing technique for using “off-shift” labor to
proactively maintain production machinery and infrastructure.
Construction normally uses TPM to maintain large equipment
during downtimes or at “off-shift” times. Unplanned equipment
downtime can idle an entire crew. During one of the site visits,
a crane operator was discharged for failing to fuel the crane before starting work. His failure to
fuel the machine caused the entire crew and several other pieces of construction equipment to
experience nonproductive time. This is another example where minor, standardized practices can
lead to large production system improvements.
100%
Total Productive Maintenance
100%
100%
100%
100%
Project Level
Crew Level
100%
100%
80%
80%
60%
60%
20%
0%
0%
0%
40%
r
40%
20%
ne
rs
s ig
De
pp
Su
tr a
0%
0%
Enterprise Level
Su
bc
on
li e
or
ct
ct
ra
nt
Co
O
wn
er
or
0%
TPM activities are administered by the field staff. All field personnel have opportunities to
organize rational maintenance activities for site tools and equipment.
105
7.1.5 Waste Elimination (Aspect 2: Supply Chain)
Subprinciple No. 4.7: Institute Just in Time (JIT)
Delivery. JIT delivery of materials in manufacturing is a well
developed practice. In large-scale manufacturing (e.g., automobiles)
major suppliers co-locate fabrication facilities with the main
75%
production plant to allow rapid response to production needs. JIT in
manufacturing relies on the relative steady-state nature of
production. Construction production is not (generally) steady-state; therefore, more planning is
required to establish JIT delivery of most construction materials. Despite the difficulty of
instituting JIT, it would have a number of benefits for the construction industry. Later delivery of
materials would reduce the carrying costs for the contractor or owner; site congestion; the need
for double handling; and the opportunity for theft, damage or loss. However, JIT presupposes a
close working relationship with suppliers, which is a more difficult problem in construction than
it is in manufacturing because of the relatively smaller scale of individual contractor purchases.
Also, contractors move about the country (and world), and often preferred suppliers are too
distant to be used economically. There is also the issue of incompatibility of construction needs
and cost-effective manufacturing sequences. JIT delivery for a steel contractor is ideally
sequenced in erection order. Cost-effective manufacturing for a (non-lean) steel fabricator would
be by member size. Thus, even when materials are delivered to the site in the erection order, they
are often produced and stored offsite in the manufacturer’s preferred fabrication sequence. For
this reason, one of the advantages of JIT, that of reducing buffers, is often not achieved in
construction. Buffers are simply moved upstream from the building site to the fabricator’s
storage area.
JIT
100%
JIT
100%
100%
100%
100%
100%
100%
80%
80%
60%
60%
40%
20%
0%
50%
40%
0%
0%
r
ne
s ig
De
li e
rs
Su
0%
bc
on
pp
r
c to
tr a
ac
n tr
Enterprise Level
Su
Co
Ow
ne
to r
r
20%
Project Level
Crew Level
JIT is a high-gain, high-risk strategy in construction. In general, the construction sequence is
variable; production is not steady state and is subject to substantial uncertainty. However,
contractors and subcontractors alike can produce substantial benefits by developing strategic
relationships with preferred suppliers. Owners that purchase long lead-time items must
coordinate with the contractor to appropriately schedule delivery of owner-furnished items.
7.1.6 Waste Elimination (Aspect 3: Production Scheduling)
100%
Subprinciple No. 4.8: Use Production Planning
and Detailed Crew Instructions, Predictable Task
Times. The heritage of construction is in guilds and craft
106
production. The craftsman controlled the means and methods of construction. Indeed, even
today, many workers are expected to arrive at the jobsite with their own tools of the trade.
Manufacturing has a different tradition. Tools and methods of production are provided by and
determined by the manufacturer. Accordingly, it is customary in manufacturing to employ
production engineers to help define and design production processes. Manufacturing engineers
determine sequence, materials, fixtures, jigs and tools for the work. They determine storage
location and processing times. In construction (with a few exceptions), all of the functions of the
production engineer are entrusted to the individual craftsperson or the first-line supervisor
(foreman). The disparity between the production engineering approach in manufacturing and the
lack of a production engineering tradition in construction can be explained, in part, by the highly
repetitive nature of most manufacturing tasks. Manufacturers can afford to spend effort on
optimizing the production system, knowing that they will reap benefits on every unit of
production. In construction, the means of production are often entrusted to the worker simply
because each production unit is somewhat unique (e.g., craftwork). However, craft workers are
not typically trained in the methods of production engineering. Often craft workers perform work
in the manner that they were first taught. There is not a practice of thinking about the most
efficient way to sequence the work, stage the materials or the myriad other details of a fully
formed production engineering approach.
Production Planning, Detailed Crew
Instructions
Production Planning, Detailed Crew
Instructions
100%
100%
100%
100%
Project Level
Crew Level
100%
100%
80%
80%
60%
40%
0%
0%
0%
40%
r
60%
20%
20%
De
s ig
ne
rs
pp
Su
ct
tr a
25%
0%
bc
on
li e
or
or
ct
ra
nt
Enterprise Level
Su
Co
O
wn
er
0%
Manufacturers can afford to spend a thousand dollars to save a dime on every unit produced.
Constructors do not have this luxury. However, given the cost of labor, and more specifically,
given the degree of waste prevalent in construction operations, contractors should do more to
focus on more effective production methods. This focus should not be to find faster ways to weld
or to erect steel. That is, the initial focus should not be on the value adding (VA) activities, but
rather on the non-value adding (NVA) activities. By planning worker sequences, material staging
and equipment allocation, production engineers can do much to reduce the 50 percent of the time
that is consumed by NVA activities. Contractors and subcontractors at every level of the
organization should start to move away from the craft approach to construction production toward
a more controlled and defined production attitude.
100%
Subprinciple No. 4.9: Implement Last Planner,
Reliable Production Scheduling, Short Interval
Schedules. Every lean contractor interviewed used some
method to organize, coordinate and plan the production aspects
of their work. Many contractors in this study used the last
planner system developed by the Lean Construction Institute.
107
Others started using the last planner system and then developed other systems that were more
suitable for their individual production systems. The use of a formalized production planning
system is a keystone of becoming a lean constructor. Production planning is not the same as
project planning. Project planning seeks to coordinate delivery of material, design and other
resources in accordance with a sequence of construction to support the required end date of the
project. Production planning is also not production engineering (refer to Subprinciple 4.8,
Subsection 7.1.6), which seeks to organize individual works tasks. Production planning is
systematizing the way in which various crews and subcontractors support the overall production.
To a large extent, production planning is obtaining commitments from individual crews and
subcontractors to perform a given work task by a specified time. These production commitments
are essential for the production planning of the downstream contractors. Part of the last planner
method is to track the proportion of the commitments that were kept by crews and subcontractors.
Metrics are used to measure the degree to which parties kept commitments, thereby allowing for
more reliable project schedules.
Last Planner/Reliable Scheduling etc.
100%
Last Planner/Reliable Scheduling etc.
100%
100%
100%
100%
Project Level
Crew Level
100%
80%
80%
50%
60%
40%
60%
25%
20%
40%
0%
r
De
s ig
ne
rs
pp
Su
tr a
25%
20%
0%
bc
on
li e
or
ct
ct
ra
nt
Enterprise Level
Su
Co
O
wn
er
or
0%
Production planning is just one more method used to gain control of the production process.
Production planning involves all of the contractors and subcontractors involved in the production
process. Designers and suppliers are involved in production planning to the extent to which
commitments for delivery of design or materials impede construction progress. Production
planning is primarily a field responsibility.
Subprinciple No. 4.10: Practice the Last Responsible Moment, Pull Scheduling. Pull scheduling is used
by manufacturers to help with production scheduling and to
reduce WIP. The notion of pull (as opposed to push) scheduling
is that a production item is pulled into the system only as it is
75%
needed. Specifically, demand by a downstream production task
indicates the need for production by an upstream task. Using
pull scheduling reduces WIP and increases throughput.
Conceptually, pull scheduling is very like “late start” scheduling in the Critical Path Method
(CPM). One lean contractor refers to construction pull scheduling as “scheduling at the last
responsible moment.” Since WIP is generated later in the construction process, the main benefit
of pull scheduling is a reduction in early cash requirements by the owner and contractors and less
site congestion. The main disadvantage is that pull scheduling uses project float. In the current
uncontrolled production environment, trading float for a reduction in WIP is a risky choice.
108
Last Responsible Moment/Pull Scheduling
Last Responsible Moment/Pull Scheduling
100%
100%
100%
100%
100%
Project Level
Crew Level
100%
100%
80%
80%
50%
60%
60%
40%
20%
40%
0%
0%
25%
r
ne
rs
Su
De
pp
s ig
li e
or
ct
tr a
0%
bc
Co
on
nt
O
ra
wn
ct
er
or
20%
Su
Enterprise Level
Pull scheduling is a field responsibility. Given the risky nature of a full pull schedule, the
concept must receive complete support from the executive level of the company.
Subprinciple No. 4.11: Use Small Batch Sizes,
Minimize WIP. Manufacturers use small batch sizes (or,
better yet, continuous flow manufacturing) to boost plant
throughput, reduce manufacturing cycle time and decrease WIP.
WIP reduction is a matter of considerable importance for the
manufacturer. Given the steady-state nature of manufacturing,
WIP creates a continuous inventory (partially completed goods)
75%
for the manufacturer that must be stored and financed until the
product is completed and sold. The nature of WIP is somewhat
different in construction. Most construction is accomplished using progress payments. From the
point of view of the typical contractor, WIP is actually production that can be “sold” at the end of
the period. Also, WIP might represent additional “factory space” for the contractor. For
example, for a high-rise building, each floor of the building frame that is completed represents
additional areas in which the contractors can work. However, from the point of view of the
owner, WIP is still inventory that will not produce revenue until it is put into service. The dual
nature of WIP in construction highlights another area of potential conflict and suboptimization in
construction.
Minimize WIP - Small Batch Size
100%
100%
75%
20%
40%
r
De
s ig
ne
rs
li e
pp
Su
0%
bc
on
Crew Level
25%
20%
Enterprise Level
Su
Co
nt
tr a
ra
ct
ct
or
or
0%
er
Project Level
60%
25%
40%
wn
100%
80%
60%
O
100%
100%
100%
75%
80%
Minimize WIP - Small Batch Size
109
Unlike most production decisions, WIP decisions directly affect cash flow and production
progress. Therefore, the owner of a lean jobsite must be involved with implementing WIP
reduction programs. This can be accomplished through changes to contract language and
strategy. Operationally, however, WIP reduction and use of small batch sizes are decisions
implemented by the field organizations.
Subprinciple No. 4.12: Use Decoupling Linkages,
Understand Buffer Size and Location. Buffers are
devices often used in construction to provide a cushion between
upstream crews and those downstream. In true lean production,
75%
buffers are discouraged because they increase WIP and cycle time.
Given the complexity and uncertainty of the construction production
process, limited use of buffers can help production scheduling on the project. For example, on a
high-rise building, a contractor may choose to provide for one empty floor between the
mechanical, electrical, and plumbing subcontractor and the following electrical subcontractor.
However, buffers as they are currently used in construction are a source of considerable waste.
Large material buffers on the construction site increase project time by requiring earlier design
and procurement actions to support early delivery of material. Buffers cause excess material
handling and increased carrying costs.
Decoupling Buffers, Buffer Size and Location
Decoupling Buffers, Buffer Size and Location
100%
100%
100%
Project Level
Crew Level
100%
100%
100%
80%
80%
60%
40%
25%
20%
60%
25%
40%
0%
0%
25%
r
s ig
ne
rs
De
Su
pp
li e
r
c to
tr a
bc
on
0%
Enterprise Level
Su
Co
nt
O
ra
wn
c to
r
er
20%
The use of buffers is an action taken in the field in coordination with production scheduling.
Buffer size can be reduced through appropriate cooperation with material suppliers (supply chain
management) and by appropriate release of design information.
7.1.7 Waste Elimination (Aspect 4: Product Optimization)
Subprinciple No. 4.13: Reduce the Parts Count, Use
Standardized Parts. Although lean design is specifically
excluded from this study, there are some obvious design actions that
will facilitate lean production. One is to use standard design details
and standard sized materials. At one case study site, a simple frame
distribution center, the steel design called for more than 40 different
sizes of bar joists. Each of the 40 shapes had to be designed, manufactured, shipped and
inventoried. If the design engineer had reduced the number of shapes to 20, considerable savings
would have accrued along the value stream. No doubt, the engineer was producing an
“optimized” design that reduced the weight of steel. However, from a production system view, a
100%
110
slight increase in material costs could easily be recovered by economies in procurement, material
handling and erection. At another site, long bar joists needed to be reinforced in the field by
welding bridging that ran between the joists at set intervals. The bridging was lifted to the level
of the joists and threaded through the web, positioned, measured and welded in place. This
activity consumed as much labor and equipment as did erecting the bar joist. Again, a design
solution that used a heavier joist that did not require bridging would have substantially saved
money in the field.
Standardized Parts
Standardized Parts
100%
100%
100%
100%
100%
100%
80%
80%
60%
40%
25%
60%
25%
20%
40%
0%
25%
25%
Su
r
De
s ig
ne
rs
pp
li e
or
tr a
0%
bc
Co
on
nt
O
ra
ct
ct
wn
or
er
20%
Su
Enterprise Level
Project Level
Crew Level
Using standardized parts and reduced parts count is a cooperative activity between the designer
and contractor or subcontractor. The owner can influence the use of this principle by the choice
of a project delivery system. Design-build projects have a better chance of optimizing design to
allow lean construction.
Subprinciple No. 4.14: Use Pre-Assembly and Prefabrication. Pre-assembly
and prefabrication are not new concepts for construction. However,
any action that removes labor from the relatively uncontrolled field
environment to the more controlled shop environment promises to
100%
improve quality and reduce labor costs. Manufacturers have
increasingly used more pre-assembly from their vendors. For all of
their apparent benefits, pre-assembly and prefabrication are rarely
used in construction. For example, at two of the process piping jobsites that were visited, large
bore process piping was field fabricated onsite rather than using a fabrication plant.
Pre-assembly and Prefabrication
Pre-assembly and Prefabrication
100%
100%
100%
100%
100%
100%
100%
80%
80%
60%
40%
60%
25%
20%
40%
r
De
s ig
ne
rs
pp
Su
tr a
25%
20%
0%
Enterprise Level
Su
bc
on
li e
or
ct
ct
ra
nt
Co
O
wn
er
or
0%
50%
111
Project Level
Crew Level
Adopting more pre-assembly and prefabrication is a choice that must involve the owner.
Generally, prefabrication will require a higher early case flow. Pre-assembly and prefabrication
decisions require close cooperation between designer, supplier and construction.
Subprinciple No. 4.15: Use Preproduction Engineering and Constructability Analysis. Constructability
analysis or preproduction engineering is not a new idea in
construction. The ability to use constructability analysis is limited
by the project delivery system chosen for the job. The value
generation process used in construction often encourages
suboptimization by the various players in the process. Cooperative
project delivery arrangements allow for more effective use of
100%
constructability methods.
Preproduction Engineering/Constructibility
Preproduction Engineering/Constructibility
100%
100%
100%
100%
100%
100%
100%
80%
80%
50%
60%
60%
40%
20%
50%
40%
r
ne
rs
s ig
0%
De
pp
Su
tr a
20%
0%
Enterprise Level
Su
bc
on
li e
or
ct
ct
ra
nt
Co
O
wn
er
or
0%
Project Level
Crew Level
As with prefabrication, effective constructability processes require close cooperation between
designer, supplier and construction. Often the crew is one of the best sources for good
constructability ideas.
7.1.8 Continuous Improvement and Built-In Quality
Subprinciple No. 5.1: Prepare for Organizational
Learning and Root Cause Analysis.
Stability in
manufacturing is a tremendous advantage to a company that is
attempting organizational learning. Manufacturers will devote
substantial time toward understanding why a defect occurred or why
a process failed. They do so against the backdrop of a steady-state
manufacturing setting in which suppliers, machinery and personnel change more slowly than in
the construction domain. In contrast to manufacturing, construction organizations are (by nature)
temporary project organizations. Not only do personnel change from project to project but the
companies (subcontractor, suppliers) that make up the projects change. The dynamic nature of
the construction organization makes it more difficult, and all the more important, to create a
learning organization. Also, construction operations can be dispersed across regions, the country,
or even the world, making it difficult to sustain a corporate culture of improvement. Yet,
continuous improvement and the relentless elimination of waste are linchpins of the lean process.
100%
112
Organizational Learning
100%
100%
100%
100%
100%
75%
80%
75%
75%
80%
60%
60%
40%
20%
50%
40%
0%
0%
r
s ig
De
pp
Su
bc
on
0%
Enterprise Level
Su
Co
ne
rs
li e
or
ct
tr a
ra
nt
O
wn
ct
er
or
20%
Project Level
Crew Level
The impetus for creating a learning organization must originate at the highest levels of the
contractor organization. It is the responsibility of the field office to execute organizational
practices. To the extent possible, subcontractor, designer and supplier strategic partners should
be included in learning and root cause analysis.
Subprinciple No. 5.2: Develop and Use Metrics to
Measure Performance, Use Stretch Targets. It has been
said, “If you are not measuring your results, you are just practicing.”
Lean manufacturers develop and use a wide array of metrics to
measure performance. Quality, cost, financial and other aspects of
company performance are represented by metrics. Those metrics are
then used to establish goals (stretch targets) for process improvement. Manufacturers use
sophisticated quality performance and quality metrics that are made possible by the stable
manufacturing domain. Manufacturers also use many metrics that are unusual in construction.
Manufacturers use measures of throughput, cycle time and Takt time to examine the state of the
manufacturing system. It was Einstein who said, “Not every thing that counts is countable, not
everything that is counted counts.” Yet, if an organization understands the purpose, even an
imperfect metric will be useful. The metric that was called VA work in the value stream studies
is subject to criticism because it narrowly defines the nature of work included in the definition.
Yet, if it is understood that the purpose of the metric is to highlight the number of tasks that fall
outside of this definition, its rigorous nature is more defendable.
100%
Initially, as construction goes lean, some of the standard “lean metrics” used in manufacturing
may not be significant metrics for construction. As the value stream analysis showed, the amount
of waste (NVA) activities that exists in the typical construction process should encourage
development of metrics to help identify and eliminate waste. After production operations become
more efficient, the industry can start to focus on more traditional metrics that measure the
effectiveness of the VA processes.
Metrics
Metrics
100%
100%
100%
100%
100%
80%
80%
100%
60%
60%
40%
25%
25%
25%
20%
40%
0%
25%
r
s ig
ne
rs
De
pp
Su
tr a
0%
Enterprise Level
Su
bc
on
li e
or
ct
ct
ra
nt
Co
O
wn
er
or
20%
113
Project Level
Crew Level
Since metrics are cross-company measures, the leadership for their institution must come from
the enterprise level. The owner also has a role to play by allowing project performance to be
measured by nonstandard means. It is a “leap of faith” to establish a new performance
measurement standard and the owner’s support in these endeavors is crucial. Field management’s
role is to implement the metrics and field crews must be trained in their importance.
Subprinciple No. 5.3: Create a Standard Response to
Defects. A standard response to a defect is almost a subset of
creating an environment for organizational learning. A standard
procedure allows quick response and systematic understanding of the
cause of the defect. In the value stream studies, multiple instances of
rework were observed. In each instance, the goal was to rectify the
fault quickly and efficiently. However, in only one instance was a process seen that tried to
understand the cause of the fault and ensure that it would not occur on future jobs.
100%
Defect Response Plan
Defect Response Plan
100%
100%
100%
100%
100%
75%
80%
80%
60%
40%
25%
20%
60%
25%
50%
40%
0%
r
De
s ig
ne
er
s
Su
p
tr a
20%
0%
Enterprise Level
Su
bc
on
pli
or
ct
ct
ra
nt
Co
O
wn
er
or
0%
Project Level
Crew Level
A standard response plan is created by corporate management to reduce future defects by alerting
other projects to the nature of the problem and its causes. A standard response plan should
provide field management with a reliable way of correcting the defect. Defects in subcontractor’s
work must be managed in the same careful manner as those in prime contractor work. Feedback
to designers and suppliers is a key ingredient of a standard response plan.
Encourage Employees to
Develop a Sense of Responsibility for Quality. “Stop
the line,” a maxim that originated with the Toyota Production
System, relates to the practice that allows all assembly workers to
stop the entire production line if they observe a defective product at
their work stations. This maxim implies that is unacceptable to send
defective work to the next work station. It is every worker’s responsibility to proactively manage
quality. The lean ideal is to build quality in, not to inspect quality in. For the most part, the
construction industry continues to inspect quality in. Rework and punchlist items continue to
consume a large fraction of labor costs. The nature of the industry, including the prevalence of
temporary workers, union hiring rules and the interdependency of work tasks, makes it difficult to
establish this philosophy in the construction production environment.
100%
114
Employee Responsibility for Correcting Defects
Employee Responsibility for Correcting Defects
100%
100%
100%
100%
Project Level
Crew Level
100%
100%
80%
80%
60%
60%
20%
0%
0%
0%
40%
r
40%
20%
De
s ig
ne
rs
pp
Su
tr a
25%
0%
Enterprise Level
Su
bc
on
li e
or
ct
ct
ra
nt
Co
O
wn
er
or
0%
Developing the concept of personal responsibility for quality is the province of field management.
Some lean contractors maintain a cadre of key field people to act as guides and mentors for craft
workers who are hired temporarily for a project.
7.2 An Information-Based Perspective on Lean Principles
The preceding analysis of the lean principles that apply to construction is based on the experience
of the research team and the early adopters who participated in the study. Chapter 3.0 catalogued
some of the fundamental differences between manufacturing and construction. This section
reexamines these differences to validate the analysis of which lean principles best apply to
construction.
Some of the differences between manufacturing production and construction production (e.g., the
role of the owner in design of the product) arise from the dissimilar nature of the respective
businesses. However, a review of Chapter 3.0 suggests that the majority of the differences
between manufacturing and construction resolve themselves into one factor: the stability of the
manufacturing environment compared to the construction production environment. Application
of lean principles to construction must account for the inescapable fact that manufacturing takes
place in a steady-state environment (established design, stable machinery and plant, long-term
supplier relationships, long-standing employees, etc.), and construction production is the
converse. The absence of steady-state operating conditions introduces variability and uncertainty
into the production process. Therefore, one way to identify which principles are appropriate for
construction is to evaluate whether the principle serves to make the production system more
stable or, alternatively, whether the principle serves to reduce the negative impacts of
nonreducible uncertainty.
Because of the repetition and certainty in the manufacturing environment, manufacturers can use
assembly lines and production systems to guide products with high efficiency through the
production cycle. Construction processes are repetitive only at the task level, and the production
facilities are rarely static. Instead of using assembly lines and other production systems to govern
production flow, sequence and throughput, construction often uses an increased level of planning.
As a consequence, lean construction production involves handling an increased amount of
information. Construction production is already dependent on up-to-date project information.
Information that describes progress by upstream contractors, changes to design and status of
material deliveries is central to the effective operation of construction production systems.
Construction managers already use face-to-face meetings, emails, memos and telephone
conversations to gather and disseminate such information. From the perspective of construction
115
managers, the desirability of applying any given lean principle is partially contingent on whether
the principle increases the current information handling requirements of the construction team.
Those principles that create conditions that are closer to manufacturing (i.e., more stability) will
ultimately reduce information processing demands and will be attractive principles to apply.
Those principles that increase the information processing demands without a concomitant
increase in system stability will be attractive only to the extent that the increased information
workload improves quality, reduces costs or increases the reliability of the schedule.
A perspective on how organizations react to increased information processing needs is suggested
by the work of Galbraith (1974). Galbraith’s work starts from the proposition that greater task
uncertainty requires an organization to process more information because it is difficult to plan and
schedule the execution of uncertain tasks. Therefore, during actual execution of the task, the need
for more knowledge and information processing leads to changes in schedules and resource
assignments. Since organizations are limited in their ability to process information, they institute
strategies for dealing with this limited ability. Generally, organizations deal with the increased
information processing demands by using the following strategies:
•
Increasing coordination through rules and procedures.
•
Creating strong hierarchies to deal with the exceptions that uncertainty creates.
•
Establishing clear targets and goals that allow lower organizational levels
increased discretion and responsibility.
If these organizational strategies are inadequate to deal with the uncertainty, organizations may
react in one of the following ways:
•
Decreasing the informational processing needs by creating “slack resources,”
e.g., contingency funds, contingency time or capacity and material buffers.
•
Increasing the organization’s ability to deal with information through the creation
of information processing systems (meetings, reports, computer systems) or by
creation of “lateral” relationships (coordinators, teams, task forces) that cut
across hierarchies.
To help confirm the experientially based conclusions about which principles are applicable to
construction, each principle was reevaluated using the following three conditions:
1.
The principle, without the need for increased planning or information handling,
reduces the uncertainty in the production environment.
2.
The principle requires increased planning and information handling that will lead
to a more stable production environment and reduce the negative effects of the
instability.
3.
The principle requires increased planning and information handling that will
reduce the negative effects of the uncertain production environment, e.g., high
costs, poor quality, unreliable execution.
116
Tables 7.1 through 7.3 group the subprinciples into one of these three categories and describe the
information handling mechanism used to apply the principle.
7.3 Applying Lean Principles to Construction
An appropriate, practical set of lean principles for the construction industry would be invaluable
for companies searching for ways to improve productivity and quality and reduce costs. The
principles established in this chapter can be used as a guide toward creating a construction
organization that moves closer to the ideal of lean production. This process must involve the
entire organization and address all aspects of lean production: customer focus, culture and
people, workplace organization, waste elimination and continuous improvement. Chapter 8.0
discusses the application of lean principles in construction organizations.
117
Table 7.1: Principles that Reduce Uncertainty in the Production Environment
without Increased Planning or Information Handling
Principle
Subprinciple
Mechanism
Customer Focus
Cross Train Crew Members
Create Slack Resources
Use Flexible Resources
Ensure Management
Commitment
Establish Clear Target and Goals
that Allow Increased Employee
Discretion
Encourage Employee
Empowerment
Discretion
Use 5S’s
Discretion
Provide Visual Management
Discretion
Develop and Use Metrics
Discretion
Create Standard Response to
Defects
Discretion
Encourage Employees to
Develop Responsibility for
Quality
Discretion
Culture and People
Workplace
Organization and
Standardization
Continuous
Improvement and
Built-In Quality
118
Table 7.2: Principles that Require Added Planning or Information Handling
but Reduce Uncertainty in the Production Environment
Principle
Subprinciple
Mechanism
Customer Focus
Meet Customer Requirements
Establish Lateral Relationships
Culture and People
Define Value from Viewpoint
of Customer
Provide Training
Workplace
Organization and
Standardization
Work with Suppliers and
Subcontractors
Implement Error-Proofing
Devices
Create Defined Work Processes
Waste Elimination
Create Logistic Material
Movement and Storage Plans
Minimize Double Handling and
Worker and Equipment
Movement
Remove Material Constraints
Understand Buffer Size and
Location
Reduce Difficult
Setup/Changeover
Use Total Productive
Maintenance
Use Production Planning and
Detailed Crew Instructions
Implement Last Planner,
Reliable Production Scheduling
Use Standard Parts
Continuous
Improvement and
Built-In Quality
Use Pre-assembly and
Prefabrication
Use Preproduction Engineering
and Constructability Analysis
Prepare for Organizational
Learning
119
Increase Coordination Using
Rules and Procedures
Create Strong Hierarchies
Increase Coordination with Rules
and Procedures
and Procedures
and Procedures
and Procedures
and Procedures
and Procedures
and Procedures
and Clear Target and Goals that
Allow Increased Employee
Discretion
and Procedures
and Procedures
and Procedures
Increase Information Processing
Ability Using Information
Systems
Table 7.3: Principles that Require Added Planning or Information Handling but
Reduce the Negative Effects of Instability in Production
Principle
Subprinciple
Mechanism
Customer Focus
Use Target Costs and Value
Engineering
Increase Information Processing
Ability Using Information
Systems
Waste Elimination
Balance Crews and
Synchronize Flows
(Opposite of Creating Slack
Resources)
Reduce Scrap
Resources)
Use JIT Scheduling
Resources)
Practice Pull Scheduling
Resources)
Use Small Batch Sizes and
Minimize WIP
Resources)
120
8.0 Conclusions and Recommendations
8.1 Reasons to Apply Lean Principles to Construction
The project team reviewed the combined findings of research into lean construction and
determined that there is an extraordinary opportunity for individual companies to develop worldclass production systems by carefully applying lean principles to the construction process.
Although the project delivery process was not studied in detail, there is clearly a coupled
opportunity to apply lean thinking to the supply chain and design and contracting processes to
create what the Lean Construction Institute calls a Lean Project Delivery Process.
Investigations of the construction production process indicated that construction activities are
typically only 10 percent value adding (VA). If a contractor could improve the VA portion to just
15 or 20 percent, the lean contractor would have a significant competitive advantage. However,
when one looks at construction operations with “lean eyes,” little standardization or preplanning
is evident. In fact, the construction process includes little that manufacturing engineers would
recognize as production planning or production engineering. Often, the design of construction
operations is consigned to the individual crews. While the crew members often have the skill and
experience to design specific construction operations, typically they do not have the training or
the mind-set that will lead to a lean operation.
Some will contend that construction is too different from manufacturing to expect
“manufacturing-like” lean results. While acknowledging that manufacturing and construction
operate in different environments and that lean in construction will be more difficult than lean in
manufacturing, interviews with early adopters of lean construction principles cited increased
quality, increased safety, better schedule performance and decreased costs as some of the benefits
of starting the lean journey.
8.2 Path Forward to Becoming Lean
Observations of early adopters of lean principles suggest that there is no one prescribed way to
become lean. Each early adopter in this study used a different starting point, and each progressed
along the path at a different rate. However, based on the totality of the research, the evidence
suggests that an engineering, procurement and construction (EPC) company that wants to start a
lean process should start with its field operations.
8.2.1 Identify Waste in Field Operations
There is historical precedent for starting with production activities; Toyota started its lean work
by concentrating on its shop floor. Starting lean activities with field operations also has a good
rational basis because value is added (from the customer’s viewpoint) during the construction
process. Finally, the strict value definition that was used for the field studies1 provides a lens
through which one can start to identify waste in the field processes.
1
“…any activity that changes the shape, form, or function of materials or information to meet
customer’s needs” (Walbridge-Aldinger 2000).
121
8.2.2 Drive Out the Waste
After a type of waste has been identified, the next step is to drive it out. A given type of waste
(e.g., rework) might have one or several different causes. To drive out the waste, the root cause
must be understood. If the root cause is worker training, design errors or tolerance errors from an
upstream crew, appropriate steps should be taken to eliminate or reduce the waste on future work.
The process of driving out waste leads naturally to many of the other lean principles such as
constructability reviews and Just-In-Time (JIT) scheduling. The EPC contractor should start by
concentrating on the non-value adding (NVA) (i.e., pure waste) activities. With construction
averaging 50 percent NVA activities, there are ample opportunities to reduce these wastes before
turning to the non-value adding but required (NVAR) or VA activities.
8.2.3 Standardize the Workplace
After lean practices have been identified, they should be formalized as company standards.
Developing standard practices for construction processes reduces the information burden on the
crew members. One early adopter contractor that was studied created identical gang boxes so that
the crews knew what tools were commonly available and where to find them.
8.2.4 Develop a Lean Culture
Depending upon how much of the value stream a company controls (i.e., construction only or
EPC), the processes should be formalized within the organization and with strategic partners,
subcontractors and suppliers. One early contractor spent considerable effort training its entire
staff and most of its supplier and subcontractor staffs. Other lean early adopters trained key
partners on a project-by-project basis. A key difference between manufacturing and construction
is the rapidity with which construction partnerships and alliances change with time and location.
8.2.5 Get the Client Involved with the Lean Transformation
After a company has experience with lean principles, its clients should be educated about the
benefits, costs and risks of going lean. The company should start defining value from the
customer’s viewpoint. In some cases, the impetus for going lean has actually originated with a
client organization that had experience with the successes of lean manufacturing.
8.2.6 Continuously Improve
With all of the above steps under way, a company can start to improve on improvements.
Everyone involved with the project should begin to understand their responsibility for reducing
waste and improving quality. Continuous improvement requires that lean practices and lean
culture be the common basis for doing business.
8.3 Barriers to Developing a Lean Company
There are several barriers to “going lean” in construction that are not found in a manufacturing
environment. The following subsections review the most significant barriers to lean construction.
122
8.3.1 Little General Understanding of Lean
Unlike manufacturing, there is little understanding of lean practices or potential among
construction personnel. Lean has made significant inroads into construction in those
environments where lean practices are commonplace in other aspect of the business environment;
e.g., automotive, pharmaceuticals. Due to the innate differences between manufacturing and
construction, there is significant skepticism concerning the applicability of lean principles to
construction.
8.3.2 Unique Projects and Unique Design
Manufacturers develop their lean practices and systems over long production runs. Manufacturers may produce a million or more units before there is a significant change to a product
line. Long stable production runs allow manufacturers to fine-tune processes and relationships to
a degree that is not feasible in construction. This lack of long-term, repetitive projects limit the
degree to which lean can be fully implemented. On the other hand, many EPC projects have
multi-year construction schedules that will allow ample time to develop lean practices.
8.3.3 Lack of Steady-State Conditions
Again as contrasted to manufacturing, construction suffers from lack of steady-state conditions.
Most contractors perform several different types of work, in different locales, with different
clients. It is difficult to reposition lean practices from one job or location to another. Often it is
not feasible to maintain a relationship with a key supplier for projects that are located across the
country or around the world.
8.3.4 No Control of the Entire Value Stream
Manufacturers control their value stream. They control design details, materials and the
production environment. Construction companies rarely pick the site, often do not control the
design and are frequently constrained to develop strategic relationships based on a low-bid model.
The lack of control of the entire value stream makes a case for stronger owner involvement in the
lean process. An owner that fully understands the importance of lean as a “system of interacting
behaviors” will be more amenable to changes in project design and project delivery so that the
full potential of the lean concept may be realized.
8.4 Future Research
The research team was charged with investigating lean principles to determine whether lean
practice holds potential for improving construction. The conclusion is an unequivocal YES!
However, the sheer scope of other potential lean applications is daunting. The following
subsections propose areas where follow-up work will enhance understanding of the significance
of lean principles in construction.
8.4.1 Lean Coordination
For this study, the value stream analyses were conducted at the worksite. There is an entire set of
analyses that should be conducted at the level of interacting crews/subcontractors. It is at this
interface where the true value of buffers and pull scheduling may be most apparent. This topic
can be broadened to include the entire supply chain.
123
8.4.2 Economics of Lean
The economics of manufacturing and construction are different. Minimizing inventory and WIP
is important for a manufacturer because inventory is essentially steady-state; i.e., it is always
there. Construction production experiences fluctuating levels of inventory that are less noticeable
from day to day. Also, manufacturers own their inventory and WIP until they are converted into
sales. In contrast, a contractor’s inventory and WIP are often converted to revenue by the
progress payment process. Finally, from the owner’s viewpoint, the cost of a facility (chip
fabrication, pharmaceutical plant) is often a very small portion of the project’s life-cycle cost.
The owner is often more focused on maintaining schedule than on controlling costs.
8.4.3 Importance of Repetition
Manufacturers develop lean principles to a much higher degree than do EPC companies because
of the high degree of repetition in manufacturing. Some types of construction (high-rise
buildings, single-family home developments) have a higher amount of inherent repetition than do
other types of construction. What is the importance of repetition as regards implementing lean
principles in construction? What is the importance of “granularity” of the repetition? For
example, if the work of only one crew is repetitive (e.g., a repetitive foundation), how does that
compare to an entire project (e.g., a single-family house) that is repetitive?
8.4.4 Reliability in Construction
Ensuring reliable construction schedules is fundamental to attaining efficient production systems
and interfaces. Reliable construction schedules are required to schedule deliveries and to make
subcontract time commitments. One can achieve reliability either by trying to synchronize
production systems (additional planning) or by building time buffers (in the form of WIP and
inventory buffers) between trades.
8.4.5 Metrics for Lean Construction
It has been said that if you are not measuring, you are only practicing. Continuous improvement
suggests that the results obtained from applying lean principles need to be measured and benchmarked. Lean manufacturers use many metrics to measure lean performance (e.g., inventory
turns, throughput, cycle time). The appropriate metrics for measuring lean construction performance need to be determined, which is beyond the scope of this report.
124
Appendix A
Case Study No.1 - Structural Steel
1.0 Overview
1.1 Project Goal
The purpose of this case study was to collect data to develop a value stream map for the
construction process. Observation was limited to structural steel erection. Field data gathered on
two separate value streams included the following: the actual flow of the steel from the time it
arrived on the jobsite until it was erected into final position, and the flow of worker activities
performed to erect the steel.
Data collection was accomplished in two consecutive days. Data observations were recorded on
prepared data sheets. The steel erection crew consisted of the following six workers: four
laborers, a forklift operator and a crane operator. Each of the crew members was individually
monitored by one member of the data collection team. Each observer was equipped with a
stopwatch and a clipboard with the data sheets. Two digital video cameras were positioned to
view the activity area at views intersecting at 90 degrees. The videotapes were taken to provide a
means for a more detailed analysis of the activities.
Data was recorded as the activities occurred. An entry was made on the data sheet each time a
new task was started. For example, an entry might indicate that a worker was rigging a bar joist
for the crane. The next entry might indicate that the worker was waiting until the crane had
lowered its hook so the worker could attach the rigging to the hook. The elapsed time for each
task was recorded as well as the observer’s judgment regarding whether the task was value
adding (VA), non-value adding (NVA) or non-value adding but required (NVAR).
1.3 Project Description
The project was a 200,000 square foot warehouse. The warehouse was 660 feet long and 300 feet
wide. The entire area was divided into 55 bays, each measuring 60 feet by 60 feet. The team
observed the erection activities associated with four bays. The subset of the observed operations
formed part of the overall sequence of steel erection. The steel erection activities were preceded
by the foundation work, which was succeeded by the installation of steel bridging between joists,
final aligning, and bolting of the structure. The steel erection activities were partially constrained
by the fact that foundations along one column line were not yet installed. The team observed
little impact on the efficiency of the steel erection activities caused by the constraint. However,
late installation of these foundations will cause unnecessary equipment moves and other
inefficiencies after this observation period.
2.0 Steel Erection Process
Steel erection consists of the following three distinct cycles: column, girder and bar joist erection.
The pictures on the following page illustrate the erection cycle. The process starts with a column
erection along a bay section. Generally, the crane can reach three columns without moving; each
125
Step 1: Column Erection
Step 2: Support Bar Joist
Step 3: Next Column Erected
Step 4: Support Bar Joist Erected Along
with Girder
Step 5: Final Column Erected
Step 6: Final Girder Erected
Step 7: Interior Bar Joist Installed
126
column is pre-positioned at the time of shakeout, with its baseplate oriented toward the
appropriate foundations and anchor bolts. Next, girders are placed between columns. Finally, bar
joists are erected. Typically, two bar joists are erected between each bay along the column line to
provide stability while the remainder of the bay is erected. Once all the columns, girders and
stabilizing bar joist are erected along a column line, the interleaving bar joists are installed in a
highly repetitive process.
For this case study, the configuration of the building frame necessitated that the steel erection
crew perform three separate tasks. The sequence of tasks required movement from location to
location, and each task also required a different mix of equipment and workers. Therefore, in
contrast to a highly repetitive manufacturing sequence, it was very difficult to design an erection
sequence that had the correct number of workers or equipment for each of the three separate
tasks. The contractor for this case study chose to size the crew and equipment mix to be most
efficient at the bar joist erection stage.
The following materials were installed during the observation period:
•
Two columns.
•
Two girders.
•
27 bar joists.
Likewise, the following equipment and crew structures were observed:
•
One forklift.
•
Three sky lifts (Genie lifts).
•
One boom crane.
•
One boom crane operator.
•
Four to five personnel in the steel erection crew.
The following section analyzes each worker’s contributions to each cycle. Tables and figures
were developed for each worker and task. The tables and figures describe the time spent on VA,
NVA and NVAR actions within each cycle.
2.1 Observation of Steel Erection Process
In the following subsections, each worker is referred to by the position that he or she occupied
during the bar joist cycles. These references are used for all other cycles to maintain consistency
throughout the analysis. (Refer to the end of this case study to review the data sheets.)
2.1.1 Column Erection Cycle
The column erection cycle consisted of the following tasks: preparing the column base, rigging
the column for the crane to lift, guiding the column into place, bolting the column to the
foundation and unhooking the rigging from the column. Figure A.1 shows the major tasks
127
required to complete the steel erection. The shaded areas are used to visually indicate that some
tasks took longer to complete than others, and that those tasks could occur simultaneously with
other tasks. The shaded regions are not intended to show actual task durations (e.g., two hours to
rig the steel member for the crane).
Column Erection
1
2
3
4
5
6
Task Order (process flow is shown, NOT TIME)
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Prepping Column Base
Rigging Column for Crane
Column Lifted into Place
Column Base Bolted Down
Rigging Unhooked from Crane
Plumbing Columns
Note: This schedule is based on a five day workweek; weekends are excluded.
Typically after girders are in
position between columns.
Figure A.1: Critical Path Method (CPM) Schedule for a Column Erection Cycle
Only two members of the crew, the forklift operator and the left connector, were involved with
this activity. The two other crew members were not needed for this task and, therefore, all of
their time was classified as NVA.
The forklift operator was responsible for bracing the columns with the forklift, while the
alignment and bolting of the column to the baseplate occurred on the ground. Table A.1 and
Figure A.2 show the VA, NVA and NVAR values for the forklift operator. During the column
cycles, the forklift operator spent most of his time performing NVAR actions. The only VA
actions for the forklift operator occurred while bolting the column to the baseplate.
Table A.1: Column Data for the Forklift Operator
VA
% of Total Time
0:02:33
6.83%
0:02:33
6.83%
0:05:05
0:06:09
13.62%
16.48%
0:11:14
30.10%
0:02:36
0:01:28
0:19:28
6.97%
3.93%
52.17%
NVAR Total
0:23:32
63.06%
Grand Total
0:37:19
100.00%
Value Adding
VA Total
NVA
Waiting
Motion
NVA Total
NVAR
Mat. Pos.
In-Process-Ins.
T.W.S.A.
128
Forklift Operator - Column Cycle
VA
7%
NVA
Waiting
14%
NVAR
TWSA
52%
NVA Motion
16%
NVAR Material
Positioning
7%
NVAR In-Process
Inspections
4%
Figure A.2: Column Data for the Forklift Operator
The left connector was responsible for aligning the column and bolting the column to the
baseplate. Table A.2 and Figure A.3 show the VA, NVA and NVAR values for the left
connector. The majority of the left connector’s time was NVA and was spent waiting and/or
moving machinery (sky lift). The left connector was only involved in bolting one of the columns.
Table A.2 and Figure A.3 show that 13 percent of the time was spent on bolting, while 87 percent
of the time was spent on wasted actions.
Table A.2: Column Data for the Left Connector
VA
Value Adding
% of Total Time
0:02:00
13.42%
0:02:00
13.42%
0:05:59
0:06:55
40.16%
46.42%
NVA Total
0:12:54
86.58%
Grand Total
0:14:54
100.00%
VA Total
NVA
Waiting
Motion
129
Left Connector - Column Cycle
VA
13%
NVA Motion
47%
NVA Waiting
40%
Figure A.3: Column Data for the Left Connector
The right connector and X-bracing connector had limited involvement with the column cycles.
Table A.3/Figure A.4 and Table A.4/Figure A.5 show the VA, NVA and NVAR values for each
crew member.
Table A.3: Column Data for the Right Connector
NVA
% of Total Time
0:06:00
0:02:00
53.02%
17.67%
0:08:00
70.69%
0:03:19
29.31%
NVAR Total
0:03:19
29.31%
Grand Total
0:11:19
100.00%
Waiting
Motion
NVA Total
NVAR
Mat. Pos.
130
Right Connector - Column Cycle
NVAR Material Positioning
29%
NVA Waiting
53%
NVA Motion
18%
Figure A.4: Column Data for the Right Connector
Table A.4: Column Data for the X-Bracing Connector
NVA
% of Total Time
0:10:30
0:05:30
65.63%
34.38%
NVA Total
0:16:00
100.00%
Grand Total
0:16:00
100.00%
Waiting
Motion
X-Bracing Connector - Column Cycle
NVA Motion
34%
NVA Waiting
66%
Figure A.5: Column Data for the X-Bracing Connector
131
2.1.2 Girder Erection Cycle
The girder erection process detailed on Figure A.6 included the following subtasks: rigging the
girder, guiding the girder into hands of crew members stationed at the top end of the columns,
adjusting/hammering the girder to fit into slots, bolting the girder into place and unhooking the
crane rigging from the girder.
Girder Erection
1
2
3
4 5
6
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Two Columns Erected
Rigging Girder for Crane
Girder Erected into Place
Aligning Girder
Bolting Girder into Place
Unhooking Rigging from Crane
Plumbing Structure
Occurs simultaneously with
column plumbing
Figure A.6: CPM Schedule for Girder Erection
Data for the four remaining crew members is presented below.*
The forklift operator focused on setting up the rigging for the crane and guiding the girder into
the hands of the crew members above. Table A.5 and Figure A.7 show the VA, NVA and NVAR
summary values for the forklift operator. During the girder cycle, the forklift operator spent most
of the time waiting (approximately 66 percent). None of the forklift operator’s actions were VA.
The only NVAR actions of the forklift operator were rigging the girder and guiding it while it
was being lifted by the crane.
Table A.5: Girder Data for the Forklift Operator
Activity C lassification
NV A
W aste C lassification
W aitin g
T ran spo rt
M otion
NV A T otal
T otal T im e at Activity
% of T otal T im e
0:15:50
0:00:40
0:02:37
65.61%
2.76%
10.84%
0:19:07
79.21%
NV AR
M at. P o s.
0:01:33
6.42%
T .W .S.A.
0:03:28
14.36%
NV AR T otal
0:05:01
20.79%
G rand T otal
0:24:08
100.00%
*Four members of the five-man crew were observed during the girder erection cycle. The fifth observer
was unable to record data during this period.
132
Forklift Operator - Girder Cycle
NVAR TWSA
14%
6%
NVA Motion
11%
NVA Waiting
66%
NVA Transport
3%
Figure A.7: Girder Data for the Forklift Operator
The left connector performed the following actions: maneuvered the girder to fit into the sleeve
connection point on the column, made final adjustments and bolted the girder into place.
Table A.6 and Figure A.8 show the VA, NVA and NVAR times for the left connector.
Table A.6: Girder Data for the Left Connector
VA
Value Adding
VA Total
% of Total Time
0:06:00
15.50%
0:06:00
15.50%
0:04:30
0:17:00
11.63%
43.93%
NVA
Waiting
Extra Proc.
Motion
NVA Total
0:00:55
2.37%
0:22:25
57.92%
NVAR
0:10:17
26.57%
NVAR Total
Mat. Pos.
0:10:17
26.57%
Grand Total
0:38:42
100.00%
133
Left Connector - Girder Cycle
VA
16%
27%
NVA Waiting
12%
NVA Motion
2%
NVA Extra Processing
43%
Figure A.8: Girder Data for the Left Connector
The right connector accomplished the following: maneuvered the girder to fit into the sleeve
connection point on the column, made final adjustments and bolted the girder into place.
Table A.7 and Figure A.9 show the VA, NVA and NVAR data for the right connector. The left
and right connectors’ responsibilities were the same for the girder cycle; these included operating
the sky lift, aligning and positioning the girders and bolting each member into its final place.
During the girder cycle, both connectors spent the majority of their time aligning and fitting the
girder into place. During one of the girder cycles, approximately 24 minutes of hammering and
adjustments were needed to fit the girder in place. The remaining time was spent bolting the
girder and waiting on other team members.
Table A.7: Girder Data for the Right Connector
VA
Value Adding
% of Total Time
0:04:50
15.50%
0:04:50
15.50%
0:07:30
0:18:51
24.05%
60.45%
NVA Total
0:26:21
84.50%
Grand Total
0:31:11
100.00%
VA Total
NVA
Waiting
Extra Proc.
134
Right Connector - Girder Cycle
VA
15%
NVA Waiting
24%
NVA Extra
Processing
61%
Figure A.9: Girder Data for the Right Connector
Finally, the x-bracing connector was responsible for releasing the crane rigging from the girder
after the member was in place and secured between the two columns. Table A.8 and Figure A.10
show the VA, NVA and NVAR data for the x-bracing connector.
Table A.8: Girder Data for the X-Bracing Connector
NVA
% of Total Time
0:31:45
0:00:15
86.99%
0.68%
0:32:00
87.67%
0:04:30
12.33%
NVAR Total
0:04:30
12.33%
Grand Total
0:36:30
100.00%
Waiting
Motion
NVA Total
NVAR
T.W.S.A.
135
X-Bracing Connector - Girder Cycle
NVAR TWSA
12%
NVA Motion
1%
NVA Waiting
87%
Figure A.10: Girder Data for the X-Bracing Connector
The majority of the x-bracing connector’s time was NVA. Table A.8 shows that more than one
half hour was spent on waiting. The x-bracing connector’s only physical involvement with the
girder cycle was the release of the crane rigging after the left and right connectors secured the
girder.
2.1.3 Bar Joist Cycle
The bar joist cycle detailed on Figure A.11 included the following subtasks: bolting the x-bracing
to the bar joists while it was on the ground, attaching the rigging, maneuvering the bar joist into
the hands of the connectors, aligning and positioning the bar joist into its final position on the
structure, bolting the bar joist, attaching the x-bracing to the adjacent bar joist already in place on
the structure and releasing the crane rigging from the bar joist.
Bar Joist Erection
1 2 3 4 5
6
Task Order (process flow is shown, NOT TIE)
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Columns and Girders Erected
X-Bracing Attached on Ground
Rigging Bar Joist for Crane
Bar Joist Erected into Place
Aligning Bar Joist
Bolting Ends of Bar Joist
Bolting Other End from X-Bracing
Figure A.11: CPM Schedule for the Bar Joist Erection
All five members were active during this cycle. Two different crew compositions were used in
different cycles. The first crew was composed of a ground crewman (making a five-man crew),
and the other crew omitted the ground crewman (making a four-man crew).
136
The individual task responsibilities for the bar joist cycle were broken down as follows. The
forklift operator was responsible for positioning bundles of bar joist under the crane hook,
attaching the first half of the x-bracing member on the ground and guiding the bar joist members
into the hands of the crewmen above. Table A.9 and Figure A.12 show the VA, NVA and NVAR
summary values of the forklift operator. During the bar joist cycle, the forklift operator was
involved in positioning the bar joist bundles under the crane hook to maximize the crane’s actions
in lifting the bar joists straight up, rather than having to swing the material from side to side. This
action was not included in the bar joist cycle times, though it was a required movement to enable
the cycle to start. The forklift operator contributed 25 percent of his total time to VA activities,
which involved bolting the first end of x-bracing to the bar joist while it remained on the ground.
The average time for this action was one minute and five seconds. Considerable time was also
spent on waiting and moving material. Waiting time was governed by the time it took the crane
to be freed from the previous bar joist.
Table A.9: Bar Joist Data for the Forklift Operator
Ac tivity C la ssific ation
VA
T otal T im e a t Ac tivity
V alu e Ad d in g
% of T otal T im e
0:26:07
25.22%
0:26 :07
2 5.2 2%
W aitin g
E xtra Pro c.
0:24:28
0:05:13
23.63%
5.04%
T ran sp o rt
0:12:48
12.36%
M o tio n
0:21:00
20.28%
1:03 :29
6 1.3 1%
0:03:58
0:01:30
0:08:29
3.83%
1.45%
8.19%
NV AR T otal
0:13 :57
1 3.4 7%
G rand T otal
1:43 :33
10 0.0 0%
V A T otal
NV A
NV A T ota l
NV AR
M at. Po s.
In -P ro cess-In s.
T .W .S .A.
Forklift Operator - Bar Joist Cycle
NVAR In-Process Inspections
1%
NVAR TWSA
8%
VA
26%
NVAR Material
Positioning
4%
NVA Motion
20%
NVA Waiting
24%
NVA Transport
12%
5%
Figure A.12: Bar Joist Data for the Forklift Operator
137
The ground crewman was responsible for guiding the bar joist members into the hands of the
crewmen above and positioning the x-bracing material next to the bar joist bundles to be attached
by the forklift operator. Table A.10 and Figure A.13 show the VA, NVA and NVAR summary
values for the ground crewman. The ground crewman did not complete any VA actions during
the bar joist cycles. It was further noted that the ground crewman was the least effective member
of the group. The forklift operator was more productive when the ground crewman was not
involved. In fact, when the ground crewman was absent, the forklift operator’s waiting time
decreased to almost nothing. This point is made clearer by the crew balance charts presented
later in this case study.
Table A.10: Bar Joist Data for the Ground Crewman
NVA
% of Total Time
0:22:31
0:02:00
40.45%
3.59%
0:24:31
44.04%
Mat. Pos.
0:10:05
18.11%
T.W.S.A.
0:21:04
37.84%
NVAR Total
0:31:09
55.96%
Grand Total
0:55:40
100.00%
Waiting
Transport
NVA Total
NVAR
Ground Crewman - Bar Joist Cycle
NVA Waiting
40%
NVAR TWSA
38%
NVA Transport
4%
NVAR Material
Positioning
18%
Figure A.13: Bar Joist Data for the Ground Crewman
138
The left connector was responsible for positioning and aligning the bar joist into its final position
on top of the girder. Bolting the bar joist to the girder below followed the positioning and
alignment process. Table A.11 and Figure A.14 show the VA, NVA and NVAR summary values
for the left connector.
Table A.11: Bar Joist Data for the Left Connector
VA
Value Adding
VA Total
% of Total Time
0:42:28
40.87%
0:42:28
40.87%
0:16:13
0:16:40
15.61%
16.04%
0:32:53
31.65%
NVA
Waiting
Motion
NVA Total
NVAR
0:28:33
27.48%
NVAR Total
Mat. Pos.
0:28:33
27.48%
Grand Total
1:43:54
100.00%
Left Connector - Bar Joist Cycle
NVAR Material
Positioning
27%
VA
41%
NVA Motion
16%
NVA Waiting
16%
Figure A.14: Bar Joist Data for the Left Connector
The right connector was responsible for positioning and aligning the bar joist into its final
position on the side opposite the left connector. Bolting the bar joist to the girder followed the
positioning and alignment process. Table A.12 and Figure A.15 show the VA, NVA and NVAR
results for the right connector. The right and left connectors had similar cycles. The only VA
action completed by the connectors involved bolting the bar joist to the girder. On average, the
left connector spent one minute 42 seconds on this task, and the right connector spent one minute
five seconds. Note that the right connector’s VA contribution was significantly less than that of
the left connector. Even with both workers’ contributions to VA actions, a considerable amount
of time was still spent on NVA activities. Another observation made concerning the left
139
connector was that he did not use the Genie lift provided for him. Had he done so, he would have
only needed to tie off one time. Instead, he preferred to walk the girder between joist placements
and tie off with two safety lines to the girder. This added to the total number of actions needed
for him to complete each bar joist cycle. Both workers spent an equal amount of time on NVA
activities.
Table A.12: Bar Joist Data for the Right Connector
VA
Value Adding
% of Total Time
0:29:21
26.09%
0:29:21
26.09%
0:30:42
0:24:55
27.29%
22.15%
0:55:37
49.44%
0:26:32
0:01:00
23.59%
0.89%
NVAR Total
0:27:32
24.47%
G rand Total
1:52:30
100.00%
VA Total
NVA
Waiting
Motion
NVA Total
NVAR
Mat. Pos.
T .W.S.A.
Right Connector - Bar Joist Cycle
NVAR TWSA
1%
NVAR Material
Positioning
24%
VA
26%
NVA Motion
22%
NVA Waiting
27%
Figure A.15: Bar Joist Data for the Right Connector
The x-bracing connector’s tasks included bolting the opposite end of the x-bracing member to the
adjacent, already in-place bar joist, and releasing the crane rigging from the bar joist member
after it was secured. Table A.13 and Figure A.16 show the VA, NVA and NVAR results for the
x-bracing connector.
140
Table A.13: Bar Joist Data for the X-Bracing Connector
VA
Value Adding
VA Total
% of Total Time
0:57:45
56.90%
0:57:45
56.90%
0:11:00
0:30:00
10.84%
29.56%
0:41:00
40.39%
NVA
Waiting
Motion
NVA Total
NVAR
0:02:45
2.71%
NVAR Total
T.W.S.A.
0:02:45
2.71%
Grand Total
1:41:30
100.00%
X-Bracing Connector - Bar Joist Cycle
NVAR TWSA
3%
NVA Motion
30%
VA
56%
NVA Waiting
11%
Figure A.16: Bar Joist Data for the X-Bracing Connector
The x-bracing connector’s job was a critical factor in the cycle because the crane was not allowed
to unhook from the bar joist until the x-bracing was bolted to the adjacent bar joist. This VA
action was more than 57 percent of the total time spent by the x-bracing connector during the bar
joist cycle. This worker also maneuvered the sky lift under each new bar joist as it was brought
up by the crane, which accounted for more than 30 percent of his time.
3.0 Results for the Crew: Crew Balance Charts
As previously mentioned, two different crew compositions were observed. To the casual
observer, the difference in crew makeup between the two crews was minimal. From a crew
141
balance perspective, however, the difference in efficiency/productivity was significant.
Figures A.17 and A.18 show the two balance charts for the separate crew structures. These charts
were compiled using the average times generated from the entire set of data observations. These
average times resulted in an “idealized” crew balance. Due to the lack of sufficient repetition of
the column and girder cycles, the crew balance charts were constructed using only the bar joist
data.
3.1 Crew Composition 1: With Ground Crewman
The crew balance chart on Figure A.17 includes the ground crewman data. Different shaded
sections within the chart represent the separate tasks for each worker. For example, the dotted
area represents a portion of the activity in which waiting occurred. The driver for this cycle was
the left connector.
Crew Balance With Ground Crewman
TIME
0:10:00
0:09:45
0:09:30
0:09:15
0:09:00
0:08:45
0:08:30
0:08:15
0:08:00
0:07:45
0:07:30
0:07:15
0:07:00
0:06:45
0:06:30
0:06:15
0:06:00
0:05:45
0:05:30
0:05:15
0:05:00
0:04:45
0:04:30
0:04:15
0:04:00
0:03:45
0:03:30
0:03:15
0:03:00
0:02:45
0:02:30
0:02:15
0:02:00
0:01:45
0:01:30
0:01:15
0:01:00
0:00:45
0:00:30
0:00:15
0:00:00
Waiting
Bolting X-Bracing
Bolting BJ
Waiting
Aligning BJ
Positioning BJ
Waiting
Aligning BJ
Hook Up Rigging
Move
Move
Move
Unhook Rigging
Hook Up Rigging
Waiting
Attach X-Bracing
Bolting BJ
Bolting BJ
Bolting BJ
Aligning BJ
Waiting
Aligning BJ
Waiting
Waiting
Move
Move
Move
Unhook Rigging
Positioning BJ
`
Hook Up Rigging
Hook Up Rigging
Waiting
Attach X-Bracing
Bolting BJ
Bolting BJ
Bolting BJ
Aligning BJ
Waiting
Aligning BJ
Waiting
Move
Move
Move
Unhook Rigging
Positioning BJ
Hook Up Rigging
Hook Up Rigging
Bolting BJ
Waiting
Bolting BJ
Bolting BJ
Ground Crewman
Left Connector
Aligning BJ
Right Connector
Attach X-Bracing
Forklift Operator
Figure A.17: Crew Balance Chart With Ground Crewman
142
Waiting
X-B Connector
Crew Balance
TIME
Waiting
Bolting X-Bracing
Bolting BJ
Positioning BJ
Aligning BJ
Waiting
Aligning BJ
Hook Up Rigging
Move
N o t In v o lv e d in P ro c e s s
0:10:00
0:09:45
0:09:30
0:09:15
0:09:00
0:08:45
0:08:30
0:08:15
0:08:00
0:07:45
0:07:30
0:07:15
0:07:00
0:06:45
0:06:30
0:06:15
0:06:00
0:05:45
0:05:30
0:05:15
0:05:00
0:04:45
0:04:30
0:04:15
0:04:00
0:03:45
0:03:30
0:03:15
0:03:00
0:02:45
0:02:30
0:02:15
0:02:00
0:01:45
0:01:30
0:01:15
0:01:00
0:00:45
0:00:30
0:00:15
0:00:00
Attach X-Bracing
Waiting
Positioning BJ
Hook Up Rigging
Attach X-Bracing
Waiting
Positioning BJ
Hook Up Rigging
Move
Move
Unhook Rigging
Bolting BJ
Bolting BJ
Bolting BJ
Aligning BJ
Aligning BJ
Waiting
Waiting
Move
Move
Move
Unhook Rigging
Bolting BJ
Bolting BJ
Bolting BJ
Aligning BJ
Aligning BJ
Waiting
Move
Move
Bolting BJ
Bolting BJ
Left Connector
Aligning BJ
Right Connector
Move
Unhook Rigging
Bolting BJ
Attach X-Bracing
Forklift Operator
Ground Crewman
Waiting
X-B Connector
Figure A.18: Crew Balance Chart Without Ground Crewman
This idealized balance chart shows that the left connector had no waiting time throughout the
multiple cycles. During a typical cycle, the forklift operator waited an average of one minute
15 seconds, and the ground crewman waited an average of two minutes. The rest of their time
was spent rigging the crane and attaching the x-bracing to the bar joist on the ground. As a result,
one third to one half of the crew time was wasted on waiting for the crane to be released on top.
It is important to note that this is an idealized crew balance using average task times. This ideal
cycle is typically shorter than the actual cycle time in which task time variability causes an
increase in the overall cycle time.
3.2 Crew Composition 2: Without Ground Crewman
On Figure A.18, it is immediately apparent that without the ground crewman, the forklift
operator’s idle time was reduced to 15 seconds. Also, he was able to accomplish the tasks of
143
attaching the x-bracing, hooking up the rigging for the crane and positioning the bar joist to those
above without delaying the cycle time. The left connector was still the driver (i.e., bottleneck
activity) for this cycle, and the other two workers (right connector and x-bracing connector) were
not affected at all by the reduction of the crew size from a five-man to a four-man crew. This
presents an opportunity to improve the overall cycle time by redesigning the left connector’s
work tasks and practices. The overall outcome shows that crew productivity can be increased by
this minor restructuring of the group.
3.3 General Observations about Crew Composition
During the column cycle, an observation was made that at least two of the five workers were
waiting throughout the entire cycle because the crew was too large for that activity. Again,
during the girder cycle, the majority of the five-member crew remained idle. A large portion of
this waiting was attributed to the difficulty that the right and left connectors had in setting the
girder connections. Most of the crew wasted roughly one-half hour because the girder
connections did not fit onto the knife plate connected to the column. As can be seen from the
previous tables, the variation between the different cycles of VA to NVA and/or NVAR
highlights the dilemma currently plaguing the construction industry. These findings demonstrate
that while a crew can be efficient for one cycle (e.g., the bar joist cycle), the same crew may not
be sized correctly for other activities on the jobsite.
4.0 Process Improvement Opportunities
A goal of this report was to examine and document the different forms of waste that occur in
construction operations. In general terms, inefficiencies were classified as the following three
types: inefficiency due to waste (NVA activities), inefficiency due to unnecessary work
(excessive NVAR activities) and inefficiency due to poorly designed work processes (ineffective
VA activities). The following section identifies opportunities for process improvement by
applying Ohno’s (Shingo and Dillon 1989) seven wastes in production and then evaluating the
production process against a more comprehensive set of lean principles.
Table A.14 shows the percentage of time spent on VA, NVA and NVAR as a percentage of total
cumulative time available to each worker for the entire work cycle observed. Table A.15 lists the
subset of activities that occurred to accomplish the entire erection process. In particular, the
NVA category is further divided into time spent in the waiting, extra processing, transport and
movement categories. Additionally, NVAR is broken down into its three subcategories to clarify
how time was spent within the observed cycles. The following analysis categorizes and describes
the various wastes viewed on the jobsite.
Table A.14: Entire Activity
VA
Crew Member
All
Activities
17%
Forklift Operator
0%
Ground Crewman
32%
Left Connector
38%
X-Bracing Connector
Right Connector
21%
Group Percentage
25%
11:27:10 h:m:s
NVAR
Material In-Process
Extra
Total
Waiting Processing Transport Movement Positioning Inspection TWSA
28%
3%
8%
18%
5%
2%
19%
100%
40%
0%
4%
0%
18%
0%
38%
100%
17%
11%
0%
16%
25%
0%
0%
100%
35%
0%
0%
23%
0%
0%
5%
100%
29%
12%
0%
17%
19%
0%
2%
100%
Waste
28%
6%
2%
144
17%
13%
0%
9%
100%
VA +
NVAR
43%
56%
57%
42%
42%
46%
Table A.15: Summary of Subactivities
Columns
Crew Member
Forklift Operator
Ground Crewman
Left Connector
X-Bracing Connector
Right Connector
Group Percentage
Girders
VA
Waste
All
Extra
Activities Waiting Processing Transport Movement
7%
14%
0%
0%
16%
0%
0%
0%
0%
0%
13%
40%
0%
0%
46%
0%
66%
0%
0%
34%
0%
53%
0%
0%
18%
6%
35%
0%
Forklift Operator
Ground Crewman
Left Connector
X-Bracing Connector
Right Connector
Group Percentage
Bar Joists
Crew Member
Forklift Operator
Ground Crewman
Left Connector
X-Bracing Connector
Right Connector
Group Percentage
26%
7%
2%
VA
Crew Member
0%
Material
Positioning
7%
0%
0%
0%
29%
NVAR
In-Process
Inspection
4%
0%
0%
0%
0%
Waste
46%
27%
0%
3%
Material
Positioning
6%
0%
27%
0%
0%
In-Process
Inspection
0%
0%
0%
0%
0%
9%
0%
VA
Waste
All
Extra
25%
24%
5%
12%
20%
0%
40%
0%
4%
0%
41%
16%
0%
0%
16%
57%
11%
0%
0%
30%
25%
27%
0%
0%
22%
32%
34%
4%
TWSA
52%
0%
0%
0%
0%
Total
100%
0%
100%
100%
100%
24%
100%
2:10:31 h:m:s
VA +
NVAR
70%
0%
13%
0%
29%
39%
NVAR
All
Extra
0%
66%
0%
3%
11%
0%
0%
0%
0%
0%
16%
12%
44%
0%
2%
0%
87%
0%
0%
1%
16%
24%
60%
0%
0%
8%
1:19:32 h:m:s
9%
13%
TWSA
14%
0%
0%
12%
0%
Total
100%
0%
100%
100%
100%
6%
100%
7:57:07 h:m:s
VA +
NVAR
21%
0%
42%
12%
16%
23%
Material
Positioning
4%
18%
27%
0%
24%
NVAR
In-Process
Inspection
1%
0%
0%
0%
0%
TWSA
8%
38%
0%
3%
2%
Total
100%
100%
100%
100%
100%
VA +
NVAR
39%
56%
68%
60%
51%
1%
5%
3%
100%
41%
4.1 Waste Associated with Laborers and Equipment
4.1.1 Waiting
Several incidences of waiting occurred throughout the observation period. Table A.15 shows for
the column, girder and bar joist cycles that 35, 46 and 34 percent, respectively, of cumulative
cycle time was attributed to waiting. Even with the highly repetitive actions of the bar joist
erection process, a quarter of the available work time was wasted on waiting. Waiting time for a
crew or equipment was highly dependent on the reliability of the work processes. If an individual
worker or work process is subject to variable completion times for the same task, it disrupts the
entire subsequent operation. Analyses of the variability of individual work tasks are presented in
subsequent sections of this report.
4.1.2 Waste of Motion
Wasted movement was observed every time the workers moved the sky lift or the ground crew
had to walk to retrieve material for the erection process. Since motion from one work location to
another was part of the construction process, the motion category needed to be divided into
wasted motion (i.e., unnecessary motion due to unsuitable process design) and NVA motion. The
percentage of total time wasted due to motion for the column, girder and bar joist cycles was 26,
3 and 13 percent, respectively. An additional analysis of motion segregated by NVAR and NVA
categories was conducted to illuminate this difficult area (refer to Appendix I).
145
4.1.3 Waste of Extra Processing (Rework)
The interpretation of this category included the use of defective materials delivered onsite that
required modification to be operable. During both girder erection cycles, the crew made site
adjustments to the manufactured connections. This rework accounted for more than 27 percent of
the time available for the girder connections.
4.1.4 Waste of Transportation
Few instances were observed in which material was rehandled. The forklift operator and ground
crewman were required to move bar joist bundles between the column lines. They also moved xbracing components next to the crane’s “pick point” to attach the x-bracing to the bar joist just
prior to being lifted. For the column, girder and bar joist cycles, the respective percentage of time
spent on material movement was 0, 0 and 9 percent.
4.2 Waste Associated with Materials
4.2.1 Overproduction (WIP)
Overproduction waste (meaning too much of a building is produced) is rare in construction. Most
construction reflects a “build to contract mentality” that requires a specific product(s) to be
produced. Work in Progress (WIP), on the other hand, is evident in construction but is dependent
on the activity level being viewed. At the process-specific level, WIP is seldom observed.
However, at the management level, each unfinished component of the production process
represents WIP. For this study, WIP was represented by the unfinished structure.
4.2.2 Inventory
Material deliveries were made twice to this project: once at the beginning of erection, and once
halfway through. On average, structural steel members were onsite for two weeks prior to
erection.
Also, in addition to the main steel members, there was an inventory of
bridging/stiffening material onsite to be used after the main structure was erected.
4.2.3 Defects
Defects are defined as errors or deficiencies in a finished product that require additional work on
the part of the original crew or a follow-up crew. A defective structural element (e.g., column,
girder, etc.) is an example of a defect (i.e., the material has been passed through the value stream
to the next workstation). Another example of a defect is included in the punch list process at the
end of a job. When a defect in the finished product is found at this stage, a separate follow-up
crew is activated to correct the defect. Hence, the defect is pushed onto the next workstation. No
waste associated with defects was observed.
5.0 Value Stream Analysis
The following paragraphs describe the current value stream map for this structural steel erection
process, beginning from the time the material was ordered and shipped from the manufacturer,
through the construction production process, and ending with the material in final position in the
facility. Figure A.19 is a simple flow diagram, with each box representing a point in time when
146
the material was touched, either to be moved or transformed into its next stage (phase) in the
construction life cycle.
Interior joist beams
members moved to
final staging area in
each bay
Manufacturer
Initial dropoff
Initial shakeout
Secondary shakeout of
different joist beams
and girder members
for each bay
Specific girders
and joist beams
moved to final
staging area for
each bay
Picked up
and
positioned
by forklift
Final
placement
by crane
Figure A.19: Material Flow Diagram
Information on delivery and handling of the steel members was obtained from the site foreman.
Once it arrived onsite, the basic flow of the steel was as follows:
•
Steel was delivered from the factory by truck:
−
Each load was handled for the first time by forklifts, and the entire load
was removed from the truck bed. This minimized the amount of time
that the truck was required to stay onsite.
−
The first loads were offloaded at, or near, their final staging position.
However, as more loads were delivered, they were required to be placed
in staging areas farther away until space became available for the
remaining bar joists to be placed in their final staging area.
−
The design called for several types of bar joists, roughly 40 different
shapes and sizes. After the initial unloading, the next step was to shake
out the bundles. The interior joist members (within each bay, there was a
series of joist beams that were identical in shape and size, which were
always placed in the interior portion of the bay) were bundled together
and could be picked up and dropped off in one move to their next staging
area under their designated bay section.
−
The remaining bar joist members required in each bay section were
broken out of their respective bundles, shaken out, and moved with all
other required bar joists in each respective bay. This act of shaking out
the bar joists introduced one more touch to the value stream and a
minimum of four touches by the forklift operator.
−
After the joists were placed in their respective staging areas, one of two
patterns was followed. The first pattern involved the crane moving the
girders, bar joists and columns from the staging position to their final
position in the structure. The second pattern involved an extra step for
some of the interior bar joists. Specific bar joist bundles were picked up
by the forklift and rotated 90 degrees to a point directly under their final
place in the structure, and then lifted one by one into position.
147
−
X-bracing members were pre-assembled prior to connection to the bar
joists. The two pieces of the x-bracing were delivered onsite and stacked
in the material yard. When the joist beams were ready to be installed,
this pile was then moved to another staging area next to the interior joist
beams.*
5.1 Case Study No. 1--Value Stream Map
For the value stream map analysis depicted on Figure A.20, three levels were needed to represent
both the material and labor components. Level One represents the major staging positions that
material must go through to reach its finished state. Each time material was moved or
transformed, a stage box is used to represent the process. Some of the stages include substages
(Level Two) to represent processes that occurred simultaneously. The individual crew
contributions to the value stream are represented on Level Three.
The value stream map shown on Figure A.20 was created using the information described in the
preceding section. Each major stage that the structural steel members went through is represented
on Level One. The steel went through two substages during Stage Two before it reached Stage
Three. Although these actions were not observed, the project superintendent confirmed that they
did occur. An estimate of five days total is shown for completion of Stage Two. Each substage
required 50 percent of the total time to accomplish Stage Two. The value stream ended once the
steel erection process reached the detailing and welding stage. Again, the limited observation
period prevented acquiring data about this stage for the entire steel erection process. Attention
was instead focused on the three substages required for Stage Three of the value stream. In
Levels Two and Three, the majority of time spent during the steel erection process was on the bar
joist erection phase. Note that even though the crew was sized specifically for this activity, more
than 60 percent of the time spent on erecting bar joists was NVA. The largest portion of VA
actions was also observed during this substage.
Table A.16 and Figure A.21 show the quick summary results for the work distribution values. Of
the 792 total workable hours committed to the steel erection process, only 161 of them were VA.
The least amount of time was spent on NVAR actions. This number is a little skewed because the
time contributed by the crane operator was not included in the work distribution values for VA,
NVAR and NVA. If his time had been included, a small drop in the VA value and a small
increase in the NVAR value would be evident. During the steel erection process, NVA actions
accounted for the majority of the time expended.
Finally, Figure A.22 and Table A.17 illustrate how the work distribution values changed and
grew throughout the process life cycle. The weighted average results found in Level Three of the
value stream map were used to calculate all of the VA, NVAR and NVA values (Table A.17). As
shown on Figure A.22, the cumulative NVA hours line grew the fastest compared to the other
work distribution values. The black vertical line indicates when the steel delivery and shakeout
processes finished and the steel erection process began. The slope change for the cumulative
workable hours line indicates that more crew members were introduced to the process. As seen
on the figure, the cumulative VA line finally started to grow.
*One idea was to have the cross bracing assembled by the steel manufacturer before it arrived onsite. The
contractor stated that it leaves activities like this to be completed onsite to provide activities for the workers
on inclement weather days.
148
Production Control
Every 1-3 days
Project Engineer
Triggering Event
Level One
Two Phases of Steel are Ordered
Percent Complete
Distribution of Time from VSM
Steel Supplier
Project Feedback
Daily
As Required
NVA Time
NVAR Time
1
VA Time
Work Time
Five Cumulative Days to Deliver Steel
O
OO
0
O
100
200
300
400
500
600
700
800
Man-Hours
Stage One - Steel is Offloaded in
Respective Bays
Days Required
Stage Two (A,B) - Steel Shakeout
Process
2
Days Required
Equipment involved:
Forklifts
Workers involved
Crew
WT
VA ( 0%)
NVAR (20%)
NVA (80%)
5
Days Required
Equipment involved:
2
Forklifts
32
0
6.4
25.6
1
Workers involved
Crew
WT
VA ( 0%)
NVAR (0%)
NVA (100%)
2
Inv
2
80
0
0
80
Stage Two (A) - Bar Joists
Bundles Are Shook Out
Days required
Days required
Equipment involved:
Forklifts
Forklifts
2
40
0
0
40
Columns
Forklift Operator
Level Three Ground Crewman
Left Connector
X-Bracing Con.
Right Connector
Group Percentage
Waiting
14%
0%
40%
66%
53%
Extra
Processing
0%
0%
0%
0%
0%
All Activities
7%
0%
13%
0%
0%
6%
35%
0%
NVA Sum
Transport
0%
0%
0%
0%
0%
0%
VA
Group Percentage
Waiting
66%
0%
12%
87%
24%
Extra
Processing
0%
0%
44%
0%
60%
8%
47%
27%
NVA =
VA
Movement
16%
0%
46%
34%
18%
26%
7%
Waste
Transport
3%
0%
0%
0%
0%
0%
Waiting
24%
40%
16%
11%
27%
Extra
Processing
5%
0%
0%
0%
0%
5
78.7
4.7
26.8
47.2
TWSA
52%
0%
0%
0%
0%
2%
24%
31%
34%
4%
NVA =
25%
9%
100%
34%
2:10:31 h:m:s
28%
6%
39%
NVAR
In-Process
Inspection
0%
0%
0%
0%
0%
TWSA
14%
0%
0%
12%
0%
Total
100%
0%
100%
100%
100%
VA +
NVAR
21%
0%
42%
12%
16%
3%
9%
0%
6%
101%
23%
15%
7:57:07 h:m:s
Movement
20%
0%
16%
30%
22%
13%
Material
Positioning
4%
18%
27%
0%
24%
NVAR
In-Process
Inspection
1%
0%
0%
0%
0%
1%
5%
NVAR =
Waste
TWSA
8%
38%
0%
3%
2%
Total
100%
100%
100%
100%
100%
VA +
NVAR
39%
56%
68%
60%
51%
3%
99%
40%
9%
11:27:10 h:m:s
Extra
Processing
3%
0%
11%
0%
12%
VA +
NVAR
70%
0%
13%
0%
29%
Material
Positioning
6%
0%
27%
0%
0%
60%
Waiting
28%
40%
17%
35%
29%
Total
100%
0%
100%
100%
100%
Movement
11%
0%
2%
1%
0%
Waste
Transport
8%
4%
0%
0%
0%
Movement
18%
0%
16%
23%
17%
Material
Positioning
5%
18%
25%
0%
19%
NVAR
In-Process
Inspection
2%
0%
0%
0%
0%
TWSA
19%
38%
0%
5%
2%
Total
100%
100%
100%
100%
100%
VA +
NVAR
43%
56%
57%
42%
42%
2%
17%
13%
0%
9%
100%
46%
Table represents the time distribution for each element viewed during the observation period.
Cumulative
Number of
Cycle Time for
Time for
Members
Each Element
Various
Observed
Installed
1:19:32
2
0:39:46
Total Cumulative Time for Two Columns
2:10:31
2
1:05:15
Total Cumulative Time for Two Girders
7:57:07
26
0:18:21
Total Time
11:27:10
% of Total Time Each
% of Total
Steel Element
Time
Requires
12%
5.8%
19%
9.5%
69%
2.7%
Figure A.20: Value Stream Map
149
3.2
Equipment involved:
Crane,
Two Skylifts,
4
Forklift
Workers involved:
Crew
5
WT=
129.2
VA ( 8%) =
10.3
NVAR (15%) =
19.4
NVA (77%) =
99.4
2
NVAR
In-Process
Inspection
4%
0%
0%
0%
0%
NVAR =
Transport
12%
4%
0%
0%
0%
Days required
1:19:32 h:m:s
Material
Positioning
7%
0%
0%
0%
29%
77%
All Activities
25%
0%
41%
57%
25%
VA
Crew Member
All Activities
Forklift Operator
17%
Ground Crewman
0%
Left Connector
32%
X-Bracing Con.
38%
Right Connector
21%
Group Percentage
40
0
0
40
Crew Member
Group Percentage
2
NVAR Sum
Bar Joists
Forklift Operator
Ground Crewman
Left Connector
X-Bracing Con.
Right Connector
Crane, Forklift
Workers involved:
Crew
WT=
VA ( 6%) =
NVAR (34%) =
NVA (60%) =
61%
All Activities
0%
0%
16%
0%
16%
Joist Girder is Erected
2.0
Crew Member
680
161
89
430
Equipment involved:
Waste
Girders
Forklift Operator
Ground Crewman
Left Connector
X-Bracing Con.
Right Connector
Days required
VA
Crew Member
Working Days
24 days
Working Time
792 man-hours
VA Total
161 man-hours
NVAR Total
95 man-hours
NVA Total
536 man-hours
5
Inventory Days
10
Note: These steps occur at the same time. Columns and
Girders are erected first but cannot be continued until the
inner supporting bar joist has been erected.
1
Workers involved:
Crew
WT
VA ( 0%)
NVAR (0%)
NVA (100%)
2 to 4
Columns Erected
2.5
Equipment involved:
1
**Graph shows the amount of man-hours attributed to each work category. VA time +
NVAR time + NVA time = Work Time
17.0
Equipment involved:
Forklift, crane,
skylifts
Workers involved
Crew
WT=
VA ( 6%, 8%, 31%)
NVAR (34%, 15%, 9%
NVA (60%, 77%, 60%
Stage Two (B) - Specific Bar Joists
and Girders Are Pulled From
2.5
Workers involved:
Crew
WT
VA ( 0%)
NVAR (0%)
NVA (100%)
Inv
8
2
Level Two
25%
22%
53%
Bar Joist installed Along
with X-Bracing Members
Days required
11.8
Equipment involved:
Crane,
Two Skylifts,
4
Forklift
Workers involved:
Crew
5
WT=
472
VA ( 31%) =
146
NVAR (9%) =
42
NVA (60%) =
283
Table A.16: Quick Summary of Steel Process
Working Days
24 days
Working Time
792 man-hours
VA Total
161 man-hours
NVAR Total
95 man-hours
NVA Total
536 man-hours
Distribution of Tim e from VSM
NVA Time
NVAR Time
1
VA Time
Work Time
0
100
200
300
400
500
600
700
800
Man-Hours
Figure A.21: Graphical Display for the Quick Summary Table
Work Distribution
1200
1000
Time (man-hours)
800
Cumulative Workable Hours
600
400
Cumulative VA Hours
Delivery and
Preparation
Process
Erection Process Is
Under Way
Cumulative NVAR Hours.
Cumulative NVA Hours
200
Note: the percentages used to
create this chart are the average
values from the work distribution
values found for the entire crew.
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
Calendar Days
Figure A.22: Work Distribution Life Cycle Graph
150
Table A.17: Spreadsheet of Values Used to Create Work Distribution Life Cycle Graph
Stage
Stage 1
Stage 1
Stage 2
Stage 2
Stage 2
Weekend
Weekend
Stage 2
Stage 2
Stage 3
Stage 3
Stage 3
Weekend
Weekend
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Weekend
Weekend
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Weekend
Weekend
Stage 3
Stage 3
Stage 3
Stage 3
Steel is shaken out
Steel is shaken out
Steel is shaken out
Weekend
Weekend
Steel is shaken out
Steel is shaken out
One crew erecting S.S. (Columns, Joist Girder and Bar Joists)
Weekend
Weekend
Weekend
Weekend
Weekend
Weekend
Day
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Monday
Tuesday
Wednesday
Thursday
Cumulative
Cumulative
Hours
Cumulative
Cumulative
NVAR
NVA Cumulative
VA
NVAR
NVA
VA Cumulative NVAR
Calendar Calendar Calendar Workable Workable Crew Worked Workable Workable
Hours
Hours NVA Hours
Hours Percentage Percentage Percentage Hours VA Hours Hours
Days
Available per Day Hours
Hours
Days
Days
Hours
1
16
16
1
1
2
8
16
16
0%
20%
80%
0
0
3.2
3.2
12.8
12.8
2
16
32
1
2
2
8
16
32
0%
20%
80%
0
0
3.2
6.4
12.8
25.6
3
16
48
1
3
2
8
16
48
0%
0%
100%
0
0
0
6.4
16
41.6
4
16
64
1
4
2
8
16
64
0%
0%
100%
0
0
0
6.4
16
57.6
5
16
80
1
5
2
8
16
80
0%
0%
100%
0
0
0
6.4
16
73.6
6
16
96
0
5
2
0
0
80
0%
0%
100%
0
0
0
6.4
0
73.6
7
16
112
0
5
2
0
0
80
0%
0%
100%
0
0
0
6.4
0
73.6
8
16
128
1
6
2
8
16
96
0%
0%
100%
0
0
0
6.4
16
89.6
9
16
144
1
7
2
8
16
112
0%
0%
100%
0
0
0
6.4
16
105.6
10
40
184
1
8
5
8
40
152
25%
22%
53%
10
10
8.8
15.2
21.2
126.8
11
40
224
1
9
5
8
40
192
25%
22%
53%
10
20
8.8
24
21.2
148
12
40
264
1
10
5
8
40
232
25%
22%
53%
10
30
8.8
32.8
21.2
169.2
13
40
304
0
10
5
0
0
232
25%
22%
53%
0
30
0
32.8
0
169.2
14
40
344
0
10
5
0
0
232
25%
22%
53%
0
30
0
32.8
0
169.2
15
40
384
1
11
5
8
40
272
25%
22%
53%
10
40
8.8
41.6
21.2
190.4
16
40
424
1
12
5
8
40
312
25%
22%
53%
10
50
8.8
50.4
21.2
211.6
17
40
464
1
13
5
8
40
352
25%
22%
53%
10
60
8.8
59.2
21.2
232.8
18
40
504
1
14
5
8
40
392
25%
22%
53%
10
70
8.8
68
21.2
254
19
40
544
1
15
5
8
40
432
25%
22%
53%
10
80
8.8
76.8
21.2
275.2
20
40
584
0
15
5
0
0
432
25%
22%
53%
0
80
0
76.8
0
275.2
21
40
624
0
15
5
0
0
432
25%
22%
53%
0
80
0
76.8
0
275.2
22
40
664
1
16
5
8
40
472
25%
22%
53%
10
90
8.8
85.6
21.2
296.4
23
40
704
1
17
5
8
40
512
25%
22%
53%
10
100
8.8
94.4
21.2
317.6
24
40
744
1
18
5
8
40
552
25%
22%
53%
10
110
8.8
103.2
21.2
338.8
25
40
784
1
19
5
8
40
592
25%
22%
53%
10
120
8.8
112
21.2
360
26
40
824
1
20
5
8
40
632
25%
22%
53%
10
130
8.8
120.8
21.2
381.2
27
40
864
0
20
5
0
0
632
25%
22%
53%
0
130
0
120.8
0
381.2
28
40
904
0
20
5
0
0
632
25%
22%
53%
0
130
0
120.8
0
381.2
29
40
944
1
21
5
8
40
672
25%
22%
53%
10
140
8.8
129.6
21.2
402.4
30
40
984
1
22
5
8
40
712
25%
22%
53%
10
150
8.8
138.4
21.2
423.6
31
40
1024
1
23
5
8
40
752
25%
22%
53%
10
160
8.8
147.2
21.2
444.8
32
40
1064
1
24
5
8
40
792
25%
22%
53%
10
170
8.8
156
21.2
466
151
Appendix B
Case Study No. 2 - Structural Steel
1.0 Overview
1.1 Project Goal
The purpose of this case study was to collect data to develop a value stream map for construction
processes. Observations were limited to structural steel erection. Field data was gathered on two
separate value streams. The first was the actual flow of the steel from the time it arrived on the
jobsite until it was erected into final position. The second value stream was the flow of worker
activities performed to erect the steel.
prepared data sheets (refer to the end of this case study to view these spreadsheets). Two
different erection crews were observed. The first erection crew consisted of the following six
workers: four laborers, a steel erection foreman and a crane operator. The second erection crew
consisted of the following five workers: three laborers, a steel erection foreman and a crane
operator. Each laborer, along with the crane operator, was monitored by one member of the data
collection team. The foreman was not observed because of his lack of physical involvement with
the erection cycle. Each observer was equipped with a stopwatch and a clipboard containing data
sheets. One digital video camera was positioned to record all actions during the erection
sequence. The video recordings were taken to provide a means to do a more detailed analysis of
the activities.
Data was recorded as the activities occurred. Each time a new task was started, an entry was
made on the data sheet. For example, an entry might indicate that a worker was rigging a bar
joist for the crane. The next entry might indicate that the worker was waiting until the crane
lowered its hook so the worker could attach the rigging to the hook. The elapsed time for each
task was recorded as well as the observers’ judgment regarding whether the task was value
adding (VA), non-value adding (NVA) or non-value adding but required (NVAR).
The site included roughly 1,700 acres plus additional 300 acres reserved for future development.
Several buildings will eventually occupy the site. The case study focused on an area in the largest
of these buildings. The structure was approximately one million square feet and, when viewed
from the plan view, resembled the shape of the letter “F.” The structure was composed of several
smaller bay sections that roughly measured 60 feet by 60 feet. Two bays were erected using one
crew. A second crew finished the activities dealing with erecting purlins on top of a completed
bay section. The subset of operations formed part of the overall sequence of steel erection. The
steel erection activities were preceded by the foundation work, which was succeeded (following
the purlin erection) by the installation of wind bracing, final alignment and bolting. The steel
erection activities were partially constrained by the fact that nearly half of the caissons, drilled
and poured, were off by more than six inches; the caissons were being replaced during the
observation period. This constraint had little impact on the efficiency in each observed bay of
152
steel erection activities. However, delayed installation of these caissons would cause unnecessary
equipment movement and other inefficiencies to steel erection activities after this observation
period.
2.0 Steel Erection Process
2.1 Erection Cycle No. 1
The steel erection process consisted of the following three separate cycles: column erection, joist
girder erection and truss erection. The following pictures illustrate the steps taken to erect the
steel.
Step 1: Beginning of
Process
Step 2: Girder, Column
and Truss Erected
Step 4: Crane Moves Back,
Erects Two Columns
Step 5: Crane Moves,
Erects Two Girders
Step 6: Trusses are
Erected on Both Sides
Step 7: Crane Moves,
Erects Trusses
153
Step 3: Exterior Column
and Girder Erected
The process started with a column erection along a bay section. The area observed focused on a
three by 26 bay section of the entire structure. A Manitoc 4100 crane was used for the steel
erection process. Ideally, the crane could reach three columns along the outside bay, as well as
setting all joist girders and trusses between the columns in one crane movement. During steel
delivery, the columns, girders and trusses were placed around the area of the bay in piles of “like”
members. A ground crewman or foreman then searched the respective piles to locate and draw
directional lines and a north arrow on each steel member. Numbers, originally marked by the
manufacturer on each of the steel members indicated their final location in the structure according
to the given plans. The foreman constructed the erection order on paper that the crane operator
followed. After two neighboring columns were erected, a joist girder was placed between the
columns. Once the columns and joist girders were placed in their final positions in the bay, the
interleaving trusses were installed in a repetitive process.
2.2 Erection Cycle No. 2 - Purlins
The purlin erection cycle consisted of one primary cycle. The diagram below illustrates the
erection methodology used during the purlin erection cycle:
Diagram Representing Purlin Erection Process
The process started after the erection of columns, girders and trusses was completed in three bay
sections. A Manitoc 4400 crane was used during the purlin erection cycle. The purlins were
delivered in large bundles next to the bays. No pre-shakeout was completed before delivery.
After the foreman located the purlins on the ground, they were lifted one by one into their
respective positions in the structure. The purlins were placed into their final locations starting
with the outer corner bay (relative to the position of the cranes) of the newly erected structure and
continuing across the back row of the structure. The process started again by filling the middle
row of the three bay sections, and finished with the inner row of bay sections.
The configuration of the building frame necessitated that the steel erection crew perform four
separate tasks. Each task required movement from task location to task location. Each task also
required different amounts of equipment and workers. Therefore, in contrast to a highly
repetitive manufacturing sequence, it was very difficult to design an erection sequence that had
the correct number of workers or equipment for each of the four separate tasks.
154
During the period of observation, the following steel members were installed:
•
Three columns.
•
Two joist girders.
•
Two trusses.
•
Twelve purlins.
In addition, the following equipment and crew structures were observed:
•
Four sky lifts (Genie lifts).
•
Two cranes (Manitoc 4100 and 4400).
•
One crane operator.
•
Eight to 10 crew personnel.
were developed for each worker and task. The tables and figures describe the time spent on VA,
NVA and NVAR actions in each cycle.
2.3 Observation of Steel Erection Process
2.3.1 Steel Erection Process - Cycle No. 1
In the following subsections, each worker is referred to by the position that he or she occupied
during the truss cycles. These references are used for the column and joist girder cycles to
maintain consistency throughout the analysis. (Refer to the end of this case study to review the
data sheets.)
2.3.1.1 Column Erection Cycle. The column erection cycle consisted of the following
tasks: preparing the column base, rigging the column for crane, guiding the column into place,
bolting the base of the column to the baseplate on the foundation and unhooking the rigging from
the column. Figure B.1 shows the major tasks required to complete the column installation. The
shaded areas are used to indicate that some tasks took longer to complete than others, and that
those tasks could occur simultaneously with other tasks. The shaded regions are not intended to
show actual task durations.
Column Erection
1
2
3
4
5
6
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Prepping Column Base
Column Lifted Into Place
Column Base Is Bolted Down
Plumb Columns
Note: Continual shipment of material to site.
Typically after girders are in
position between columns.
Figure B.1: Schedule for a Column Erection Cycle
155
All members of the crew were involved with the erection of the columns. The main participants
in the column cycles included connector 1, 2 and the ground crewman. The crane operator and
second ground crewman were also involved; however, all of their movements were NVA or
NVAR.
Connector 1 was responsible for preparing the anchor bolts, aligning and bolting the column to
the baseplate, and releasing the crane rigging after the bolting was complete. Table B.1 and
Figure B.2 show the VA, NVA and NVAR values for connector 1. During the column cycles,
connector 1 spent most of his time (46.61 percent) performing NVAR actions. The only VA
actions occurred while bolting the column to the baseplate.
Table B.1: Column Data for Connector 1
Ac tiv ity C la ss ific a tio n
VA
W a s te C la ssific a tio n
V alu e A d d in g
V A T o ta l
T im e a t Ac tiv ity
% o f T im e a t Ac tiv ity
0 :0 8:2 3
27 .49 %
0 :0 8 :2 3
2 7 .4 9 %
0 :0 1:3 7
0 :0 1:4 7
5.3 0%
5.8 5%
NVA
E xtra P ro c .
M o tio n
W aitin g
0 :0 4:3 0
14 .75 %
0 :0 7 :5 4
2 5 .9 0 %
0 :1 0:0 1
0 :0 4:1 2
32 .84 %
13 .77 %
N V AR T o ta l
0 :1 4 :1 3
4 6 .6 1 %
G ra n d T o ta l
0 :3 0 :3 0
100%
N V A T o ta l
N V AR
M at. P o s.
T .W .S .A .
Connector #1 Column Data
NVAR TWSA
14%
VA
27%
NVA Extra
Processing
5%
NVAR Material
Positioning
33%
NVA Motion
6%
NVA Waiting
15%
Figure B.2: Column - Connector 1
156
Connector 2 mirrored the actions of connector 1 for all tasks involved with the column cycles.
Table B.2 and Figure B.3 show the VA, NVA and NVAR values for connector 2. Again,
connector 2 time spent the largest amount of time on NVAR actions (47 percent).
Table B.2: Column Cycle - Connector 2
Activity C lassificatio n
VA
W aste C lassificatio n
T im e at Activity
% o f T o tal T im e
(b lan k)
0:08:23
0:08:23
27.49%
27.49%
E xtra P ro c.
M o tio n
W aitin g
0:01:37
0:01:47
0:04:30
0:07:54
5.30%
5.85%
14.75%
25.90%
E q u ip . R eq .
M at. P o s.
N V A R T o tal
0:04:12
0:10:01
0:14:13
13.77%
32.84%
46.61%
G ran d T o tal
0:30:30
100.00%
V A T o tal
NVA
N V A T o tal
NVAR
Connector #2 Column Data
NVAR TWSA
14%
VA
27%
NVA Extra
Processing
5%
NVAR Material
Positioning
33%
NVA Motion
6%
NVA Waiting
15%
Figure B.3: Column Cycle - Connector 2
Ground crewman 1 contributed his largest percentage of VA activities during the erection of the
steel columns. Table B.3 and Figure B.4 show the VA, NVA and NVAR values for ground
crewman 1. Thirty-seven percent of the time attributed by ground crewman 1 involved bolting
the column to the baseplate. Note that the largest amount of time was spent on the NVA action of
waiting. Ground crewman 1 was only a part of one column cycle. The rest of his time was spent
locating steel and assisting the foreman with the steel erection sequence.
157
Table B.3: Column Cycle - Ground Crewman 1
A c tiv ity C la s s ific a tio n
VA
W a s te C la s s ific a tio n
V a lu e A d d in g
T im e a t A c tiv ity
% o f T im e a t A c tiv ity
0 :0 4 :4 9
3 6 .8 2 %
0 :0 4 :4 9
3 6 .8 2 %
0 :0 1 :0 3
0 :0 5 :1 9
8 .0 3 %
4 0 .6 4 %
0 :0 6 :2 2
4 8 .6 6 %
0 :0 0 :3 4
0 :0 1 :2 0
4 .3 3 %
1 0 .1 9 %
N V A R T o ta l
0 :0 1 :5 4
1 4 .5 2 %
G ra n d T o ta l
0 :1 3 :0 5
100%
V A T o ta l
NVA
E x tra P ro c .
W a itin g
N V A T o ta l
NV AR
M a t. P o s .
T .W .S .A .
Ground Crewman #1 (White Shirt)
Column Data
NVAR TWSA
10%
NVAR Material
Positioning
4%
VA
37%
NVA Waiting
41%
8%
Figure B.4: Column Cycle - Ground Crewman 1
Ground crewman 2 was not involved in any VA tasks during the column erection cycles.
Table B.4 and Figure B.5 show the VA, NVA and NVAR values for ground crewman 2. The
majority of the crewman’s time was spent on the NVA action of waiting (53 percent). A minimal
amount of time was contributed to material positioning and equipment requirements.
158
Table B.4: Column Cycle - Ground Crewman 2
NVA
Time at Activity
Waiting
Extra Proc.
Transport
Motion
NVA Total
0:17:03
0:02:02
0:02:05
0:06:57
53.14%
6.34%
6%
21.66%
0:28:07
87.64%
NVAR
Mat. Pos.
0:02:10
6.75%
T.W.S.A.
0:01:48
5.61%
NVAR Total
0:03:58
12.36%
Grand Total
0:32:05
100%
Ground Crewman #2 (Orange Shirt)
Column Data
NVAR TWSA
6%
6%
NVAR Material
Positioning
7%
NVA Motion
22%
NVA Transport
6%
NVA Waiting
53%
Figure B.5: Column Cycle - Ground Crewman 2
The crane operator contributed no VA activities to the column erection cycle. Table B.5 and
Figure B.6 show the VA, NVA and NVAR values for the crane operator. The crane operator was
primarily involved with transporting columns from their lay-down area to their final position in
the structure. The transport action occurred after the column was “picked” from the lay-down
area to the point above the baseplate. After reaching the baseplate, the crane held the member in
a temporary bracing position until the bolts were sufficiently tightened. These actions contributed
to the NVAR value of 68.76 percent for the temporary work and support activities (TWSA)
category.
159
Table B.5: Column Cycle - Crane Operator
NVA
Time at Activity
Motion
Transport
Waiting
NVA Total
0:02:02
0:05:44
0:01:52
6.59%
19%
6.05%
0:09:38
31.24%
NVAR
0:21:12
68.76%
NVAR Total
T.W.S.A.
0:21:12
68.76%
Grand Total
0:30:50
100%
Crane Operator - Column Data
NVA Motion
7%
NVA Transport
19%
NVA Waiting
6%
NVAR TWSA
68%
Figure B.6: Column Cycle - Crane Operator
2.3.1.2 Girder Erection Cycle. The girder erection process included the following
subtasks: preparing the girder with rigging for the crane, guiding the girder into the hands of crew
members stationed at the top end of the columns, adjusting/hammering girders to fit into slots,
bolting the girders into place, and unhooking crane rigging from the girder. Figure B.7 shows the
major tasks required to complete the girder installation. The shaded areas are used to indicate
that some tasks took longer to complete than others, and that those tasks could occur
simultaneously with other tasks. The shaded regions are not intended to show actual task
durations.
Joist Girder Erection
1
2
3
4
5
6
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Three Columns Have Been Erected
Rigging Girder for Crane
Girder Erected Into Place
Aligning Girder
Bolting Girder Into Place
Plumb Structure (with Columns)
Occurs simultaneously with
column plumbing.
Figure B.7: Schedule for a Girder Erection
160
All five members of the crew were observed during the girder erection cycle. Data for the five
crew members is presented below.
Connector 1 spent the majority of his time aligning and securing the joist girder after it was lifted
into position by the crane operator. Table B.6 and Figure B.8 show the VA, NVA and NVAR
values for connector 1. Notice that a slightly larger percentage of time was spent on VA actions
during the joist girder cycle than was spent during the column cycle. The majority (27 percent) of
the NVA time was attributed to movement of the sky lift between upper and lower connections as
well as between opposite ends of the bay section where the girders were placed.
Table B.6: Joist Girder Cycle - Connector 1
Activity C lassification
VA
Value Add in g
T im e at Activity
% of T im e at Activity
0:12:18
34.18%
0:12:18
34.18%
0:09:34
0:03:35
26.59%
9.96%
0:13:09
36.54%
0:08:38
0:01:54
23.99%
5.28%
NV AR T otal
0:10:32
29.27%
G rand T otal
0:35:59
100%
V A T otal
NV A
M o tion
W aitin g
NV A T otal
NV AR
M at. P os.
T .W .S.A.
Connector #1 - Joist Girder Data
NVAR TWSA
5%
VA
34%
NVAR Material
Positioning
24%
NVA Waiting
10%
NVA Motion
27%
Figure B.8: Joist Girder Cycle - Connector 1
161
Connector 2 was also involved with aligning and bolting the joist girder after it was lifted into
position by the crane. Table B.7 and Figure B.9 show the VA, NVA and NVAR values for
connector 2. One point of interest between the two connectors was the jump in percentage of
time spent on NVA actions to 51 percent. A significant portion of time for connector 2 was spent
hammering and readjusting (extra processing) the girder to fit correctly. This extra processing
required connector 2 to move the sky lift around the girder connection accounting for the extra
time attributed to the NVA waste category of motion (36.35 percent).
Table B.7: Joist Girder Cycle - Connector 2
Ac tiv ity C la s s ific a tio n
VA
V a lu e A d d in g
V A T o ta l
0 :0 5 :4 8
1 5 .8 3 %
0 :0 5 :4 8
1 5 .8 3 %
0 :0 2 :3 7
0 :1 3 :1 9
7 .1 4 %
3 6 .3 5 %
NVA
E x tra P ro c .
M o tio n
W a itin g
0 :0 2 :4 3
7 .4 2 %
0 :1 8 :3 9
5 0 .9 1 %
0 :1 1 :3 9
0 :0 0 :3 2
3 1 .8 0 %
1 .4 6 %
N V AR T o ta l
0 :1 2 :1 1
3 3 .2 6 %
G ra n d T o ta l
0 :3 6 :3 8
100%
N V A T o ta l
N V AR
M a t. P o s .
T .W .S .A .
Connector #2 - Joist Girder Data
NVAR TWSA
1%
VA
16%
NVAR Material
Positioning
32%
7%
NVA Waiting
7%
NVA Motion
37%
Figure B.9: Joist Girder Cycle - Connector 2
Ground crewman 1 was responsible for locating individual members in the material yard, rigging
the girder for the crane and attaching a structural element used to support the edge of the building
parapet. Table B.8 and Figure B.10 show the VA, NVA and NVAR values for ground
crewman 1. The attachment of the parapet member accounted for the VA time (10 percent for the
crewman). The rest of the crewman’s time (90 percent) was attributed to NVA actions.
162
Table B.8: Joist Girder Cycle - Ground Crewman 1
VA
Value Adding
Time at Activity
0:01:53
10.13%
0:01:53
10.13%
Extra Proc.
Motion
0:08:58
0:03:53
48.25%
20.90%
Transport
0:01:47
10%
VA Total
NVA
0:02:04
11.12%
NVA Total
Waiting
0:16:42
89.87%
Grand Total
0:18:35
100%
Joist Girder Data
NVA Waiting
11%
VA
10%
NVA Transport
10%
NVA Motion
21%
48%
Figure B.10: Joist Girder Cycle - Ground Crewman 1
Ground crewman 2 was responsible for rigging each girder member for the crane with a tag line
to help position the girder into the hands of the connectors above. Table B.9 and Figure B.11
show the VA, NVA and NVAR values for ground crewman 2. Ground crewman 2 accomplished
no VA actions during the girder cycle. The largest portion of time (63 percent) was spent waiting
on other crew members.
163
Table B.9: Joist Girder Cycle - Ground Crewman 2
NVA
Motion
Transport
Waiting
NVA Total
Time at Activity
0:01:28
0:04:50
0:22:22
4.13%
14%
63.00%
0:28:40
80.75%
0:03:00
8.45%
NVAR
Mat. Pos.
0:03:50
10.80%
NVAR Total
T.W.S.A.
0:06:50
19.25%
Grand Total
0:35:30
100%
Joist Girder Data
NVAR TWSA
11%
NVA Motion
4%
NVA Transport
14%
NVAR Material
Positioning
8%
NVA Waiting
63%
Figure B.11: Joist Girder Cycle - Ground Crewman 2
The crane operator was responsible for lifting and positioning each member into final position in
the structure, as well as providing temporary support for those members during alignment and
bolting into place. Table B.10 and Figure B.12 show the VA, NVA and NVAR values for the
crane operator. Note that the majority of the crane operator’s time was spent on temporary
support activities (63 percent) while the connectors bolted each girder into place. This portion of
NVAR highlights an area in which the cost of crane operation time could be reduced. The time
attributed to transport included all movements of the girder after being lifted from the lay-down
yard until the crane was temporarily supporting the member in final position in the structure.
164
Table B.10: Crane Operator
NVA
Motion
Transport
Waiting
NVA Total
Time at Activity
0:03:08
0:02:41
0:01:17
8.60%
7%
3.52%
0:07:06
19.49%
NVAR
0:29:20
80.51%
NVAR Total
T.W.S.A.
0:29:20
80.51%
Grand Total
0:36:26
100%
Crane Operator - Joist Girder Data
NVA Motion
9%
NVA Transport
7%
NVA Waiting
4%
NVAR TWSA
80%
Figure B.12: Crane Operator
2.3.1.3 Truss Cycle. The truss cycle included the following subtasks: setting up the crane
rigging, positioning the truss into the hands of the connectors above, aligning and positioning the
truss into its final position on the structure, bolting the truss and releasing the crane rigging from
the truss. Figure B.13 shows the major tasks required to complete the truss installation. The
shaded areas are used to indicate that some tasks took longer to complete than others, and that
those tasks could occur simultaneously with other tasks. The shaded regions are not intended to
show actual task durations.
Truss Erection
1
2
3
4
5
6
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Two Columns and Two Girders Erected
Rigging Truss for Crane
Truss Erected Into Place
Aligning Truss
Bolting Ends of Truss
Purlins Erected After Bay Complete
Figure B.13: Schedule for Truss Erection
165
All five members of the crew were observed during the girder erection cycle. Data for the five
crew members is presented below.
Connector 1 was involved with aligning and positioning each truss member, bolting the end
connections and releasing the crane rigging after the connections were completed. Table B.11
and Figure B.14 show the VA, NVA and NVAR values for connector 1. Notice the large jump in
NVA time (62 percent) spent by the connector during the column and girder cycles. Connector 1
contributed the largest portion of his time to the NVA activities of waiting and wasted movement.
The waiting was due to the slow hookup for each member to the crane, along with the large swing
distance required for each pickup between the lay-down yard and the final position of the truss
member in the structure. Another notable observation was the amount of time wasted in motion,
or the movement of the sky lift between each truss (25 percent). Finally, despite the erection of
the truss being the most repetitive activity observed, it proved to be the largest contributor of
NVA activities of all cycles observed for this crewman.
Table B.11: Truss Cycle - Connector 1
VA
Value Adding
Time at Activity
0:03:44
12.17%
0:03:44
12.17%
0:07:40
0:11:25
24.99%
37.21%
0:19:05
62.19%
0:06:50
0:01:02
22.27%
3.37%
NVAR Total
0:07:52
25.64%
Grand Total
0:30:41
100%
VA Total
NVA
Motion
Waiting
NVA Total
NVAR
Mat. Pos.
T.W.S.A.
166
Connector #1 - Truss Data
NVAR TWSA
3%
VA
12%
NVAR Material
Positioning
22%
NVA Motion
25%
NVA Waiting
38%
Figure B.14: Truss Cycle - Connector 1
Connector 2 was involved with aligning and positioning each truss member, bolting the end
connections and releasing the crane rigging after the connections were completed. Table B.12
and Figure B.15 show the VA, NVA and NVAR values for connector 2. The NVA time spent by
the connector during all cycles remained the same, roughly 50 percent. Connector 2 contributed
the largest portion of his time to NVA activities. Time attributed to connecting the bolts was
nearly twice that of connector 1 for the truss cycle. The difference may be attributed to observer
discretion in determining when the individual tasks would start and stop. Finally, despite the
erection of the truss being the most repetitive activity observed, it proved to be the largest
contributor of NVA actions of all cycles observed for this crewman.
Table B.12: Truss Cycle - Connector 2
VA
Value Adding
VA Total
Time at Activity
0:07:40
25.46%
0:07:40
25.46%
0:00:49
0:06:06
2.71%
20.25%
NVA
Extra Proc.
Motion
Waiting
0:08:16
27.45%
0:15:11
50.42%
0:07:01
0:00:15
23.30%
0.83%
NVAR Total
0:07:16
24.13%
Grand Total
0:30:07
100%
NVA Total
NVAR
Mat. Pos.
T.W.S.A.
167
Connector #2- Truss Data
NVAR Material
Positioning
23%
NVAR TWSA
1%
VA
25%
NVA Extra
Processing
3%
NVA Waiting
28%
NVA Motion
20%
Figure B.15: Truss Cycle - Connector 2
Ground crewman 1 was responsible for locating and marking individual truss members with a
“north direction” arrow, rigging the truss for the crane and directing the crane operator for
material positioning. Table B.13 and Figure B.16 show the VA, NVA and NVAR values for
ground crewman 1. The largest percentage of time was attributed to NVA actions (96 percent),
mainly waiting around. Note that a smaller amount of time was observed for this worker. The
ground crewman left the observation area for the remainder of the observation time and,
therefore, was no longer contributing any action to the cycle.
Table B.13: Truss Cycle - Ground Crewman 1 - White Shirt
NVA
Extra Proc.
Motion
Waiting
Time at Activity
0:02:50
0:03:22
0:05:11
23.81%
28.29%
43.56%
0:11:23
95.66%
0:00:31
4.34%
NVAR Total
0:00:31
4.34%
Grand Total
0:11:54
100%
NVA Total
NVAR
Mat. Pos.
168
Truss Data
NVAR Material
Positioning
4%
24%
NVA Waiting
44%
NVA Motion
28%
Figure B.16: Truss Cycle - Ground Crewman 1
Ground crewman 2 was responsible for rigging each truss member for the crane and using a tag
line to position each truss into the hands of the connectors above. Table B.14 and Figure B.17
show the VA, NVA and NVAR values for ground crewman 2. The ground crewman
accomplished no VA actions during the truss erection. The largest portion of time was spent
waiting on the NVAR action of material positioning, roughly 67 percent. Notice that the amount
of time contributed by the ground crewman was smaller than the other crew members. This was
due to the ground crewman’s involvement in locating and rigging joist girders while the
remainder of the crew continued to work on the truss cycle.
Table B.14: Truss Cycle - Ground Crewman 2
NVA
Waiting
Time at Activity
0:02:59
32.55%
0:02:59
32.55%
0:05:46
0:00:25
62.91%
4.55%
NVAR Total
0:06:11
67.45%
Grand Total
0:09:10
100%
NVA Total
NVAR
Mat. Pos.
T.W.S.A.
169
Truss Data
NVAR TWSA
5%
NVA Waiting
33%
NVAR Material
Positioning
62%
Figure B.17: Truss Cycle - Ground Crewman 2
The crane operator was responsible for lifting and positioning each truss member into its final
position in the structure, and providing temporary support while each member was aligned and
bolted into place. Table B.15 and Figure B.18 show the VA, NVA and NVAR values for the
crane operator. Note that the majority of crane operator time was spent on temporary support
activities (73 percent) while the connectors aligned and bolted each truss into position. This
portion of NVAR highlights an area in which the cost of crane operation time could be reduced.
The time attributed to transport included all movements of the truss after being lifted from the
lay-down yard until the crane was holding/bracing the member in final position in the structure.
Table B.15: Truss Cycle - Crane Operator
NVA
Motion
Transport
Time at Activity
0:01:09
0:06:53
3.80%
23%
0:08:02
26.56%
0:22:13
73.44%
NVAR Total
0:22:13
73.44%
Grand Total
0:30:15
100%
NVA Total
NVAR
T.W.S.A.
170
Crane Operator - Truss Data
NVA Motion
4%
NVA Transport
23%
NVAR TWSA
73%
Figure B.18: Truss Cycle - Crane Operator
2.3.2 Purlin Erection Process - Cycle No. 2
Following the erection of the columns, girders and truss, the crew returned to each erected bay to
install the purlins. This cycle was completed before the distance of the farthest bay from the base
of the crane became too great for the crane to safely position the purlin on top of the trusses.
The data collected for the purlins involved a second crew; therefore, the referenced crew
members in the following sections do not correlate to the crew members referenced during steel
erection Cycle No. 1. In the following suibsections, each worker is referenced by the position
that he/she occupied during the purlin cycle. These referenced names were used to identify crew
members throughout the entire erection sequence. (Refer to the end of this case study to view
these data sheets.)
2.3.2.1 Purlin Cycle. Figure B.19 shows the schedule for purlin erection. The purlin cycle
included the following subtasks: setting up the crane rigging, positioning the purlin into the hands
of the connectors above, aligning and positioning the purlin into its final position on the structure,
bolting the truss and releasing the crane rigging from the truss.
Purlin Erection
1
2
3
4
5
6
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
One Bay Minimum Is Erected
Rigging Purlin for Crane
Purlin Erected Into Place
Aligning Purlin
Bolting Ends of Purlin
Entire Bay Is Plumbed and Welded
Figure B.19: Schedule for the Purlin Erection
Four crew members were observed during the purlin erection cycle. Data for the four crew
members is presented in the following paragraph.
171
Connector 1 was involved in aligning/positioning purlin members, bolting the end connections
and releasing the crane rigging after the connections were complete. Table B.16 and Figure B.20
show the VA, NVA and NVAR values for connector 1. Notice the large percentage of NVA time
(66 percent) that was wasted during the cycle. Connector 1 contributed the largest portion of his
time to the NVA subcategories of waiting and wasted movement (motion). Waiting was due to
the slow hookup for each purlin to the crane along with the large swing distance required for each
pick up between the lay-down yard and the final position of the purlin member in the structure.
Note the amount of time used just for motion, or the movement of the sky lift between each purlin
position (38 percent), which accounted for the largest portion of time consumed during the purlin
cycle.
Table B.16: Purlin Cycle - Connector 1
VA
T ime at Activity
% of T ime at Activitiy
Value Adding
0:02:20
0:02:20
5.86%
5.86%
Extra Proc.
Motion
Waiting
0:00:30
0:14:57
0:10:39
1.26%
37.55%
26.75%
0:26:06
65.55%
NVAR T otal
0:05:51
0:05:32
0:11:23
14.69%
13.90%
28.59%
Grand T otal
0:39:49
100.00%
VA T otal
NVA
NVA T otal
NVAR
Mat. Pos.
T .W.S.A.
Connector #1 - Purlin Data
NVAR
TWSA
14%
VA
6%
NVAR Material
Positioning
15%
NVA Extra
Processing
1%
NVA Motion
37%
NVA Waiting
27%
Figure B.20: Purlin Cycle - Connector 1
172
Connector 2 had similar responsibilities to those of connector 1. Table B.17 and Figure B.21
show the VA, NVA and NVAR values for Connector 2. The results for connector 2 are identical
to those of connector 1.
Table B.17: Purlin Cycle - Connector 2
VA
Time at Activity % of Time at Activitiy
Value Adding
0:05:00
0:05:00
12.56%
12.56%
Extra Proc.
Motion
Waiting
0:00:39
0:16:27
0:08:09
1.63%
41.31%
20.47%
0:25:15
63.42%
NVAR Total
0:06:51
0:02:43
0:09:34
17.20%
6.82%
24.03%
Grand Total
0:39:49
100.00%
VA Total
NVA
NVA Total
NVAR
Mat. Pos.
T.W.S.A.
Connector #2 - Purlin Data
NVAR Material
Positioning
17%
NVAR
TWSA
7%
VA
13%
NVA Extra
Processing
2%
NVA Motion
41%
NVA Waiting
20%
Figure B.21: Purlin Cycle - Connector 2
The ground crewman was responsible for locating and marking the individual purlin members
with a “north direction” arrow, rigging the purlin for the crane, using the tag line to position the
purlins into the hands of the connectors above, and directing the crane operator for material
positioning. Table B.18 and Figure B.22 show the VA, NVA and NVAR values for the ground
crewman. The largest percentage of time was attributed to NVA actions (63 percent), mainly
consisting of waiting around. There was a substantial amount of time spent on TWSA
(30 percent). Support activities for the crane required the worker to attach rigging for each
173
purlin. The time contributed to the motion category was due to the worker walking between
purlin locations on the ground.
Table B.18: Purlin Cycle - Ground Crewman
NVA
Motion
Transport
Waiting
0:05:04
0:01:15
0:19:02
0:25:21
12.61%
3.11%
47.37%
63.09%
Mat. Pos.
0:02:58
7.38%
T.W.S.A.
NVAR Total
0:11:52
0:14:50
29.53%
36.91%
Grand Total
0:40:11
100.00%
NVA Total
NVAR
Ground Crewman - Purlin Data
NVA Motion
13%
NVAR
TWSA
30%
NVA
Transport
3%
NVAR Material
Positioning
7%
NVA Waiting
47%
Figure B.22: Purlin Cycle - Ground Crewman
The crane operator was responsible for lifting and positioning each member into final position in
the structure and providing temporary support of those members during alignment and bolting
into place. Table B.19 and Figure B.23 show the VA, NVA and NVAR values for the crane
operator. The crane operator spent most of his time (41 percent) transporting each purlin from
the material lay-down area to the final position in the structure. Also, none of the crane operator
time was VA, which was to be expected since he never physically changed the shape of the
structure.
174
Table B.19: Purlin Cycle - Crane Operator
NVA
Motion
Transport
Waiting
0:07:02
0:16:25
0:07:59
0:31:26
17.58%
41.04%
19.96%
78.58%
T.W.S.A.
0:08:34
21.42%
NVAR Total
0:08:34
21.42%
Grand Total
0:40:00
100.00%
NVA Total
NVAR
Crane Operator - Purlin Data
NVAR
TWSA
21%
NVA Motion
18%
NVA Waiting
20%
NVA
Transport
41%
Figure B.23: Purlin Cycle - Crane Operator
As previously mentioned, two different crews were observed. The crew balance chart for the
structural steel erection (Cycle No. 1) is shown on Figure B.24. The crew balance for the purlin
erection cycle (Cycle No. 2) is shown on Figure B.25. These charts were compiled using the
average times generated from the entire set of data observations. These average times resulted in
an “idealized” crew balance. Due to the lack of sufficient repetition of the columns and girders,
the crew balance charts were developed using only the truss data for Cycle No. 1. A crew
balance chart was created for the purlin cycle as well.
175
Crew Balance - Truss Cycle
TIME
0:15:45
0:15:30
0:15:15
0:15:00
0:14:45
0:14:30
0:14:15
0:14:00
0:13:45
0:13:30
0:13:15
0:13:00
0:12:45
0:12:30
0:12:15
0:12:00
0:11:45
0:11:30
0:11:15
0:11:00
0:10:45
0:10:30
0:10:15
0:10:00
0:09:45
0:09:30
0:09:15
0:09:00
0:08:45
0:08:30
0:08:15
0:08:00
0:07:45
0:07:30
0:07:15
0:07:00
0:06:45
0:06:30
0:06:15
0:06:00
0:05:45
0:05:30
0:05:15
0:05:00
0:04:45
0:04:30
0:04:15
0:04:00
0:03:45
0:03:30
0:03:15
0:03:00
0:02:45
0:02:30
0:02:15
0:02:00
0:01:45
0:01:30
0:01:15
0:01:00
0:00:45
0:00:30
0:00:15
0:00:00
Swinging Truss to
Final Position
Waiting
Positioning Truss
w/ Tag Line
Preparing Truss
Locate Steel Piece
Waiting
Waiting
Truss Piece Attached
Hooking Up Tag Line
Swinging to Pick
Next Truss
Remove Truss
Rigging
Remove Truss
Rigging
Bolting Bottom
Connection
Waiting
Bolting Bottom
Connection
Waiting
Aligning Truss
Bottom Connection
Waiting
Waiting
Aligning Truss
Bottom Connection
Temporarily Supporting
Truss Member
Waiting
Move Lift
Waiting
Move Lift
Waiting
Bolting Top
Connection
Bolting Top
Connection
Waiting
Aligning Truss
Top Connection
Waiting
Waiting
Aligning Truss
Top Connection
Waiting
Waiting
Waiting
Waiting
Positioning Truss
Tag Line
Swinging Truss to
Final Position
Waiting
Waiting
Hooking Up Tag Line
Preparing Truss
Waiting
Truss Piece Attached
Waiting
Waiting
Locate Steel Piece
Ground Crewman #1
Ground Crewman #2
Note: Average times for each task were used to construct this chart.
Swinging to Pick
Next Truss
Crane Operator
Connector #1
Figure B.24: Crew Balance Chart - Cycle No. 1
176
Connector #2
Crew Balance - Purlins - Cycle No. 2
TIME
0:10:00
0:09:45
0:09:30
0:09:15
0:09:00
0:08:45
0:08:30
0:08:15
0:08:00
0:07:45
0:07:30
0:07:15
0:07:00
0:06:45
0:06:30
0:06:15
0:06:00
0:05:45
0:05:30
0:05:15
0:05:00
0:04:45
0:04:30
0:04:15
0:04:00
0:03:45
0:03:30
0:03:15
0:03:00
0:02:45
0:02:30
0:02:15
0:02:00
0:01:45
0:01:30
0:01:15
0:01:00
0:00:45
0:00:30
0:00:15
0:00:00
Set Up Rigging
for Purlin
Holding Piece in
Place to Be Bolted
Unhooking Rigging
Bolting Purlin
Bolting Purlin
Positioning Purlin
Positioning Purlin
Positioning Purlin
Waiting
Waiting
Lifting/Swinging
Purlin
from Material Yard
to Final Position in
Structure
Holding Tag Line
and Positioning
Waiting
Moving to
Next Purlin Position
Attaching Rigging
Holding for Hookup
Set Up Rigging
for Purlin
Holding Piece in
Place to Be Bolted
Unhooking Rigging
Bolting Purlin
Moving to
Unhooking Rigging
Bolting Purlin
Positioning Purlin
Positioning Purlin
Positioning Purlin
Waiting
Waiting
Lifting/Swinging
Purlin
from Material Yard
to Final Position in
Structure
Holding Tag Line
and Positioning
Waiting
Moving to
Attaching Rigging
Holding for Hookup
Set Up Rigging
for Purlin
Holding Piece in
Place to Be Bolted
Ground Crewman
Crane Operator
Note: Average times for each task were used to construct this chart.
Unhooking Rigging
Bolting Purlin
Positioning Purlin
Connector #1
Figure B.25: Crew Balance Chart - Cycle No. 2
177
Moving to
Unhooking Rigging
Bolting Purlin
Positioning Purlin
Connector #2
3.1 Crew Composition 1: Steel Erection (Cycle No. 1)
The crew balance chart on Figure B.24 compares the five crew members observed during the
truss cycle. Different shaded sections in the chart represent the separate tasks for each worker.
For example, the dotted area represents a portion of the activity in which waiting occurred. The
drivers for this cycle are connectors 1 and connector 2. The crane operator may appear to have
been the driver because he had no waiting time in his cycle. However, if the two connectors had
aligned the end connections at a faster rate, there would not have been much downtime for the
crane while it temporarily supported the truss in final position. The average time from each
activity was used to create a cycle duration. However, there was considerable variation between
the two truss cycles observed. One timed cycle was six minutes 45 seconds in duration, and the
other was 13 minutes 52 seconds. This kind of variability highlights an area where waste from an
activity could be reduced.
It is important to note that Figure B.24 represents an idealized crew balance using average task
times. This ideal cycle is typically shorter than the actual cycle time in which task time
variability causes an increase in the overall cycle time.
The average time it took the crane to lift a truss from the material lay-down area on the ground
and position it into final position in the structure, was two minutes 14 seconds. As noted on the
crew balance chart on Figure B.24, the majority of time for both ground crewmen was spent
waiting. The average waiting time during each cycle was three minutes 48 seconds for ground
crewman 1, and one minute two seconds for ground crewman 2.1
Waiting accounted for 25 percent of the total time contributed by the group to the truss cycle
(refer to the Table B.20 summary sheet for the entire truss cycle). The crew balance chart does
not account for individuals working on other cycles while the remainder of the crew completed
the truss cycle; therefore, in actuality the waiting periods shown for either ground crewman
represent time in which the workers could have been locating and preparing girders and/or
columns for their respective erection cycle.
3.2 Crew Composition 2: Purlin Erection (Cycle No. 2)
Figure B.25 shows the crew balance chart for the purlin erection cycle. The cycle time for each
purlin erection was significantly shorter than the cycle times observed for the truss erection. The
driver for this activity was the crane operator. The crane operator contributed a significant
portion of cycle time to transporting the purlins from the lay-down yard to their final position in
the structure. This waste indicated a possible problem with the organization in the material laydown yard. The existing material layout required the crane to be rotated nearly 180 degrees for
each pickup. For such a short cycle time, this material movement accounted for a large portion of
the cycle. By reducing the time required to move each purlin by roughly one minute 45 seconds,
the driver of the group then became connector 1, and the wasted time in waiting dropped to nearly
zero for the entire group.
1
Note that the discrepancy between the two members may have been due to observer error. The crew
balance chart is the idealized representation for the crew for erecting a truss. This ideal crew balance was
structured around the crane operator’s movements.
178
The average time that it took the crane to move a purlin from the material lay-down area on the
ground and position it into final position in the structure was one minute 12 seconds. The crew
balance chart, Figure B.25, shows that a large portion of time for the remaining crewmen was
wasted on waiting. The average waiting time during each cycle was 54 seconds for the ground
crewman; 58 seconds for connector 1; and 41 seconds for connector 2.1
Waiting accounted for 28.67 percent of the total time attributed by the crew members to the
erection of all purlins during this observation period. Refer to Table B.20 for the purlin cycle
waste percentage breakdown.
During the column cycle (Crew Composition 1), one ground crewman (No. 2) was observed
waiting through nearly the entire cycle because the crew was oversized for that activity. The time
attributed by ground crewman 1 during the column cycle was misleading because most of his
time was spent on activities in other cycles (e.g., preparation work for the girders and trusses
while the rest of the crew worked on columns). During the joist girder cycle, the majority of the
total time for ground crewman 2 was attributed to waiting, while ground crewman 1 focused the
majority of his time in extra processing activities. A large portion of waiting was attributed to
aligning the joist girder with the free-standing column (i.e., the column was not connected to any
other structural member at the time). The variations between the different cycles for VA, NVA
and NVAR actions highlight the difficulty of correctly sizing a crew for multiple activities on a
construction site.
applying Ohno’s (Shingo and Dillon, 1989) seven wastes in production and then evaluating the
Table B.20 shows a summary for each cycle as well as the average weighted values for both
cycles. Table B.21 lists the subset of activities that occurred to accomplish Cycle No. 1. Cycle
No. 2 did not have any subset activities. The NVA and NVAR categories were broken down to
clarify how time was spent in the observed cycles.
1
The crew balance chart is the idealized representation for the crew for erecting a purlin. This ideal crew
balance was structured around the crane operator’s movements, and the averages for each crew member
were used to best fit the cycle observed.
179
Table B.20: Entire Activity
Steel Erection - Column, Girder, Truss
VA
Crew Member
All Activities
Ground Crewman #1
15%
Ground Crewman #2
0%
Connector #1
25%
Connector #2
22%
Crane Operator #1
0%
Group Percentage
Steel Erection - Purlins
13%
Total Cumulative Time Observed for Entire Process
Total Cumulative Time Observed for Cycle 1
Waste
NVAR
Extra
Material
In Proc.
Waiting
Processing Transport Movement
Pos.
Ins.
29%
30%
4%
17%
2%
0%
55%
3%
9%
11%
14%
0%
20%
2%
0%
20%
26%
0%
16%
5%
0%
22%
29%
0%
3%
0%
16%
6%
0%
0%
23%
VA
Crew Member
Ground Crewman #3
Connector #3
Connector #4
Crane Operator #2
Group Percentage - Cycle 2
Weighted Average
Percentages for Group
5%
6%
15%
16%
Waste
Extra
Material
Pos.
0%
3%
13%
7%
1%
0%
38%
15%
2%
0%
41%
17%
0%
41%
18%
0%
0%
9:32:04 h:m:s
6:52:15 h:m:s
TWSA
3%
8%
7%
5%
75%
Total
100%
100%
100%
100%
100%
22%
100%
2:39:49 h:m:s
VA +
NVAR
21%
22%
59%
57%
75%
51%
NVAR
In Proc.
Ins.
0%
0%
0%
0%
TWSA
30%
14%
7%
21%
Total
100%
100%
100%
100%
VA +
NVAR
37%
34%
37%
21%
All Activities
0%
6%
13%
0%
Waiting
47%
27%
20%
20%
5%
29%
1%
11%
27%
10%
0%
18%
100%
32%
11%
24%
4%
7%
18%
14%
0%
21%
100%
46%
Table B.21: Summary of Subactivities
Columns
VA
Crew Member
Ground Crewman #1
Ground Crewman #2
Connector #1
Connector #2
Crane Operator #1
Group Percentage
Joist Girder
All Activities
37%
0%
27%
27%
0%
Waiting
41%
53%
15%
15%
6%
16%
24%
VA
Crew Member
Ground Crewman #1
Ground Crewman #2
Connector #1
Connector #2
Crane Operator #1
Group Percentage
Truss
All Activities
10%
0%
34%
16%
0%
Waiting
11%
63%
10%
7%
4%
12%
20%
VA
Crew Member
Ground Crewman #1
Ground Crewman #2
Connector #1
Connector #2
Crane Operator #1
Group Percentage
All Activities
0%
0%
12%
25%
0%
Waiting
44%
33%
37%
27%
0%
10%
25%
Total Cumulative Time Spent on Column
Waste
Extra
Material
Pos.
8%
0%
0%
4%
6%
6%
22%
7%
5%
0%
6%
33%
5%
0%
6%
33%
0%
19%
7%
69%
6%
9%
17%
5%
Total Cumulative Time Spent on Joist Girder
Waste
Extra
Material
Pos.
48%
10%
21%
0%
0%
14%
4%
8%
0%
0%
27%
24%
7%
0%
36%
32%
0%
7%
9%
0%
6%
19%
14%
7%
Total Cumulative Time Spent on Truss
Waste
Extra
Material
Pos.
24%
0%
28%
4%
0%
0%
0%
63%
0%
0%
25%
22%
3%
0%
20%
23%
0%
23%
4%
0%
3%
6%
180
16%
18%
2:17:00 h:m:s
NVAR
In Proc.
Ins.
0%
0%
0%
0%
0%
0%
NVAR
In Proc.
Ins.
0%
0%
0%
0%
0%
0%
TWSA
10%
6%
14%
14%
0%
Total
100%
100%
100%
100%
100%
24%
100%
2:43:08 h:m:s
TWSA
0%
11%
5%
1%
81%
Total
100%
100%
100%
100%
100%
22%
100%
1:52:07 h:m:s
VA +
NVAR
51%
12%
74%
74%
69%
56%
VA +
NVAR
10%
19%
63%
49%
81%
48%
NVAR
In Proc.
Ins.
0%
0%
0%
0%
0%
TWSA
0%
5%
3%
1%
73%
Total
100%
100%
100%
100%
100%
VA +
NVAR
4%
67%
38%
50%
73%
0%
21%
100%
49%
4.1.1 Waiting
Waiting accounted for roughly one quarter of the total time observed during each cycle shown in
Tables B.20 and B.21. The percentage of total time spent on waiting for the various cycles was
as follows:
•
Column cycle--24 percent.
•
Joist girder cycle--20 percent.
•
Truss cycle--25 percent.
In addition, the second crew spent 29 percent of its total time on waiting. For both crews, time
spent waiting was highly dependent on the structure of the crew and the task that the crew was
focused on during this observation period. For example, the column erection cycle required both
ground crewmen to help align and position the column on the baseplate. In contrast, the erection
of a truss may have only required one ground crewman to hold the tag line while positioning the
truss member into the hands of the connectors above.
For both crews, wasted motion occurred each time the sky lift was moved between truss, joist
girder and purlin members that were erected during each cycle. Wasted motion also occurred
each time the ground crew walked from point to point to locate material on the ground, or to
position themselves near the next structural member to be erected in the lay-down yard. Finally,
wasted movement occurred each time the crane swung from its holding position above the
structure to the material lay-down area, where each structural member was temporarily located.
The percentage of total time wasted due to motion for the column, joist girder, truss and purlin
cycles was nine, 19, 16 and 27 percent, respectively.
4.1.3 Waste of Extra Processing
Interpretation of this category included the use of defective materials delivered onsite that
required modification to be operable. This included any preparation work around connection
points such as cleaning out any metal slag that remained in the bolt holes from the manufacturer,
and any other preparation work required for the bolts prior to insertion into the bolt holes. During
truss and joist girder erection, the connection points were hammered to make the connections fit
together. For the column, joist girder, truss and purlin cycles, the respective percentage of time
spent on extra processing was five, seven, four and one percent.
Several instances were observed in which material was rehandled and moved into a more
accessible position for the installation process. Transportation absorbed a significant amount of
the crane operator’s time when moving each structural element from the lay-down yard to its
holding position above the structure. Other material transportation observations included the
ground crew carrying rigging from one steel piece to the next. Transport waste also occurred
181
when the material was positioned in the lay-down yard prior to the crane picking it up. However,
this waste could not be quantified due to a limited observation period.
4.2.1 Overproduction/Work in Progress (WIP)
produced. WIP, on the other hand, is evident in construction but is dependent on the activity
level being viewed. At the process-specific level, WIP is seldom observed. However, at the
management level, each unfinished component of the production process represents WIP. For
this study, WIP was represented by the unfinished structure.
4.2.2 Inventory/WIP
Material deliveries were made continually throughout the construction process. The steel was
delivered onsite on large flatbed trailers. It was observed sitting in the parking lot on top of
trailers (minus the cab) for several days until the steel was needed in the structure. The material
was moved into the lay-down area next to the structure, where it waited anywhere from one day
to two weeks before being erected in place. The variability of the amount of material onsite was
heavily influenced by the sporadic nature of the erection process. The caisson driller sustained
abnormally high numbers of rejected caisson placements, with several of the concrete caissons
being removed and replaced. The erection crew relocated several times to adjust to the caisson
problem.
4.2.3 Defects
to the next work station). Another example of defects is included in the punch list process at the
crew is activated to correct the defect. Hence, the defect is pushed onto the next work station.
No waste associated with defects was observed.
process, beginning from the time the material was ordered and shipped from the manufacturer,
facility. Figure B.26 is a simple flow diagram with each box representing a point in time when
the material was handled, either to be moved or transformed into the next stage (phase) in the
182
Manufacturer
stores
material
onsite in its
warehouse.
Material is
trucked to
site and
stored on
flatbeds until
needed.
Material is
trucked from
parking lot to
small material
lay-down area
near bay.
Steel is
offloaded by
a heavy-duty
forklift onto
the ground.
Each steel
member is
identified by a
ground
crewman and
north arrow
marked on it.
Final
placement
of steel
member
by crane.
Figure B.26: Material Flow Diagram
Information on delivery and handling of the steel joists was obtained from the project manager.
(Jackson 2003) Once it arrived onsite, the basic flow of the steel was as follows:
•
After the steel was manufactured, it remained onsite at the manufacturer’s
warehouse until needed.
•
Each steel shipment consisted of all structural steel members required in one bay.
Steel could not be stored onsite in a large material lay-down yard due to safety
restrictions. The steel for three to four bays was stored on truck trailers (minus
the cab) in the parking lot until needed. It usually remained in the parking lot for
one week before being handled again and moved to the second staging area - a
small material lay-down area next to the bay being erected.
•
Each load was handled by a heavy-duty forklift. Depending on the steel member
type, one to three separate lifting actions were needed by the forklift operator to
remove the entire load from the truck bed.
•
The load from the truck was placed on the ground in the same manner as it was
on the truck. No shakeout occurred from the truck to the ground.
•
The piles from the truck were organized by member type (columns with columns,
trusses with trusses, etc.).
•
Each steel member had a number that correlated to a number on the drawings.
Following the placement of each pile on the ground, a ground crewman located
the number on each steel piece and related it back to the foreman. This number
helped the erection crew foreman with the proper erection sequence.
•
No shakeout occurred after placement on the ground. The crane was required to
swing over the material lay-down area in random picks to reach each steel piece.
One piece was picked at a time. This created a large material transport time for
the crane operator.
•
After the steel members were placed near their respective bay staging areas, the
crane moved the girders, bar joists and columns from the staging position to final
position in the structure.
183
5.1 Case Study No. 2 Value Stream Map
For the value stream map analysis depicted on Figure B.27, three levels were needed to represent
material must go through to reach a finished state. Each time material was moved or transformed,
a stage box is used to represent the process. Some of the stages included substages (Level Two)
to represent processes that occurred simultaneously. The individual crew contributions to the
value stream are represented on Level Three.
Figures B.28, B.29 and B.30 show magnified views for each level introduced on Figure B.27.
For this case study, this value stream represents material and worker movements associated with
one crane. The project required three cranes of similar capacity to erect all the steel. The
weighted average values for each work distribution category represent input from two of the
construction teams. These values are assumed to be a reasonable representation for the entire
erection process on the project. The steel members initially went through three major stages,
which are represented on Level One. In Stage Two, each crane movement was observed; these
crane movements included substages required for the entire steel erection process. Notice that the
steel went through two stages before it reached Stage Three. Before the steel reached Stage One
it sat in the parking lot for an average of five days. This did not occur for all the steel; however,
the rule for inventorying was to represent the material piece in the order that it remained in one of
the “inventory” positions the longest period. This stage was not observed directly. However, it
was identified by the project superintendent as having occurred. The combined time period for
both Stages One and Two was one day. The value stream ended once the steel erection process
reached the detailing and welding stage. Again, the limited observation period prevented
acquiring data about this stage for the entire steel erection process. Attention was focused on the
four substages required for Stage Three of the value stream. In Levels Two and Three, the
majority of time spent during the steel erection process was on the truss erection phase. Even
though the crew was sized specifically for this activity, more than 50 percent of the time spent
erecting trusses was NVA! Many NVAR actions were also observed during this substage
process. The most significant contribution to the NVAR category was the crane operator being
required to temporarily hold the steel members in position while bolt-up occurred.
The most notable area for this value stream involved the multiple crane movements depicted in
Level One, Stage Three. Material was not organized around the worker in any particular fashion.
Instead, the crane was required to move several times in order to pick up a steel member,
transport it to its final position and then hold it in place while being bolted. Waste attributed to
waiting, transport and motion could be significantly reduced if the steel was delivered to the work
area in a more efficient manner.
Table B.22 shows the quick summary results for the work distribution values from Level One.
The value stream map depicts the flow of material and workers for one phase of the steel erection.
This is shown in the Quick Summary Table on the left-hand side. The right side of the table
shows the results for all 14 phases when complete. These values are found by multiplying the
results for one phase by 14. Figures B.31 and B.32 show the results for both sides of the Quick
Summary Table.
184
Production Control
Project Engineer
Every 1-3 days
Triggering Event
Distribution of Tme from VSM
For 14 Phases
Project Feedback
Percent Complete
Time Allocation
Field
14 Phases for the Steel Erection Process
Level One
NVA Time
NVAR Time
1
VA Time
Work Time
0
Steel Supplier
Daily
As Required
1500
2000
2500
Man-hours
OO
1000
For One Phase
All Steel for One Phase Is Ordered in One
Shipment (6 bays per order on avg.)
O
500
Steel In Place Awaiting Welding
O
NVA Time
NVAR Time
1
VA Time
Work Time
0
20
40
60
80
100
120
140
160
Man-hours
Stage One - Steel is moved from parking
lot to work area; has not been removed
Days required
0.5
Equipment involved:
Truck
Inv
Stage Two - Steel is offloaded in
bundles of like S.S. members.
Days required
0.5
Equipment involved:
1
Workers involved:
Crew
WT
VA ( 0%)
NVAR (0%)
NVA (100%)
Truck, forklifts
Workers involved:
Crew
WT
VA ( 0%)
NVAR (20%)
NVA (80%)
Inv
2
8
0
0
8
Material Waits on Trailers in
Parking Lot
5
2
16
0
3.2
12.8
0
4
Crane, two
skylifts
Workers involved:
Crew
WT
VA ( 25%, 12%)
NVAR (40%, 36%)
NVA (45%, 52)
Two Exterior columns erected
Days required
Equipment involved:
Crane, two skylifts
Workers involved:
Crew
Days required
Equipment involved:
Crane,
two skylifts
Workers involved:
Crew
WT
VA ( 12%)
NVAR (36%)
NVA (52%)
3
5
WT
VA ( 25%)
NVAR (41%)
NVA (44%)
7.3
1.1
2.9
3.2
Columns
VA
Crew Member
Level Three
Ground Crewman #1
Ground Crewman #2
Connector #1
Connector #2
Crane Operator #1
Group Percentage
All Activities
37%
0%
27%
27%
0%
16%
Waiting
41%
53%
15%
15%
6%
Days required
24%
5%
Crew Member
Group Percentage
All Activities
10%
0%
34%
16%
0%
Waiting
11%
63%
10%
7%
4%
12%
20%
14%
10%
25%
3%
6%
16%
18%
Waiting
47%
27%
20%
20%
5%
29%
50%
1%
13%
Waiting
29%
55%
20%
16%
3%
23%
VA
Crew Member
All Activities
0%
6%
13%
0%
Waiting
47%
27%
20%
20%
11%
27%
68%
10%
5%
6%
15%
16%
Waste
Extra
Processing
Transport
Movement
Material Pos.
0%
3%
13%
7%
1%
0%
38%
15%
2%
0%
41%
17%
0%
41%
18%
0%
5%
29%
1%
11%
24%
4%
3
2
2
12
Two Interior Girders erected
0.18
Days required
Equipment involved:
Crane,
two skylifts
Workers involved:
Crew
WT
VA ( 12%)
NVAR (36%)
NVA (52%)
3
5
7.3
1.1
2.9
3.2
0.32
3
5
13.0
1.6
4.7
6.7
2:17:00 h:m:s
NVAR
In Proc. Ins.
0%
0%
0%
0%
0%
T.W.S.A
10%
6%
14%
14%
0%
Total %
100%
100%
100%
100%
100%
VA + NVAR %
51%
12%
74%
74%
69%
0%
24%
100%
56%
2:43:08 h:m:s
NVAR
In Proc. Ins.
0%
0%
0%
0%
0%
T.W.S.A
0%
11%
5%
1%
81%
Total %
100%
100%
100%
100%
100%
VA + NVAR %
10%
19%
63%
49%
81%
0%
22%
100%
48%
36%
In Proc. Ins.
0%
0%
0%
0%
0%
T.W.S.A
0%
5%
3%
1%
73%
Total %
100%
100%
100%
100%
100%
VA + NVAR %
4%
67%
38%
50%
73%
0%
21%
100%
49%
39%
2:39:49 h:m:s
NVAR
In Proc. Ins.
0%
0%
0%
0%
T.W.S.A
30%
14%
7%
21%
Total %
100%
100%
100%
100%
VA + NVAR %
37%
34%
37%
21%
0%
18%
100%
32%
NVAR=
Waste
Extra
Processing
Transport
Movement
Material Pos.
30%
4%
17%
2%
3%
9%
11%
14%
2%
0%
20%
26%
5%
0%
22%
29%
0%
16%
6%
0%
Cumulative Time
Number of
for Various
Members
Cumulative Time for Each Element
Categories
Observed
2:17:00
Total Cumulative Time for Three Columns
2:43:08
1:52:07
Total Cumulative Time for Two Trusses
2:39:49
Total Cumulative Time for Twelve Purlins
Total Time
9:32:04
7.3
1.1
2.9
3.2
NVAR =
Waste
Extra
Processing
Transport
Movement
Material Pos.
0%
3%
13%
7%
1%
0%
38%
15%
2%
0%
41%
17%
0%
41%
18%
0%
NVA=
5
1:52:07 h:m:s
Material Pos.
4%
63%
22%
23%
0%
All Activities
0%
6%
13%
0%
Crane, two
skylifts
Workers involved:
Crew
WT
VA ( .12%,10%)
NVAR (36%,39%)
NVA (52%,51%)
3
NVAR
Movement
28%
0%
25%
20%
4%
28%
9:32:04 h:m:s
6:52:15 h:m:s
NVAR
In Proc. Ins.
0%
0%
0%
0%
0%
0%
For 14 Phases
56
2016 man-hours
181 man-hours
674 man-hours
1162 man-hours
Crane Movement #4
1.44
Days Required
T.W.S.A
3%
8%
7%
5%
75%
Total %
100%
100%
100%
100%
100%
22%
100%
2:39:49 h:m:s
VA + NVAR %
21%
22%
59%
57%
75%
51%
NVAR
In Proc. Ins.
0%
0%
0%
0%
T.W.S.A
30%
14%
7%
21%
Total %
100%
100%
100%
100%
VA + NVAR %
37%
34%
37%
21%
11%
27%
10%
0%
18%
100%
32%
7%
18%
14%
0%
21%
100%
46%
Cycle Time for
% of ETTRP
% of Observed Avg # of Elements Estimated Time to % of ETTRP for
% of Total
Each Element
Each Element Consumed by Each
Time Each Steel Within One Phase Erect All Elements
Time Observed
(6 Bays)
in a Phase
Installed
Category
Element in a Phase
Element Requires
0:45:40
24%
8%
8
6:05:20
12%
1.5%
1:21:34
29%
14%
8
10:52:32
22%
2.7%
0:56:03
20%
10%
30
4:01:45
56%
1.9%
0:13:19
28%
2%
24
5:19:38
11%
0.4%
50:19:15
Estimated Total Time Req. for One Phase (ETTRP)
11%
35%
54%
Figure B.27: Value Stream Map
185
0.87
Equipment involved:
Equipment involved:
NVAR =
Transport
0%
0%
0%
0%
23%
VA
Crew Member
All Activities
Ground Crewman #1
15%
Ground Crewman #2
0%
Connector #1
25%
Connector #2
22%
Crane Operator #1
0%
Weighted Average
19%
Extra
Processing
24%
0%
0%
3%
0%
Crew Member
Ground Crewman #3
Connector #3
Connector #4
Crane Operator #2
6%
52%
NVA =
Days required
41%
Waiting
44%
33%
37%
27%
0%
VA
Group Percentage
17%
VA Total
NVAR Total
NVA Total
Crane Movement #3
0.18
NVAR Sum
All Activities
0%
0%
12%
25%
0%
9%
Waste
Crew Member
Ground Crewman #3
Connector #3
Connector #4
Crane Operator #2
5
6%
7%
NVA =
VA
Group Percentage
3
13 man-hours
48 man-hours
83 man-hours
120.0
12.9
44.9
62.2
Inventory Days per
Phase
9
Two Interior columns erected
0.32
Waste
Extra
Processing
Transport
Movement
Material Pos.
48%
10%
21%
0%
0%
14%
4%
8%
0%
0%
27%
24%
7%
0%
36%
32%
0%
7%
9%
0%
Truss
Ground Crewman #1
Ground Crewman #2
Connector #1
Connector #2
Crane Operator #1
13.0
1.6
4.7
6.7
Days required
Equipment involved:
Crane,
two skylifts
Workers involved:
Crew
WT
VA ( 25%)
NVAR (41%)
NVA (44%)
5
44%
VA
Ground Crewman #1
Ground Crewman #2
Connector #1
Connector #2
Crane Operator #1
20.2
2.7
7.6
9.9
Crane, two
skylifts
Workers involved:
Crew
WT
VA ( .25%)
NVAR (40%)
NVA (45%)
3
Waste
Extra
Processing
Transport
Movement
Material Pos.
8%
0%
0%
4%
6%
6%
22%
7%
5%
0%
6%
33%
5%
0%
6%
33%
0%
19%
7%
69%
NVA Sum
Joist Girder
5
Equipment involved:
Two Exterior Girders erected
0.18
VA Total
NVAR Total
NVA Total
Crane Movement #2
0.51
Equipment involved:
Level Two
Workers involved:
Crew
WT
VA ( 11%)
NVAR (34%)
NVA (55%)
Inv
4
Crane Movement #1
Days required
For One Phase (3-6 bays)
Working Days
4
Working Days
Work Time
144 man-hours
Work Time
Stage Three - Structural steel erection
process.
Days required
3
Equipment involved:
Crane,
3
two skylifts
Crane,
two skylifts
Workers involved
Crew
WT
VA ( 10%)
NVAR (39%)
NVA (51%)
3
5
57.5
6.1
22.2
29.2
Exterior Bays - Trusses are
Erected
Days required
1.11
Equipment involved:
Crane,
3
two skylifts
Workers involved:
Crew
5
WT
44.6
VA ( 10%)
4.5
NVAR (39%)
17.5
NVA (51%)
22.5
3
5
35.0
2.9
12.2
19.9
Interior Bay - Trusses are Erected
Days Required
Equipment involved:
Crane,
two skylifts
Workers involved
Crew
WT
VA ( 10%)
NVAR (39%)
NVA (51%)
Purlin Installation Process
0.56
Days Required
Equipment involved:
3
Crane, 2 skylifts
5
22.3
2.3
8.8
11.2
Workers involved
Crew
WT
VA ( 5%)
NVAR (27%)
NVA (68%)
0.32
3
5
12.7
0.6
3.4
8.6
Production Control
Project Engineer
Level One
for 14 Phases
Project Feedback
Percent Complete
T im e A llo c a tio n
F ie ld
14 Phases for the Steel Erection Process
E v e ry 1 -3 d a y s
Triggering Event
NVA Time
NVAR Time
1
VA Time
Work Time
0
Steel Supplier
Daily
As Required
1500
2000
2500
Man-hours
T im e A llo c a tio n F ie ld
OO
1000
for One Phase
All Steel for One Phase Is Ordered in One
Shipment (6 bays per order on avg.)
O
500
Steel In Place Awaiting Welding
O
NVA Time
NVAR Time
1
VA Time
Work Time
0
20
40
60
80
100
120
140
160
Man-hours
Stage One - Steel is moved from
parking lot to work area; has not been
removed from trailers.
Days required
0.5
Equipment involved:
Truck
Inv
Material Waits on Trailers in
Parking Lot
5
Workers involved:
Crew
WT
VA ( 0%)
NVAR (0%)
NVA (100%)
Stage Two - Steel is offloaded in
bundles of like S.S. members.
1
Inv
2
8
0
0
8
0
Days required
Equipment involved:
Truck,
Forklifts
Workers involved:
Crew
WT
VA ( 0%)
NVAR (20%)
NVA (80%)
Stage Three - Structural steel erection
process.
0.5
2
Inv
4
16
0
3.2
12.8
4
Days required
3
Equipment involved:
Crane,
3
2 skylifts
Workers involved:
Crew
5
WT
0.0
VA ( 11%)
0.0
NVAR (34%)
0.0
NVA (55%)
0.0
Inventory Days per
Phase
9
Figure B.28: Level One
186
Working Days
4
Work Time
144 man-hours
Working Days
Work Time
VA Total
NVAR Total
NVA Total
VA Total
NVAR Total
NVA Total
13 man-hours
48 man-hours
83 man-hours
For 14 Phases
56
2016 man-hours
181 man-hours
674 man-hours
1162 man-hours
Level Two
Two Exterior
Columns Erected
Days
0.18
required
Equipment involved:
Crane,
two
3
skylifts
Workers involved:
Crew
5
WT
7.3
VA ( 25%)
1.1
2.9
NVAR (41%
3.2
NVA (44%)
Crane Movement #1
Crane Movement #2
Crane Movement #3
Crane Movement #4
Days
0.51
required
Equipment involved:
Crane,
two
3
skylifts
Workers involved:
Crew
5
WT
20.2
VA ( 25%,
2.7
7.6
NVAR (40%
9.9
NVA (45%,
Days
0.18
required
Equipment involved:
Crane,
two
3
skylifts
Workers involved:
Crew
5
WT
7.3
VA ( .25%)
1.1
NVAR (40%
2.9
NVA (45%)
3.2
Days
1.44
required
Equipment involved:
Crane,
two
3
skylifts
Workers involved:
Crew
5
WT
57.5
VA ( .12%,
6.1
NVAR (36%
22.2
NVA (52%,
29.2
Days
0.87
required
Equipment involved:
Crane,
two
3
skylifts
Workers involved:
Crew
5
WT
35.0
VA ( 10%)
2.9
NVAR (39%
12.2
NVA (51%)
19.9
Two Exterior Girders
Erected
Days
0.32
required
Equipment involved:
Crane,
two
3
skylifts
Workers involved:
Crew
5
WT
13.0
VA ( 12%)
1.6
NVAR (36%
4.7
NVA (52%)
6.7
Two Interior Columns
Erected
Days
0.18
required
Equipment involved:
Crane,
two
3
skylifts
Workers involved:
Crew
5
WT
7.3
VA ( 25%)
1.1
NVAR (41%
2.9
NVA (44%)
3.2
Two Interior Girders
Erected
Days
0.32
required
Equipment involved:
Crane,
two
3
skylifts
Workers involved:
Crew
5
WT
13.0
VA ( 12%)
1.6
NVAR (36%
4.7
NVA (52%)
6.7
Figure B.29: Level Two
187
Exterior Bays Trusses Are Erected
Days
1.11
required
Equipment involved:
Crane,
two
3
skylifts
Workers involved:
Crew
5
WT
44.6
VA ( 10%)
4.5
NVAR (39%
17.5
NVA (51%)
22.5
Interior Bay - Trusses
Are Erected
Days
0.56
required
Equipment involved:
Crane,
two
3
skylifts
Workers involved:
Crew
5
WT
22.3
VA ( 10%)
2.3
NVAR (39%
8.8
NVA (51%)
11.2
Purlin Installation
Process
Days
0.32
required
Equipment involved:
Crane,
two
3
skylifts
Workers involved:
Crew
5
WT
12.7
VA ( 5%)
0.6
NVAR (27%
3.4
NVA (68%)
8.6
Columns
VA
Crew Member
Level Three
Ground Crewman #1
Ground Crewman #2
Connector #1
Connector #2
Crane Operator #1
Group Percentage
All Activities
37%
0%
27%
27%
0%
16%
Waiting
41%
53%
15%
15%
6%
24%
Waste
Extra
Processing
Transport
Movement Material Pos.
8%
0%
0%
4%
6%
6%
22%
7%
5%
0%
6%
33%
5%
0%
6%
33%
0%
19%
7%
69%
VA
Group Percentage
All Activities
10%
0%
34%
16%
0%
Waiting
11%
63%
10%
7%
4%
12%
20%
7%
NVA =
100%
56%
19%
14%
2:43:08 h:m:s
NVAR
In-Proc. Ins.
0%
0%
0%
0%
0%
TWSA
0%
11%
5%
1%
81%
Total
100%
100%
100%
100%
100%
VA + NVAR
10%
19%
63%
49%
81%
0%
22%
100%
48%
NVAR =
36%
1:52:07 h:m:s
NVAR
Movement
28%
0%
25%
20%
4%
Material Pos.
4%
63%
22%
23%
0%
In-Proc. Ins.
0%
0%
0%
0%
0%
TWSA
0%
5%
3%
1%
73%
Total
100%
100%
100%
100%
100%
VA + NVAR
4%
67%
38%
50%
73%
10%
25%
3%
6%
16%
18%
0%
21%
100%
49%
All Activities
0%
6%
13%
0%
Waiting
47%
27%
20%
20%
5%
29%
50%
VA
Crew Member
All Activities
Ground Crewman #1
15%
Ground Crewman #2
0%
Connector #1
25%
Connector #2
22%
Crane Operator #1
0%
1%
13%
Waiting
29%
55%
20%
16%
3%
23%
VA
Crew Member
NVAR =
Waste
Extra
Processing
Transport
0%
3%
13%
7%
1%
0%
38%
15%
2%
0%
41%
17%
0%
41%
18%
0%
NVA=
Weighted Average
24%
Transport
0%
0%
0%
0%
23%
VA
Ground Crewman #3
Connector #3
Connector #4
Crane Operator #2
0%
Extra
Processing
24%
0%
0%
3%
0%
Crew Member
Group Percentage
VA + NVAR
51%
12%
74%
74%
69%
Waiting
44%
33%
37%
27%
0%
NVA =
Total
100%
100%
100%
100%
100%
All Activities
0%
0%
12%
25%
0%
Ground Crewman #3
Connector #3
Connector #4
Crane Operator #2
6%
52%
VA
TWSA
10%
6%
14%
14%
0%
41%
Waste
Crew Member
Group Percentage
17%
In-Proc. Ins.
0%
0%
0%
0%
0%
NVAR Sum
Waste
Extra
Processing
Transport
48%
10%
21%
0%
0%
14%
4%
8%
0%
0%
27%
24%
7%
0%
36%
32%
0%
7%
9%
0%
Truss
Ground Crewman #1
Ground Crewman #2
Connector #1
Connector #2
Crane Operator #1
9%
44%
Crew Member
Ground Crewman #1
Ground Crewman #2
Connector #1
Connector #2
Crane Operator #1
6%
5%
NVA Sum
Joist Girder
2:17:00 h:m:s
NVAR
11%
27%
68%
10%
39%
2:39:49 h:m:s
NVAR
In-Proc. Ins.
0%
0%
0%
0%
TWSA
30%
14%
7%
21%
Total
100%
100%
100%
100%
VA + NVAR
37%
34%
37%
21%
0%
18%
100%
32%
NVAR=
Waste
Extra
Processing
Transport
30%
4%
17%
2%
3%
9%
11%
14%
2%
0%
20%
26%
5%
0%
22%
29%
0%
16%
6%
0%
5%
6%
15%
16%
Waste
Extra
Processing
Transport
0%
3%
13%
7%
1%
0%
38%
15%
2%
0%
41%
17%
0%
41%
18%
0%
28%
9:32:04 h:m:s
6:52:15 h:m:s
NVAR
In-Proc. Ins.
0%
0%
0%
0%
0%
0%
TWSA
3%
8%
7%
5%
75%
Total
100%
100%
100%
100%
100%
22%
100%
2:39:49 h:m:s
VA + NVAR
21%
22%
59%
57%
75%
51%
NVAR
Total
100%
100%
100%
100%
VA + NVAR
37%
34%
37%
21%
All Activities
0%
6%
13%
0%
Waiting
47%
27%
20%
20%
5%
29%
1%
11%
27%
10%
0%
18%
100%
32%
11%
24%
4%
7%
18%
14%
0%
21%
100%
46%
In-Proc. Ins.
0%
0%
0%
0%
TWSA
30%
14%
7%
21%
% of Observed Avg # of Elements Estimated Time to % of ETTRP for
% of ETTRP
Cumulative Time
Number of
Cycle Time for
% of Total
Time Each Steel Within One Phase Erect All Elements Each Element Consumed by Each
for Various
Members
Each Element
Time Observed
Element Requires
Element in a Phase
Categories
Observed
Installed
(6 Bays)
in a Phase
Category
Total Cumulative Time for Three Columns
2:17:00
3
0:45:40
24
8
8
6:05:20
12
1.5
2:43:08
2
1:21:34
29
14
8
10:52:32
22
2.7
Total Cumulative Time for Two Trusses
1:52:07
2
0:56:03
20
10
30
4:01:45
56
1.9
2:39:49
12
0:13:19
28
2
24
5:19:38
11
0.4
Total Cumulative Time for Twelve Purlins
Total Time
9:32:04
50:19:15
Estimated Total Time Req. for One Phase (ETTRP)
Figure B.30: Level Three
188
11%
35%
54%
Table B.22
Quick Summary of Steel Process
Working Days
4
Working Days
Work Time
144 man-hours
Work Time
VA Total
13 man-hours
VA Total
NVAR Total
48 man-hours
NVAR Total
NVA Total
83 man-hours
NVA Total
For 14 Phases
56
2016
181
674
1162
man-hours
man-hours
man-hours
man-hours
Distribution of Tim e from VSM
for One Phase
NVA Time
NVAR Time
1
VA Time
Work Time
0
20
40
60
80
100
120
140
160
Man-hours
Figure B.31: Quick Summary Table - One Phase of the Steel Process
T im e A llo catio n
F ield
Distribution of Tme from VSM
for 14 Phases
NVA Time
NVAR Time
1
VA Time
Work Time
0
500
1000
1500
2000
Man-hours
Figure B.32: Quick Summary - 14 Phases of the Steel Process
189
2500
Of the 2,016 total workable hours committed to the steel erection process by this crew, only 181
of them were VA. Notice also that the greatest amount of time was spent on NVA actions
(1,162 man-hours). A significant amount of the NVAR time was from the crane operator. This
number could be reduced significantly if the erection processes were streamlined, e.g., by
reducing the amount of waiting by each crew member. When just one phase in the cycle is
considered, the numbers do not stand out as much when compared to the entire process. The fact
that more than half of the man-hours contributed on the job were in the form of waste highlights
an area needing vast improvement.
Figure B.33 and Table B.23 illustrate how the work distribution values changed and grew
throughout the process life cycle. The weighted average results found in Level Three of the value
stream map were used to formulate all the VA, NVAR and NVA values in Table B.23. As shown
on Figure B.33, the cumulative NVA line increased the fastest compared to the other work
distribution values. The black vertical line indicates when the steel delivery and shakeout
processes finished and the steel erection process began. This occurred periodically throughout
the life cycle. The slope change in the cumulative calendar hours line resulted from additional
workers periodically being added to the team to position each new phase of steel in front of the
erection crew. This crew variation affected the data results for the remaining lines shown on
Figure B.33. Material did not require multiple touches before erection. However, because the
material was not organized on the ground in any systematic fashion, this disorganization resulted
in larger values in the waste categories of motion and transportation for the erection crew.
Work Distribution
3000
2500
Time (man-hours)
2000
Cumulative VA Hours
1500
Cumulative NVAR Hours.
Marks Finishing
Point of Initial
Delivery
1000
500
Note: the values used to create
this chart are the average values
from the Work Distribution values
found for the entire crew.
0
1
3
5
7
9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59
Calendar Days
Figure B.33: Work Distribution Life Cycle Graph
190
Table B.23: Spreadsheet of Values Used to Create Work Distribution Life Cycle Graph
Stage
Stage 1,2 Steel is moved to work area and offloaded for next phase
Stage 3 One crew erecting S.S. (Columns, Joist Girder, Bar Joists and Purlins)
One crew erecting S.S. (Columns, Joist Girder, Bar Joists and Purlins);
Stage 1,2,3 steel is moved to work area and offloaded for next phase
Stage 3 Weekend
Stage 3 Weekend
Stage 3 Weekend
Stage 3 Weekend
Stage 3 Weekend
Stage 3 Weekend
Stage 3 Weekend
Stage 3 Weekend
Stage 3 Weekend
Stage 3 Weekend
Stage 3 Weekend
Stage 3 Weekend
Stage 3 Weekend
Stage 3 Weekend
Stage 3 Weekend
Stage 3 Weekend
Stage 3 Two crews erecting S.S. (Columns, Joist Girder and Bar Joists)
Calendar
Day
Days
Monday
1
Tuesday
1
Wednesday
1
Cumulative
Calendar
Days
1
2
3
Calendar
Hours
32
40
40
Cumulative
Cumulative
Hours
Calendar Workable Workable
Crew
Worked
Hours
Days
Days
Available Per Day
32
1
1
4
8
72
1
2
5
8
112
1
3
5
8
Workable Cumulative
VA
NVAR
NVA
VA
Cumulative
Hours Work Hours Percentage Percentage Percentage Hours VA Hours
32
32
0%
20%
80%
0
0
40
72
11%
35%
54%
4.4
4.4
40
112
11%
35%
54%
4.4
8.8
NVAR
Hours
6.4
14
14
Cumulative
NVAR
Hours
6.4
20.4
34.4
NVA
Hours
25.6
21.6
21.6
Cumulative
NVA Hours
25.6
47.2
68.8
Thursday
Friday
Saturday
Sunday
Monday
1
1
1
1
1
4
5
6
7
8
72
40
40
40
40
184
224
264
304
344
1
1
0
0
1
4
5
5
5
6
9
5
5
5
5
8
8
0
0
8
72
40
0
0
40
184
224
224
224
264
11%
11%
11%
11%
11%
35%
35%
35%
35%
35%
54%
54%
54%
54%
54%
7.92
4.4
0
0
4.4
16.72
21.12
21.12
21.12
25.52
25.2
14
0
0
14
59.6
73.6
73.6
73.6
87.6
38.88
21.6
0
0
21.6
107.68
129.28
129.28
129.28
150.88
Tuesday
Wednesday
Thursday
1
1
1
9
10
11
72
40
40
416
456
496
1
1
1
7
8
9
9
5
5
8
8
8
72
40
40
336
376
416
11%
11%
11%
35%
35%
35%
54%
54%
54%
7.92
4.4
4.4
33.44
37.84
42.24
25.2
14
14
112.8
126.8
140.8
38.88
21.6
21.6
189.76
211.36
232.96
Friday
Saturday
Sunday
Monday
Tuesday
1
1
1
1
1
12
13
14
15
16
72
40
40
40
40
568
608
648
688
728
1
0
0
1
1
10
10
10
11
12
9
5
5
5
5
8
0
0
8
8
72
0
0
40
40
488
488
488
528
568
11%
11%
11%
11%
11%
35%
35%
35%
35%
35%
54%
54%
54%
54%
54%
7.92
0
0
4.4
4.4
50.16
50.16
50.16
54.56
58.96
25.2
0
0
14
14
166
166
166
180
194
38.88
0
0
21.6
21.6
271.84
271.84
271.84
293.44
315.04
Wednesday
Thursday
Friday
Saturday
Sunday
1
1
1
1
1
17
18
19
20
21
72
40
40
40
40
800
840
880
920
960
1
1
1
0
0
13
14
15
15
15
9
5
5
5
5
8
8
8
0
0
72
40
40
0
0
640
680
720
720
720
11%
11%
11%
11%
11%
35%
35%
35%
35%
35%
54%
54%
54%
54%
54%
7.92
4.4
4.4
0
0
66.88
71.28
75.68
75.68
75.68
25.2
14
14
0
0
219.2
233.2
247.2
247.2
247.2
38.88
21.6
21.6
0
0
353.92
375.52
397.12
397.12
397.12
Monday
Tuesday
Wednesday
1
1
1
22
23
24
72
40
40
1032
1072
1112
1
1
1
16
17
18
9
5
5
8
8
8
72
40
40
792
832
872
11%
11%
11%
35%
35%
35%
54%
54%
54%
7.92
4.4
4.4
83.6
88
92.4
25.2
14
14
272.4
286.4
300.4
38.88
21.6
21.6
436
457.6
479.2
Thursday
Friday
Saturday
Sunday
Monday
1
1
1
1
1
25
26
27
28
29
72
40
40
40
40
1184
1224
1264
1304
1344
1
1
0
0
1
19
20
20
20
21
9
5
5
5
5
8
8
0
0
8
72
40
0
0
40
944
984
984
984
1024
11%
11%
11%
11%
11%
35%
35%
35%
35%
35%
54%
54%
54%
54%
54%
7.92
4.4
0
0
4.4
100.32
104.72
104.72
104.72
109.12
25.2
14
0
0
14
325.6
339.6
339.6
339.6
353.6
38.88
21.6
0
0
21.6
518.08
539.68
539.68
539.68
561.28
Tuesday
Wednesday
Thursday
1
1
1
30
31
32
72
40
40
1416
1456
1496
1
1
1
22
23
24
9
5
5
8
8
8
72
40
40
1096
1136
1176
11%
11%
11%
35%
35%
35%
54%
54%
54%
7.92
4.4
4.4
117.04
121.44
125.84
25.2
14
14
378.8
392.8
406.8
38.88
21.6
21.6
600.16
621.76
643.36
Friday
Saturday
Sunday
Monday
Tuesday
1
1
1
1
1
33
34
35
36
37
72
40
40
40
40
1568
1608
1648
1688
1728
1
0
0
1
1
25
25
25
26
27
9
5
5
5
5
8
0
0
8
8
72
0
0
40
40
1248
1248
1248
1288
1328
11%
11%
11%
11%
11%
35%
35%
35%
35%
35%
54%
54%
54%
54%
54%
7.92
0
0
4.4
4.4
133.76
133.76
133.76
138.16
142.56
25.2
0
0
14
14
432
432
432
446
460
38.88
0
0
21.6
21.6
682.24
682.24
682.24
703.84
725.44
Wednesday
Thursday
Friday
Saturday
Sunday
1
1
1
1
1
38
39
40
41
42
72
40
40
40
40
1800
1840
1880
1920
1960
1
1
1
0
0
28
29
30
30
30
9
5
5
5
5
8
8
8
0
0
72
40
40
0
0
1400
1440
1480
1480
1480
11%
11%
11%
11%
11%
35%
35%
35%
35%
35%
54%
54%
54%
54%
54%
7.92
4.4
4.4
0
0
150.48
154.88
159.28
159.28
159.28
25.2
14
14
0
0
485.2
499.2
513.2
513.2
513.2
38.88
21.6
21.6
0
0
764.32
785.92
807.52
807.52
807.52
Monday
Tuesday
Wednesday
1
1
1
43
44
45
72
40
40
2032
2072
2112
1
1
1
31
32
33
9
5
5
8
8
8
72
40
40
1552
1592
1632
11%
11%
11%
35%
35%
35%
54%
54%
54%
7.92
4.4
4.4
167.2
171.6
176
25.2
14
14
538.4
552.4
566.4
38.88
21.6
21.6
846.4
868
889.6
Thursday
Friday
Saturday
Sunday
Monday
1
1
1
1
1
46
47
48
49
50
72
40
40
40
40
2184
2224
2264
2304
2344
1
1
0
0
1
34
35
35
35
36
9
5
5
5
5
8
8
0
0
8
72
40
0
0
40
1704
1744
1744
1744
1784
11%
11%
11%
11%
11%
35%
35%
35%
35%
35%
54%
54%
54%
54%
54%
7.92
4.4
0
0
4.4
183.92
188.32
188.32
188.32
192.72
25.2
14
0
0
14
591.6
605.6
605.6
605.6
619.6
38.88
21.6
0
0
21.6
928.48
950.08
950.08
950.08
971.68
Tuesday
Wednesday
Thursday
1
1
1
51
52
53
72
40
40
2416
2456
2496
1
1
1
37
38
39
9
5
5
8
8
8
72
40
40
1856
1896
1936
11%
11%
11%
35%
35%
35%
54%
54%
54%
7.92
4.4
4.4
200.64
205.04
209.44
25.2
14
14
644.8
658.8
672.8
38.88
21.6
21.6
1010.56
1032.16
1053.76
Friday
Saturday
Sunday
Monday
Tuesday
Wednesday
1
1
1
1
1
1
54
55
56
57
58
59
72
40
40
40
40
72
2568
2608
2648
2688
2728
2800
1
0
0
1
1
1
40
40
40
41
42
43
9
5
5
5
5
9
8
0
0
8
8
8
72
0
0
40
40
72
2008
2008
2008
2048
2088
2160
11%
11%
11%
11%
11%
11%
35%
35%
35%
35%
35%
35%
54%
54%
54%
54%
54%
54%
7.92
0
0
4.4
4.4
7.92
217.36
217.36
217.36
221.76
226.16
234.08
25.2
0
0
14
14
25.2
698
698
698
712
726
751.2
38.88
0
0
21.6
21.6
38.88
1092.64
1092.64
1092.64
1114.24
1135.84
1174.72
191
11%
35%
54%
Appendix C
Case Study No. 3 - Structural Steel
1.0 Overview
1.1 Project Goal
construction process. Observation was limited to structural steel erection. Field data were
gathered on two separate value streams: the actual flow of the steel from the time it arrived on
the jobsite until it was erected into final position, and the flow of worker activities performed to
erect the steel.
prepared data sheets (refer to the end of this case study to view these spreadsheets). Two
different erection crews were observed. The first erection crew consisted of the following five
workers: two ground crewmen, a foreman, one connector, and a crane operator. The second
erection crew consisted of the following seven workers: two ground crewmen, two (end)
connectors, two x-bracing connectors and a crane operator. Each observer was equipped with a
digital camera. The digital video cameras were positioned to view the activity area at right angles
to provide “depth” in both viewing directions.
In the lab, two televisions were placed next to each other and used to view the recorded steel
erection process. Using both cameras provide a three-dimensional view of the workspace for the
data collection process. Each time a new task was started, an entry was made on the data sheet.
For example, an entry might indicate that a worker was positioning a bar joist member. The next
entry might indicate that the worker was bolting the end connection to the girder beneath. The
elapsed time for each task was recorded as well as the observer’s judgment regarding whether the
task was value adding (VA), non-value adding (NVA) or non-value adding but required (NVAR).
Three main structures were erected at this site. The case study focused on an area within the
largest building. The total square footage for all buildings erected on this site was approximately
1.3 million. The observation period focused on the largest structure, which accounted for more
than half of the total constructible square footage onsite. The structure was composed of several
smaller bay sections, roughly measuring 60 feet by 60 feet. The observed erection activities for
one crew occurred within four new bays, with a focus on columns, pod beam and spandrel beam
erection. The second follow-up crew was observed handling the erection activities for bar joist
members. The subset of the observed operations form part of the overall sequence of steel
erection. The steel erection activities were preceded by foundation work, which was succeeded
(following purlin erection) by the installation of wind bracing, final alignment and finish bolting.
There were no visible constraints for the erection crews during this observation period; however,
it was noted that an unfinished foundation wall along the north side of the structure will affect
future erection sequences. The steel erection crews will not be able to erect the structure to the
192
end column line and will be required to return after the foundation pour to erect the remaining
steel members. This future constraint had no impact on the efficiency within each bay of steel
erection activities.
2.0 Steel Erection Work Process
The steel erection process consists of the following two separate cycles: column erection and pod
beam combo (PBC) erection. A PBC consists of a spandrel beam and a pod beam that are bolted
together before Crew No. 1 takes the steel and erects it into position. Figure C.1 shows an
elevation view of this configuration with the PBC in its final position on top of a column.
Bolted Connection
Spandrel Beam
Pod Beam
Column
Figure C.1: Elevation View of a PBC on Top of a Column
The following figures illustrate the erection cycle available for each movement of the crane.
Figure C.2 shows a column and PBC already erected by Crew No. 1.
Figure C.3 shows Crew No. 1 erecting the next column and PBC, while Crew No. 2 follows
behind erecting the bar joists. This same process is followed for each new bay Crew No. 1 leads,
while Crew No. 2 follows.
Bar Joists
Crew No. 2
PBC
Crew No. 1
Column
Figure C.3: Column, PBC and Bar Joists
Erected
Figure C.2: Column and PBC Erected
193
2.1 Erection Cycle No. 1 - Column, Spandrel Beam and Pod
Beam Erection
Cycle No. 1 focused on the erection of one column and one PBC per crane movement. Four
iterations of this cycle occurred during this observation period. The cycle began when the crane
operator lifted the column into position on top of the baseplate. Two ground crewmen and the
foreman aligned and bolted the column to the baseplate. The choker was then removed from the
crane ball. Beam clamps and tag lines (cable lines) were attached to the PBC, which was then
lifted by the crane into final position. The connector used the sky lift to bolt the extruding
spandrel beam section from the PBC to the adjacent PBC. The connector then moved with the
sky lift to the top of the newly erected column and bolted the pod beam base to the top of the
column. From there, the ground crewmen secured tag lines to an anchor device on either side of
the column to temporarily support the member until the interconnecting bar joist was erected. For
safety reasons, the crew could erect only two columns and PBCs ahead of the bar joist crew
(Crew No. 2). Continuing with the cycle, the beam clamps were released from the PBC and the
crane and crew moved to the next column line to continue the erection process. The cycle ended
at the point chosen by the crane operator for the next column; then, the cycle was repeated.
2.2 Erection Cycle No. 2 - Bar Joists
The bar joist erection cycle consisted of one main task, erecting the bar joist member. Twentyfour bar joist members were observed waiting to be erected. Twelve members were erected per
crane movement. The process started after four columns and two PBCs were erected within a 60
foot by 60 foot bay. A second 30 ton crane was used during the bar joist erection cycle. The bar
joist cycle began as ground crewman 3 attached an x-bracing member to a bar joist member while
it was on the ground. Each bar joist was then lifted and positioned into place on top of the
supporting roof beams (pod beam and spandrel beam). The members were bolted down on each
end while the remaining sections of the x-bracing member were bolted into place. The crane was
then released to pick up the next bar joist from the ground. After 12 bar joists were erected, the
crane was moved to the next bay to continue the erection process.
The configuration of the building frame necessitated that the steel erection crews perform four
separate tasks. The bolting of each spandrel beam to a pod beam on the ground was not observed,
but was included as one of the four tasks. Each task required movement from location to another
and also required different amounts of equipment and workers. Therefore, in contrast to a highly
repetitive manufacturing sequence, it was difficult to design an erection sequence that had the
correct number of workers or equipment for each of the four separate tasks.
During this observation period, the following materials were installed:
•
Four columns.
•
Four spandrel beams.
•
Four pod beams.
•
24 bar joists.
194
•
−
Two sky lifts.
−
Two cranes.
−
Two crane operators.
−
12 crew personnel.
were developed for each worker and for each task. The tables and figures describe the time spent
on VA, NVA and NVAR actions within each cycle.
2.3 Steel Erection Process - Cycle No. 1
In the following subsections, each worker is referred to by the position that he/she occupied
during the column and PBC erection sequence. These references are used to maintain
consistency throughout the analysis. (Refer to the end of this case study to review the data
sheets.)
The cycle consisted of the following tasks: rigging the column for the crane, lifting the column
into place, positioning the column, bolting the base of the column to the baseplate, unhooking the
rigging from the column, attaching beam clamps to the PBC, lifting the PBC, positioning the
PBC into place, bolting the PBC to adjacent PBC, bolting pod beam base to top of column,
releasing beam clamps and moving to the next column line. Figure C.4 shows the major tasks
required to complete the column installation. The shaded areas are used to visually indicate that
some tasks took longer to complete than others, and that those tasks could occur simultaneously
with other tasks. The shaded regions are not intended to show actual task durations.
Column and Pod Beam Combo
Erection
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Column Lifted Into Place
Positioning Column On Base
Column Base Is Bolted Down
Beam Clamps Attached to PBC
PBC Is Lifted Into Place
Positioning PBC Into Place
Bolting to Adjacent PBC
Bolting to Column
Releasing Beam Clamps
Moving to Next Column Line
Figure C.4: Schedule for a Column-PBC Erection Cycle
The following analysis details the two structural members (column and PBC) separately to show
how a crew may be sized efficiently for one structural member but over/undersized for another.
Notice also the actual amount of time contributed to the cycle by each crew member. While a
crew member may have a large VA value for his or her result, the total time attributed by that
crew member to the cycle may be minuscule compared to other crew members.
195
2.3.1 Column Erection Cycle
All members of the crew were involved with the column erections. The main participants in the
column cycles included ground crewmen 1 and 2, the crew foreman, the connector and the crane
operator.
Ground crewman 1 was responsible for positioning the column, bolting the column to the
baseplate and releasing the crane rigging after the bolting was complete. Table C.1 and
Figure C.5 show the VA, NVA and NVAR values for ground crewman 1. During the column
cycles, ground crewman 1 spent most of his time (45.10 percent) performing NVAR actions. The
only VA actions occurred while he was bolting the column to the baseplate.
Table C.1: Column Data for Ground Crewman 1
VA
Value Adding
VA Total
% of Total Time
0:00:50
16.34%
0:00:50
16.34%
NVA
Waiting
0:01:58
38.56%
0:01:58
38.56%
0:01:30
0:00:48
29.41%
15.69%
NVAR Total
0:02:18
45.10%
Grand Total
0:05:06
100.00%
NVA Total
NVAR
Mat. Pos
T.W.S.A.
Ground Crewman #1
Column Data
NVAR
TWSA
16%
VA
16%
NVAR Material
Positioning
29%
NVA Waiting
39%
Figure C.5: Column Data for Ground Crewman 1
196
Ground crewman 2 rigged the column with a choker, positioned the column, bolted the column to
the baseplate and released the choker from the crane once the column was set. Table C.2 and
Figure C.6 show the VA, NVA and NVAR values for ground crewman 2. The time spent by
ground crewman 2 on the column was more than what ground crewman 1 spent. In Table C.2, a
large portion of time was spent on NVA actions, specifically on NVA waiting (32.76 percent).
The different results of the two ground crewmen were due to ground crewman 2 spending more
time on column activities.
Table C.2: Column Data for Ground Crewman 2
VA
T o ta l T im e a t A c tiv ity
V a lu e A d d in g
% o f T o ta l T im e
0 :0 5 :1 1
1 9 .9 0 %
0 :0 5 :1 1
1 9 .9 0 %
W a itin g
0 :0 8 :3 2
3 2 .7 6 %
T ra n s p o rt
0 :0 2 :3 0
9 .6 0 %
M o tio n
0 :0 2 :4 6
1 0 .6 2 %
0 :1 3 :4 8
5 2 .9 8 %
0 :0 2 :1 3
0 :0 4 :5 1
8 .5 1 %
1 8 .6 2 %
N V A R T o ta l
0 :0 7 :0 4
2 7 .1 3 %
G r a n d T o ta l
0 :2 6 :0 3
1 0 0 .0 0 %
V A T o ta l
NVA
N V A T o ta l
NV AR
M a t. P o s
T .W .S .A .
Ground Crewman #2
Column Data
NVAR
TWSA
19%
VA
19%
NVAR Material
Positioning
9%
NVA Motion
11%
NVA Waiting
32%
NVA
Transport
10%
Figure C.6: Column Data for Ground Crewman 2
197
The crew foreman was involved with positioning and bolting the column into final position.
Table C.3 and Figure C.7 show the VA, NVA and NVAR values for the crew foreman.
According to Table C.3, 25.5 percent of time attributed to the column was VA. The largest
portion of time (52.92 percent) was attributed to NVA actions.
Table C.3: Column Data for the Foreman
VA
T o ta l T im e a t Ac tiv ity
V a lu e A d d in g
0 :0 4 :5 3
2 5 .5 0 %
0 :0 4 :5 3
2 5 .5 0 %
W a itin g
0 :0 8 :4 6
4 5 .7 8 %
E x tra P ro c .
0 :0 1 :2 2
7 .1 4 %
0 :1 0 :0 8
5 2 .9 2 %
0 :0 3 :2 8
0 :0 0 :4 0
1 8 .1 0 %
3 .4 8 %
N V AR T o ta l
0 :0 4 :0 8
2 1 .5 8 %
G ra n d T o ta l
0 :1 9 :0 9
1 0 0 .0 0 %
V A T o ta l
NVA
N V A T o ta l
N V AR
M a t. P o s
T .W .S .A .
Crew Foreman
Column Data
NVAR Material
Positioning
18%
NVAR
TWSA
3%
VA
26%
NVA Extra
Processing
7%
NVA Waiting
46%
Figure C.7: Column Data for the Foreman
The connector was not involved for a significant amount of time; he only assisted in positioning
and bolting the column into its final place. Table C.4 and Figure C.8 show the VA, NVA and
NVAR values for the connector. Contributing only three minutes 10 seconds to the cycle, the
majority of the connector’s time was spent on the NVA action of waiting (86.84 percent). This
left 25 seconds for the VA action of tightening one bolt on the baseplate.
198
Table C.4: Column Data for the Connector
VA
W aste Classification
T otal Time at Activity
Value Adding
VA Total
% of Total T ime
0:00:25
13.16%
0:00:25
13.16%
NVA
0:02:45
86.84%
NVA T otal
M otion
0:02:45
86.84%
G rand Total
0:03:10
100.00%
The Connector
Column Data
VA
13%
NVA Motion
87%
Figure C.8: Column Data for the Connector
The crane operator did not contribute any VA activities to the column erection cycle. Table C.5
and Figure C.9 show the VA, NVA and NVAR values for the crane operator. The crane operator
was primarily involved with transporting columns from their lay-down area to their final position
in the structure. After reaching the baseplate, the crane held the member in a temporary bracing
position until the bolts are sufficiently tightened. These actions contributed to the NVAR
subcategory TWSA value of 59.27 percent.
199
Table C.5: Column Data for the Crane Operator
NVA
Motion
NVA Total
% of Total Time
0:01:00
6.86%
0:01:00
6.86%
0:04:56
33.87%
NVAR
Mat. Pos
0:08:38
59.27%
NVAR Total
T.W.S.A.
0:13:34
93.14%
Grand Total
0:14:34
100.00%
The Crane Operator
Column Data
NVA Motion
7%
NVAR TWSA
59%
NVAR Material
Positioning
34%
Figure C.9: Column Data for the Crane Operator
2.3.2 Pod/Spandrel Beam Erection Cycle
All five members of the crew were observed during the PBC erection cycle. Data for the five
crew members are presented below.
Ground crewman 1 positioned the PBC using tag lines and secured each tag line to anchors (an
adjacent column or bar joist bundle lying on the ground) for temporary support. Table C.6 and
Figure C.10 show the VA, NVA and NVAR values for ground crewman 1. The majority of
ground crewman 1’s time (52.39 percent) was spent waiting. The small amount of VA actions
shown in Table C.6 came from bolting stringer members to the PBC while it was on the ground.
A significant amount of time (19.25 percent) was spent on TWSA functions.
200
Table C.6: PBC Data for Ground Crewman 1
VA
V a lu e A d d in g
0 :0 0 :5 5
0 .6 8 %
0 :0 0 :5 5
0 .6 8 %
W a itin g
1 :1 0 :5 6
5 2 .3 9 %
T ra n s p o rt
M o tio n
0 :1 1 :2 5
0 :1 9 :1 4
8 .4 3 %
1 4 .2 0 %
1 :4 1 :3 5
7 5 .0 2 %
0 :0 6 :0 0
0 :0 0 :5 0
0 :2 6 :0 4
4 .4 3 %
0 .6 2 %
1 9 .2 5 %
N V A R T o ta l
0 :3 2 :5 4
2 4 .3 0 %
G ra n d T o ta l
2 :1 5 :2 4
1 0 0 .0 0 %
V A T o ta l
NVA
N V A T o ta l
NV AR
M a t. P o s
In -P ro c e s s In s .
T .W .S .A .
Ground Crewman #1
PBC Data
NVAR
TWSA
19%
NVAR In-Process
Inspection
1%
NVAR Material
Positioning
4%
NVA Motion
14%
NVA
Transport
8%
VA
1%
NVA Waiting
53%
Figure C.10: PBC Data for Ground Crewman 1
Ground crewman 2 mirrored ground crewman 1 during the PBC erection cycle. He positioned
the PBC with tag lines and secured the tag lines to anchors (an adjacent column or bar joist
bundles). Table C.7 and Figure C.11 show the VA, NVA and NVAR values for ground
crewman 2. Again, a small percentage of VA time was spent bolting stringers to the PBC. The
largest percentage of ground crewman 2’s time was spent on waiting (48.30 percent). The TWSA
category made up 25.29 percent of ground crewman 2’s time.
201
Table C.7: PBC Data for Ground Crewman 2
VA
T o ta l T im e a t Ac tiv ity
V a lu e A d d in g
0 :0 3 :1 4
2 .8 3 %
0 :0 3 :1 4
2 .8 3 %
W a itin g
0 :5 5 :1 7
4 8 .3 0 %
T ra n s p o rt
0 :0 5 :5 3
5 .1 4 %
M o tio n
0 :1 2 :2 6
1 0 .8 6 %
1 :1 3 :3 6
6 4 .3 1 %
0 :0 7 :1 0
0 :0 1 :3 0
0 :2 8 :5 7
6 .2 6 %
1 .3 1 %
2 5 .2 9 %
N V AR T o ta l
0 :3 7 :3 7
3 2 .8 7 %
G ra n d T o ta l
1 :5 4 :2 7
1 0 0 .0 0 %
V A T o ta l
NVA
N V A T o ta l
N V AR
M a t. P o s
T .W .S .A .
Ground Crewman #2
PBC Data
VA
3%
NVAR
TWSA
25%
NVAR In-Process
Inspection
1%
NVAR Material
Positioning
6%
NVA Motion
11%
NVA Waiting
49%
NVA
Transport
5%
Figure C.11: PBC Data for Ground Crewman 2
The foreman was responsible for the following actions: checking each member to ensure the
proper erection sequence, attaching beam clamps to each PBC, positioning the PBC while it was
hoisted off the ground and attaching stringer bars to the PBC while it was on the ground.
Table C.8 and Figure C.12 show the VA, NVA and NVAR values for the foreman. NVA actions,
specifically waiting (73.42 percent), consumed nearly the entire time spent by the foreman on the
PBC. The remaining VA and NVAR actions contributed by the foreman made up only
15 percent, or roughly 16 minutes of the total time.
202
Table C.8: PBC Data for the Foreman
VA
V a lu e A d d in g
0 :0 2 :4 2
2 .2 2 %
0 :0 2 :4 2
2 .2 2 %
W a itin g
1 :2 9 :0 6
7 3 .4 2 %
T r a n s p o rt
0 :0 4 :0 5
3 .3 6 %
M o tio n
0 :1 0 :5 3
8 .9 7 %
1 :4 4 :0 4
8 5 .7 6 %
0 :0 7 :0 1
0 :0 3 :5 5
0 :0 3 :3 9
5 .7 8 %
3 .2 3 %
3 .0 1 %
N V A R T o ta l
0 :1 4 :3 5
1 2 .0 2 %
G r a n d T o ta l
2 :0 1 :2 1
1 0 0 .0 0 %
V A T o ta l
NVA
N V A T o ta l
NV AR
M a t. P o s
T .W .S .A .
Crew Foreman
PBC Data
NVAR Material
Positioning
6%
NVAR
TWSA
3%
NVAR In-Process
Inspection
3%
VA
2%
NVA Motion
9%
NVA
Transport
3%
NVA Waiting
74%
Figure C.12: PBC Data for the Foreman
The connector was involved with the following: positioning and bolting the PBC next to the
adjacent PBC, positioning and bolting the PBC on top of the column, moving the sky lift between
locations and releasing the beam clamps from the PBC after boltup was complete. Table C.9 and
Figure C.13 show the VA, NVA and NVAR values for the connector. The largest contribution to
VA actions during Cycle No. 1 is shown. This accounted for nearly 25 percent of the connector’s
time. However, over two thirds of the connector’s time (70 percent) was spent on the NVA
actions of excess movement and waiting.
203
Table C.9: PBC Data for the Connector
VA
V a lu e A d d in g
0 :3 3 :4 7
2 4 .6 0 %
0 :3 3 :4 7
2 4 .6 0 %
W a itin g
0 :4 4 :3 7
3 2 .4 9 %
E x tra P ro c .
T ra n s p o rt
M o tio n
0 :0 1 :3 2
0 :0 2 :5 8
0 :4 7 :0 1
1 .1 2 %
2 .1 6 %
3 4 .2 4 %
1 :3 6 :0 8
7 0 .0 0 %
0 :0 4 :5 2
0 :0 2 :3 3
3 .5 4 %
1 .8 6 %
N V A R T o ta l
0 :0 7 :2 5
5 .4 0 %
G ra n d T o ta l
2 :1 7 :2 0
1 0 0 .0 0 %
V A T o ta l
NVA
N V A T o ta l
NV AR
M a t. P o s
T .W .S .A .
The Connector
PBC Data
NVAR Material
Positioning
4%
NVAR
TWSA
2%
VA
25%
NVA Motion
34%
NVA
Transport
2%
NVA Waiting
32%
NVA Extra
Processing
1%
Figure C.13: PBC Data for the Connector
The crane operator was responsible for lifting and positioning each PBC into its final position, as
well as providing temporary support for the PBC while alignment and bolting took place.
Table C.10 and Figure C.14 show the VA, NVA and NVAR values for the crane operator. The
majority of the crane operator’s time was spent on TWSA (56.66 percent). This high value for
NVAR actions highlights an area that should be focused on to reduce crane operating costs.
Transport actions occurred when the PBC was lifted one foot off the ground, then held for a
period of time before it was lifted the remaining distance up into position.
204
Table C.10: PBC Data for the Crane Operator
Ac tivity C la ssific a tio n
NV A
W a ste C la ssific a tio n
T o ta l T im e a t Ac tivity
W aitin g
0:10:30
8.34%
E xtra P ro c.
0:01:04
0.85%
T ran sp o rt
M o tio n
0:20:36
0:17:24
16.36%
13.82%
0 :4 9 :3 4
3 9 .3 6 %
NV A T o ta l
NV AR
M at. P o s
0:05:01
3.98%
T .W .S .A.
1:11:21
56.66%
NV AR T o ta l
1 :1 6 :2 2
6 0 .6 4 %
G ra n d T o ta l
2 :0 5 :5 6
1 0 0 .0 0 %
Crane Operator
PBC Data
NVA Waiting
8%
NVA Extra
Processing
1%
NVA
Transport
16%
NVAR
TWSA
57%
NVA Motion
14%
NVAR Material
Positioning
4%
Figure C.14: PBC Data for the Crane Operator
2.3.3 Bar Joist Cycle
The bar joist cycle included the following subtasks: attaching x-bracing to the bar joist on the
ground, setting up choker (rigging) for the crane, positioning the bar joist into the hands of the
connectors above, aligning and positioning the bar joist into its final position, bolting each bar
joist to roof beams, bolting x-bracing to adjacent bar joist and releasing the choker (rigging) from
the bar joist. Figure C.15 shows the major tasks required to complete the bar joist installation.
The shaded areas were used to visually indicate that some tasks took longer to complete than
others, and that those tasks could occur simultaneously with other tasks. The shaded regions are
not intended to show actual task durations.
205
Bar Joist Erection
1
2
3
4
5
6
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Column and Pod Beam Combo Erected
X-Bracing Attached on Ground
Rigging Bar Joist for Crane
Bar Joist Erected Into Place
Aligning Bar Joist
Bolting Ends of Bar Joist
Bolting Opposite End of X-Bracing
Figure C.15: Schedule for Bar Joist Erection Cycle
The second crew was involved with the erection of the bar joist members, and seven new crew
members were observed during this cycle. Again, each worker was referred to by the position that
he/she occupied during the bar joist erection sequence. These references are used to maintain
consistency throughout the analysis. Data for the seven crew members is presented below.
(Refer to the end of this case study to review the data sheets)
The left connector was responsible for aligning and positioning each bar joist member and bolting
the end connections. Table C.11 and Figure C.16 show the VA, NVA and NVAR values for the
left connector. The left connector spent 17.6 percent of his time on VA activities. However, the
largest portion of his time was spent waiting (47.66 percent). This highlights an area that should
be focused on when trying to balance a crew for different activities.
Table C.11: Bar Joist Data for the Left Connector
VA
W a ste C la ssific a tion
V alu e Ad d in g
T ota l T im e a t Ac tivity
0:14:26
17.60%
0 :1 4 :2 6
1 7 .6 0 %
W aitin g
0:39:05
47.66%
E xtra P ro c.
T ran sp o rt
M o tio n
0:03:25
0:01:05
0:07:51
4.17%
1.32%
9.57%
0 :5 1 :2 6
6 2 .7 2 %
V A T o ta l
NV A
NV A T o ta l
NV AR
0:16:08
19.67%
NV AR T o ta l
M at. P o s
0 :1 6 :0 8
1 9 .6 7 %
G ra n d T o ta l
1 :2 2 :0 0
1 0 0 .0 0 %
206
Left Connector
Bar Joist Data
NVAR Material
Positioning
20%
VA
18%
NVA Motion
10%
NVA
Transport
1%
NVA Waiting
47%
NVA Extra
Processing
4%
Figure C.16: Bar Joist Data for the Left Connector
The right connector’s actions mirrored those of the left connector. He was involved with aligning
and positioning each bar joist and bolting the end connection to the roof beam. Table C.12 and
Figure C.17 show the VA, NVA and NVAR values for the right connector. Notice the
similarities in the percentage breakdown of time between the right connector and the left
connector. A similar amount of time was spent on VA actions (18.5 percent). Note that roughly
50 percent of the right connector’s time was wasted on waiting between bar joist cycles.
Table C.12: Bar Joist Data for the Right Connector
VA
V a lu e A d d in g
0:1 5 :10
1 8.5 0%
0 :1 5 :1 0
1 8 .5 0 %
W a itin g
0:4 4 :36
5 4.3 9%
E x tra P ro c.
0:0 0 :46
0.9 3%
M o tio n
0:1 2 :31
1 5.2 6%
0 :5 7 :5 3
7 0 .5 9 %
V A T o ta l
NV A
N V A T o ta l
N V AR
0:0 8 :57
1 0.9 1%
N V AR T o ta l
M at. P o s
0 :0 8 :5 7
1 0 .9 1 %
G ra n d T o ta l
1 :2 2 :0 0
1 0 0 .0 0 %
207
Right Connector
Bar Joist Data
NVAR Material
Positioning
11%
VA
18%
NVA Motion
15%
NVA Extra
Processing
1%
NVA Waiting
55%
Figure C.17: Bar Joist Data for the Right Connector
X-bracing connector 1 was responsible for moving and positioning the sky lift under each bar
joist, hand tightening the bolts and “finish” tightening each bolt with a torque gun. Table C.13
and Figure C.18 show the VA, NVA and NVAR values for x-bracing connector 1. For Crew
No. 2, x-bracing connector 1 performed the largest percentage of VA actions; nevertheless, his
NVA activities still consumed the majority of his time. This sizable NVA amount resulted from
moving the sky lift between each bar joist. The NVA subcategory motion accounted for more
than 41 percent of x-bracing connector 1’s time.
Table C.13: Bar Joist Data for X-Bracing Connector 1
VA
V a lu e A d d in g
V A T o ta l
0 :2 5 :4 5
3 1 .4 0 %
0 :2 5 :4 5
3 1 .4 0 %
NVA
W a itin g
0 :2 0 :5 6
2 5 .5 3 %
M o tio n
0 :3 4 :2 6
4 1 .9 9 %
0 :5 5 :2 2
6 7 .5 2 %
N V A T o ta l
NV AR
0 :0 0 :5 3
1 .0 8 %
N V A R T o ta l
T .W .S .A .
0 :0 0 :5 3
1 .0 8 %
G ra n d T o ta l
1 :2 2 :0 0
1 0 0 .0 0 %
208
X-Bracing Connector #1
Bar Joist Data
NVAR
TWSA
1%
VA
31%
NVA Motion
42%
NVA Waiting
26%
Figure C.18: Bar Joist Data for X-Bracing Connector 1
X-bracing connector 2 was responsible for aligning each x-bracing member into its final position,
assisting in boltup activities and releasing the choker line following boltup. Table C.14 and
Figure C.19 show the VA, NVA and NVAR values for x-bracing connector 2. For the majority
of the bar joist cycle, x-bracing connector 2 was waiting. When the bar joist was in motion,
x-bracing connector 2 focused his time aligning the x-bracing member (32.42 percent) while
x-bracing connector 1 bolted the member into its final position. X-bracing connector 2
contributed time to VA actions when he assisted in bolting the x-bracing member to the adjacent
bar joist.
Table C.14: Bar Joist Data for X-Bracing Connector 2
Activity C lassifica tio n
VA
W a ste C lassific ation
V alu e Ad d in g
V A T o tal
T ota l T im e a t Ac tivity
% o f T o tal T im e
0:05:40
6.91%
0 :05 :4 0
6 .91 %
NV A
W aitin g
0:45:28
55.45%
0 :45 :2 8
55 .4 5%
0:26:35
0:04:17
32.42%
5.22%
NV AR T o ta l
0 :30 :5 2
37 .6 4%
G ra n d T o tal
1 :22 :0 0
1 0 0.0 0 %
NV A T o ta l
NV AR
M at. P o s
T .W .S .A.
209
X-Bracing Connector #2
Bar Joist Data
VA
7%
NVAR
TWSA
5%
NVAR Material
Positioning
32%
NVA Waiting
56%
Figure C.19: Bar Joist Data for X-Bracing Connector 2
Ground crewman 3 was involved with the following: bolting one side of the x-bracing member to
the bar joist while it was on the ground, rigging the bar joist with a choker line and
removing/reattaching the choker line for each bar joist lifted into position. Table C.15 and
Figure C.20 show the VA, NVA and NVAR values for ground crewman 3. Attaching the
x-bracing members to the bar joist while it remained on the ground contributed to the
14.37 percent VA value. Again, the largest percentage of time was wasted on waiting
(60.61 percent).
Table C.15: Bar Joist Data for Ground Crewman 3
VA
V alu e Ad d in g
0:11:47
14.37%
0 :1 1 :4 7
1 4 .3 7 %
W aitin g
0:49:42
60.61%
T ran sp o rt
M o tio n
0:03:40
0:04:42
4.47%
5.73%
0 :5 8 :0 4
7 0 .8 1 %
V A T o ta l
NV A
N V A T o ta l
N V AR
0:12:09
14.82%
N V AR T o ta l
T .W .S .A .
0 :1 2 :0 9
1 4 .8 2 %
G ra n d T o ta l
1 :2 2 :0 0
1 0 0 .0 0 %
210
Ground Crewman #3
Bar Joist Data
NVAR
TWSA
15%
VA
14%
NVA Motion
6%
NVA
Transport
4%
NVA Waiting
61%
Figure C.20: Bar Joist Data for Ground Crewman 3
Ground crewman 4 was solely responsible for positioning each bar joist member into the hands of
the right connector above as the crane was hoisted. Table C.16 and Figure C.21 show the VA,
NVA and NVAR values for ground crewman 4. No VA time was contributed to the cycle by
ground crewman 4. For nearly the entire bar joist cycle, ground crewman 4 was waiting
(81.44 percent). While his presence was needed for those few seconds in a cycle when the bar
joist was being lifted, eliminating this crewman from the group may be a way to increase
productivity.
Table C.16: Bar Joist Data for Ground Crewman 4
NV A
W aitin g
1:06:47
81.44%
T ran sp o rt
0:01:35
1.93%
M o tio n
0:00:30
0.61%
1 :0 8 :5 2
8 3 .9 8 %
NV A T o ta l
NV AR
0:13:08
16.02%
NV AR T o ta l
M at. P o s
0 :1 3 :0 8
1 6 .0 2 %
G ra n d T o ta l
1 :2 2 :0 0
1 0 0 .0 0 %
211
Ground Crewman #4
Bar Joist Data
NVAR Material
Positioning
16%
NVA Motion
1%
NVA
Transport
2%
NVA Waiting
81%
Figure C.21: Bar Joist Data for Ground Crewman 4
Crane operator 2 was responsible for lifting and positioning each bar joist into its final position,
as well as providing temporary support for the bar joist while alignment and bolting took place.
Table C.17 and Figure C.22 show the VA, NVA and NVAR values for crane operator 2. The
percentage of TWSA time (30.71 percent) was slightly higher than the percentage of time spent
waiting (30.41 percent). Waiting occurred each time the crane sat while ground crewman 3
hooked up the choker line to the crane ball. It also occurred after the crane lifted the bar joist one
foot off the ground and held it there until the connectors above were ready to receive the next bar
joist.
Table C.17: Bar Joist Data for Crane Operator 2
NVA
W a itin g
0 :2 4 :5 6
T ra n s p o rt
0 :0 5 :3 0
6 .7 1 %
M o tio n
0 :1 2 :5 0
1 5 .6 5 %
0 :4 3 :1 6
5 2 .7 6 %
0 :1 3 :3 3
0 :2 5 :1 1
1 6 .5 2 %
3 0 .7 1 %
N V A R T o ta l
0 :3 8 :4 4
4 7 .2 4 %
G ra n d T o ta l
1 :2 2 :0 0
1 0 0 .0 0 %
N V A T o ta l
3 0 .4 1 %
NV AR
M a t. P o s
T .W .S .A .
212
Crane Operator #2
Bar Joist Data
NVAR
TWSA
30%
NVA Waiting
30%
NVA
Transport
7%
NVAR Material
Positioning
17%
NVA Motion
16%
Figure C.22: Bar Joist Data for Crane Operator 2
As previously mentioned, two different crews were observed. The crew balance chart for Crew
No. 1 is shown on Figure C.23. The crew balance chart for Crew No. 2 is shown on Figure C.24.
These charts were compiled using the average times generated from the entire set of data
observations. These average times were used to create an “idealized” crew balance.
3.1 Crew Composition 1: Column and PBC Erection
(Cycle No. 1)
This crew balance chart includes the five crew members observed during the column and PBC
erection cycle. The different sections represent the major tasks for each worker. The driver for
Cycle No. 1 was the connector. While the connector was not significantly involved in the column
cycle, his time attributed to the PBC caused the remaining members of the crew to wait while he
completed all of his tasks to free up the crane for the next column. The average computed time
from each task was used to create a cycle’s duration. Once an iteration of the cycle started, the
times for each activity were observed to maintain similar results during each new cycle.
However, variations in total cycle time occurred due to Crew No. 2’s inability to keep up with
Crew No. 1. The average cycle time for Crew No. 1 was 20 minutes 30 seconds. This time did
not include the total time required to reposition the crane, sky lift and crew at the new position.
The high percentage of waiting within Cycle No. 1 highlights an area where waste could be
reduced.
It is important to note that Figure C.23 represents an idealized crew balance using average task
times. This ideal cycle is typically shorter than the actual cycle time in which task time
variability causes an increase in the overall cycle time.
213
TIME
0:20:30
0:20:15
0:20:00
0:19:45
0:19:30
0:19:15
0:19:00
0:18:45
0:18:30
0:18:15
0:18:00
0:17:45
0:17:30
0:17:15
0:17:00
0:16:45
0:16:30
0:16:15
0:16:00
0:15:45
0:15:30
0:15:15
0:15:00
0:14:45
0:14:30
0:14:15
0:14:00
0:13:45
0:13:30
0:13:15
0:13:00
0:12:45
0:12:30
0:12:15
0:12:00
0:11:45
0:11:30
0:11:15
0:11:00
0:10:45
0:10:30
0:10:15
0:10:00
0:09:45
0:09:30
0:09:15
0:09:00
0:08:45
0:08:30
0:08:15
0:08:00
0:07:45
0:07:30
0:07:15
0:07:00
0:06:45
0:06:30
0:06:15
0:06:00
0:05:45
0:05:30
0:05:15
0:05:00
0:04:45
0:04:30
0:04:15
0:04:00
0:03:45
0:03:30
0:03:15
0:03:00
0:02:45
0:02:30
0:02:15
0:02:00
0:01:45
0:01:30
0:01:15
0:01:00
0:00:45
0:00:30
0:00:15
0:00:00
Crew Balance Chart Cycle No.1
Waiting
Waiting
Waiting
Waiting
Waiting
Waiting
Booming down
to move to next
position
Waiting
Booming Down
Moving to
next position
Releasing Beam
Clamps from
P.B.C.
Waiting
Waiting
Waiting
Waiting
Waiting
Waiting
Moving
Waiting
Waiting
Waiting
Waiting
Waiting
Waiting
Waiting
Waiting
Waiting
Bolting First
Side of P.B.C.
again
Holding PBC
In Position
while Bolt-Up
occurs
Moving Sky Lift
Waiting
Bolting opp.
Side of P.B.C. to
top of Column
Moving Sky Lift
Securing Tag Line
to adjacent Column
Securing Tag Line
to adjacent Column
Waiting
Holding PBC
In Position
while Bolt-Up
occurs
Bolting P.B.C. to
top of Column
Waiting
walking
walking
Moving to top
of Column in
Sky Lift
Securing Tag Line
to material on
ground
Securing Tag Line
to material on
ground
Bolting Opp.
Side of connection
Waiting
Moving Sky Lift
Walking
Using tag lines
to Position
P.B.C. while it
is lifted into position
Walking
Using tag lines
to Position
P.B.C. while it
is lifted into position
Bolt two P.B.C.
Together
Waiitng
Positioning PBC
next to adjacent PBC
Moving Sky Lift
Waiting
Removing Tag
Line from previous
P.B.C
Releasing Crane
Rigging
Removing Tag
Line from previous
P.B.C
Waiting
Holding Pod
Beam Combo
Inspecting Plans
Waiting
Releasing Crane
Rigging
Waiting
Bolting Stringers
onto P.B.C.
Bolting Column
to Base Plate
Bolting Column
to Base Plate
Positioning Col
Onto =Base Plate
Positioning Col
onto Base Plate
Ground Crewman 1
Lifting
Waiitng
Waiting
Waiting
Holding PBC
In Position
while Bolt-Up
occurs
Moving Sky Lift
to Next Position
Holding P.B.C.
while on ground
Attaching Rigging
to Crane ball
Securing Beam
Clamps around
P.B.C.
Bolting Column
to Base Plate
Holding Column
In Position
While Bolting occurs
Positioning Col
onto Base Plate
Lifting Column
into position
Attaching Rigging to
Crane - COL.
Rigging Column
With Crane hoist Line
Ground Crewman 2
Connector
Foreman
Figure C.23: Crew Balance Chart - Cycle No. 1
214
Lowering Hoist Line
to be removed
Moving and
Setting up For
Next Lift
Crane Op.
The average time that it took the crane to lift the column into position was one minute
14 seconds, and it took four minutes 53 seconds to lift the PBC from the ground into position.
The PBC time included lifting the member one foot off the ground, holding it in that position
until the connectors were ready, and finally lifting the PBC the remaining distance into position.
The crew balance chart shows that the majority of time for both ground crewmen was spent
waiting. The average waiting time during each cycle for ground crewman 1 was two minutes
46 seconds, and the average waiting time for ground crewman 2 was three minutes 13 seconds.1
Waiting accounted for 41 percent of the total time contributed by the group to the column and
PBC cycle (refer to Table C.20 summary sheet for Cycle No. 1). For each cycle, each crewman
contributed roughly seven minutes to the NVA category of waste. This value sums up the
multiple independent waiting periods that occurred between activities for each ground crewman.
It is shown as one lump segment to simplify the balance chart for easier reading.
3.2 Crew Composition 2: Bar Joist Erection (Cycle No. 2)
Figure C.24 shows the crew balance chart for the bar joist erection cycles. The cycle times for
the bar joist erection were significantly shorter than the cycle times observed for the column and
PBC erection. Even though less time was required for the erection of each bar joist, Crew No. 2
had to erect 12 bar joists per bay before the crane could be moved to the next position. Cycle
No. 2 was assumed to have fewer waiting periods because there was only one type of structural
member the crew erected (as compared to Crew No. 1 with the column and PBC members).
However, each member in Crew No. 2 spent large amounts of time waiting.
Each bar joist member took roughly two minutes 45 seconds to erect. It took Crew No. 2
approximately 33 minutes to erect the 12 bar joists per bay. The driver for this activity was the
crane operator, who contributed a large portion of the cycle time to holding the bar joist in
position while boltup occurred. This action contributed to the NVAR time for the cycle. While
this action may never be completely eliminated from the erection cycle, it could be minimized by
focusing on each crew member’s task while the crane holds the bar joist in position. Refer to
Table C.18 for the waste percentage breakdown for Cycle No. 2.
On average, it took 51 seconds for the crane to hold the bar joist in final position to allow boltup
to occur. The minimum time for this activity was 19 seconds, while the maximum time was two
minutes 55 seconds. This variability in task time highlights an area where cycle time could be
reduced. If Crew No. 2 could consistently position and bolt each bar joist member in 19 seconds,
41 seconds could be eliminated from the bar joist cycle time. This in turn could shave more than
6 minutes from the “ideal” cycle represented on Figure C.24. A large portion of time for the
remaining crewmen was wasted on waiting; roughly 51 percent of the total crew time during
Cycle No. 2 was wasted on waiting. This amounted to four hours 51 minutes 30 seconds of
waiting time shared between the members of Crew No. 2. Refer to Table C.21 for the bar joist
cycle waste percentage breakdown.
1
Note that the discrepancy between the two ground crewmen may be due to observer error. The crew
balance chart is an idealized representation for a column and PBC erection crew. This ideal crew balance is
structured around the crane operator’s movements.
215
TIME
0:10:00 Hand Tightening Bolts
0:09:45
0:09:30 Moving Sky Lift
0:09:15
Waiting
0:09:00
0:08:45
Waiting
0:08:30
0:08:15
0:08:00
0:07:45 Tightening bolts
0:07:30 with an impact gun
0:07:15 Hand Tightening
Bolts
0:07:00
0:06:45
0:06:15
Waiting
0:06:00
0:05:45
Waiting
0:05:30
0:05:15
0:05:00
Bolts
0:04:00
0:03:45
0:03:15
Waiting
0:03:00
0:02:45
Waiting
0:02:30
0:02:15
0:02:00
Bolts
0:01:00
0:00:45
0:00:15
Waiting
0:00:00
X-BConnector #1
CrewBalance Chart Cycle #2
Pos. Bar Joist
Pos. Bar Joist
Positioning XB
Waiting
Waiting
Waiting
Waiting
Waiting
Waiting
Moving
Moving
Bolting Bar Joist
Bolting Bar Joist
to Girder
Waiting
Releasing Crane Rig
Positioning
Bar Joist
Positioning XB
Lifting B.J. into Pos.
Waiting
Waiting
Waiting
Waiting
Moving
Moving
Bolting Bar Joist
Bolting Bar Joist
to Girder
Waiting
Releasing Crane Rig
Positioning
Bar Joist
Waiting
Waiting
Waiting
Waiting
Moving
Moving
Bolting Bar Joist
Bolting Bar Joist
to Girder
Waiting
Positioning
Bar Joist
Waiting
Left Connector
Waiting
Waiting
Right Connector
Lifting 1ft off ground
Waiting For
Hookup
Lowering Hoist Line
Waiting
Holding Bar Joist
While Bolt up occurs
Waiting
Waiting
Positioning
Bolting one side
of X-B to Bar Joist
Ground Crewman #3
Waiting
Waiting
Waiting
X-BConnector #2
Waiting
Waiting
Positioning XB
Waiting
Positioning
Waiting
Waiting
Releasing Crane Rig
Holding Bar Joist
Waiting
Bolting one side
of X-B to Bar Joist
Hooking up Hoist line
Prepping Bar Joist
Positioning
Bar Joist
Waiting
Waiting For
Hookup
Lowering Hoist Line
Waiting
Waiting
Positioning XB
Waiting
Waiting
Positioning XB
Waiting
Positioning
Waiting
Waiting
Positioning
Bar Joist
Holding Bar Joist
Waiting
Bolting one side
of X-B to Bar Joist
Prepping Bar Joist
Positioning XB
Waiting
Waiting For
Hookup
Lowering Hoist Line
Waiting
Waiting
Waiting
Waiting
Waiting
Positioning
Bar Joist
Waiting
Waiting
Bolting one side
of X-B to Bar Joist
Prepping Bar Joist
Positioning XB
Waiting
Positioning
Waiting
Ground Crewman #4
Crane Operator #2
Figure C.24: Crew Balance Chart - Cycle No. 2
3.3 General Observations About Crew Composition
During both observed cycles, the majority of time was spent waiting. In Crew No. 1, the foreman
waited for nearly the entire cycle time. His contributions to the NVAR action of in-process
inspections involved checking the plans to ensure a correct erection sequence. This action of
checking the steel members appears to be redundant because the columns and roof beam
components were already placed on the ground in the order of erection. The remaining actions
contributed by the foreman in Cycle No. 1 could have easily been handled by crew members 1
and 2, thus eliminating the foreman from the cycle. In Crew No. 2, ground crewman 4 was
expendable since his only contribution was positioning each bar joist into the hands of the
connectors above as it was lifted by the crane. This task could have easily been handled by
ground crewman 3, reducing his waiting time, as well as the entire waiting percentage for the
entire crew on the bar joist cycle. The results in Tables C.18 through C.21 show the variations of
VA, NVA and NVAR for each cycle. These variations highlight the difficulty of correctly sizing
a crew for multiple activities on a construction site.
216
Table C.18: Waste Percentage Breakdown with Both Crews
Steel Erection - Cycle #1
Crew Member
VA
All
Activities
Crew for Cycle 1
Ground Crewman #1
Ground Crewman #2
Connector
Foreman
Crane Operator #1
Crew For Cycle 2
Left Connector
Right Connector
X-Bracing Con. #1
X-Bracing Con. #2
Ground Crewman #3
Ground Crewman #4
Crane Operator #2
Group Percentage
Waste
VA +
NVAR
%
19%
24%
2%
3%
57%
100%
100%
100%
100%
100%
26%
38%
30%
19%
64%
0%
0%
0%
0%
0%
0%
0%
0%
0%
1%
5%
15%
0%
31%
100%
100%
100%
100%
100%
100%
100%
37%
29%
32%
45%
29%
16%
47%
0%
15%
100%
35%
14%
11%
35%
8%
13%
5%
7%
3%
7%
7%
1%
1%
0%
3%
0%
1%
0%
0%
0%
4%
2%
7%
10%
15%
42%
0%
6%
1%
16%
20%
11%
0%
32%
0%
16%
17%
5%
15%
9%
Waiting
Extra
Processing
1%
6%
24%
5%
0%
52%
45%
32%
70%
7%
0%
0%
1%
1%
1%
8%
6%
2%
3%
15%
18%
19%
31%
7%
14%
0%
0%
48%
54%
26%
55%
61%
81%
30%
4%
1%
0%
0%
0%
0%
0%
10%
46%
1%
Transport Movement
21:16:30 AM h:m:s
Total %
Material
Pos.
NVAR
In Proc.
Ins.
T.W.S.A
Table C.19: Summary of Cycle No. 1 - Column and PBC
Columns
Crew Member
Ground Crewman #1
Ground Crewman #2
Connector
Foreman
Crane Operator #1
VA
All
Activities
16%
20%
13%
26%
0%
Group Percentage
Pod Beam Combo
Crew Member
Ground Crewman #1
Ground Crewman #2
Connector
Foreman
Crane Operator #1
17%
Waste
39%
33%
0%
46%
0%
Extra
Processing
0%
0%
0%
7%
0%
28%
2%
Waiting
0%
10%
0%
0%
0%
0%
11%
87%
0%
7%
Material
Pos.
29%
9%
0%
18%
34%
4%
10%
18%
Transport Movement
NVAR
In Proc.
Ins.
0%
0%
0%
0%
0%
0%
Total Cumulative Time Spent on PBC
VA
All
Activities
1%
3%
25%
2%
0%
Group Percentage
6%
Waiting
52%
48%
32%
73%
8%
43%
Waste
Extra
Transport Movement
Processing
0%
8%
14%
0%
5%
11%
1%
2%
34%
0%
3%
9%
1%
16%
14%
0%
7%
17%
Material
Pos.
4%
6%
4%
6%
4%
NVAR
In Proc.
Ins.
1%
1%
0%
3%
0%
5%
1%
1:08:02 h:m:s
T.W.S.A
16%
19%
0%
3%
59%
Total %
100%
100%
100%
100%
100%
100%
22%
10:34:28 h:m:s
VA +
NVAR
%
61%
47%
13%
47%
93%
56%
19%
25%
2%
3%
57%
100%
100%
100%
100%
100%
VA +
NVAR
%
25%
36%
30%
14%
61%
21%
100%
33%
T.W.S.A
Total %
Table C.20: Summary of Subtasks for Cycle No. 1
Steel Erection - Cycle #1
Crew Member
Ground Crewman #1
Ground Crewman #2
Connector
Foreman
Crane Operator #1
Group Percentage
VA
Waste
All
Extra
Material
Waiting
Transport Movement
Activities
Processing
Pos.
1%
52%
0%
8%
14%
5%
6%
45%
0%
6%
11%
7%
24%
32%
1%
2%
35%
3%
5%
70%
1%
3%
8%
7%
0%
7%
1%
15%
13%
7%
7%
41%
1%
7%
217
16%
6%
NVAR
In Proc.
Ins.
1%
1%
0%
3%
0%
1%
11:42:30 h:m:s
19%
24%
2%
3%
57%
100%
100%
100%
100%
100%
VA +
NVAR
%
26%
38%
30%
19%
64%
21%
100%
35%
T.W.S.A
Total %
Table C.21: Summary for Cycle No. 2 Bar Joists
Bar Joists
Crew Member
Left Connector
Right Connector
X-Bracing Con. #1
X-Bracing Con. #2
Ground Crewman #3
Ground Crewman #4
Crane Operator #2
Group Percentage
VA
All
Activities
18%
19%
31%
7%
14%
0%
0%
13%
Waste
48%
54%
26%
55%
61%
81%
30%
Extra
Processing
4%
1%
0%
0%
0%
0%
0%
51%
1%
Waiting
1%
0%
0%
0%
4%
2%
7%
10%
15%
42%
0%
6%
1%
16%
Material
Pos.
20%
11%
0%
32%
0%
16%
17%
2%
13%
14%
Transport Movement
NVAR
In Proc.
Ins.
0%
0%
0%
0%
0%
0%
0%
0%
9:34:00 h:m:s
0%
0%
1%
5%
15%
0%
31%
100%
100%
100%
100%
100%
100%
100%
VA +
NVAR
%
37%
29%
32%
45%
29%
16%
47%
7%
100%
34%
T.W.S.A
Total %
applying Ohno’s (Shingo and Dillon 1989) seven wastes in production and then evaluating the
Table C.18 shows the time spent on VA, NVA and NVAR activities as a percentage of total
cumulative time spent by both crews during the observation period of the steel erection process.
Table C.19 shows the subset of activities that occurred to accomplish the column and PBC
erection process. Tables C.20 and C.21 show the total percentage breakdown for the observed
cycles. The NVA category is further divided into time spent in the waiting, extra processing,
transport and movement categories. Additionally, NVAR is broken down into its three
subcategories to clarify how time was spent within the observed cycles.
4.1.1 Waiting
Waiting accounts for nearly half of the total time observed for each cycle shown above in
Tables C.18 through C.21. The column erection cycle shows the least amount of waiting at
28 percent, followed by the PBC cycle at 43 percent. Waiting for both crews was highly
dependent on the structure of the crew and the task that the crew was focused on during the
observation period. For example, the column erection cycle required both ground crewmen to
help align and position the column on the baseplate, while the erection of a bar joist might have
only require one ground crewman to position it into the hands of the connectors above.
For both crews, wasted motion occurred each time the sky lift was moved between column lines,
roof beam connection points and bar joist members that were erected during each cycle. Wasted
motion also occurred each time the ground crewmen walked between anchor points to secure the
column and PBC during Cycle No. 2. Finally, motion was wasted each time the connectors
moved between connection points for each bar joist member. The percentage of total time wasted
due to motion for the column, PBC and bar joist cycles was 10, 17, and 13 percent, respectively.
218
required modification. This included any preparation work around connection points such as
cleaning out any metal slag that remained in the bolt holes from the manufacturer and any
preparation work required for the bolts prior to insertion into the bolt holes. During the PBC and
bar joist erection, connection points were hammered to make the connections fit together. While
this type of waste did not consume a large portion of time during either cycle (one percent), it
could still be easily eliminated.
Minimal amounts of transportation waste (five percent) occurred during either cycle. The largest
percentage of transportation waste (seven percent) occurred during the PBC erection cycle when
one of the PBC members was lifted and positioned in a different location so that the column for
that bay could be erected. Material layout on the jobsite minimized this type of waste. Material
transport occurred when each structural element was maneuvered via hauling trucks to their
temporary positions along the column lines. Due to the limitations of the study, this action was
not observed by the team and is not accounted for in this case study. Other observations of
material transportation occurred with the ground crew as they carried rigging from one column
line to the next.
4.2.1 Overproduction/(WIP)
produced. Work in Progress (WIP), on the other hand, is evident in construction but is dependent
on the activity level being viewed. At the process-specific level, WIP is seldom observed.
However, at the management level, each unfinished component of the production process
represents WIP. For this study, WIP was represented by the unfinished structure.
4.2.2 Inventory
Material deliveries were made continually throughout the construction process. The steel was
delivered onsite on large flatbed trucks. Typically four rows of steel, each row consisting of
10 bays, were delivered in one shipment to the jobsite. The material remained onsite anywhere
from one day to a week and a half before being erected into place. The systematic process of
erecting a column, PBC, then bar joists within each bay continued through the first four rows; the
foundation walls were unfinished along the north side of the structure. While the cycles viewed
were not affected by the incomplete foundation, future cycles will be. The outcome will be a
sporadic erection sequence in which the structural members remain as inventory until the
foundation wall is finished.
4.2.3 Defects
Defects are defined as errors or deficiencies in a finished product that required additional work on
219
to the next work station). Another example of a defect is included in the punch list process at the
crew is activated to correct the defect. Hence, the defect is pushed onto the next work station.
No waste associated with defects was observed.
process, beginning with the time the material was ordered and shipped from the manufacturer,
facility. Figure C.25 is a simple flow diagram, with each box representing a point in time when
the material was touched either to be moved or transformed into its next stage (phase) in the
Manufacturer
Initial
Dropoff
Pod Beam Connected
to Spandrel Beam,
Positioned with Column
Next to Bay
Initial Shakeout. All
Structural Elements for
One Bay Are Pulled
from Pile
Bar Joists are
Organized in Order of
Erection and
Positioned Parallel to
Column Lines
Final Placement
by Crane
Bar Joist Bundles
Are Picked Up and
Positioned under
Crane
Figure C.25: Material Flow Diagram
Information on delivery and handling of the steel members was obtained from the project
superintendent. Once it arrived onsite, the basic flow of the steel was as follows.
The steel subcontractor was responsible for ordering and ensuring on-time delivery of all steel
used on the project. The bar joists used on the project were provided by the subcontractor’s own
steel manufacturing plant. The tube columns, spandrel beams and pod beams were all produced
by various steel manufacturers throughout the United States. This required an onsite steel
erector’s management team to coordinate the deliveries from each mill. The responsibility for
handing material (steel) movement once it was delivered onsite was transferred to the project’s
general contractor.
The delivery of the erected steel was not observed. The basic movement of the steel was as
follows. The steel was ordered in three phases for the structure; each phase contained all the steel
necessary to erect four rows and the interconnecting bays. The steel members were delivered in
bundles of like elements. From the truck, the bundles were positioned on the ground next to the
truck. The truck then left the site, allowing for the next truck to enter the lay-down area. One
forklift was dedicated to moving the material from the truck onto the ground, and a second
forklift was used to shake out the material and position it so that it lay parallel to the column
lines. Each structural element required in a bay was positioned on the ground in the adjacent bay
until the erecting crew was ready. Finally, a third forklift repositioned the bar joist bundles so
that they were in the correct order of the erection sequence. After the material was positioned on
the ground, the erection crews moved in to start the erection cycles. There were minimal
incidences of double handling occurred by either crew once the erection process was started.
220
5.1 Case Study No. 3’s Value Stream Map
For the following value stream map analysis, three levels were required to represent both the
material and labor components. Level One represents the major “Staging Positions” material
went through to reach its finished state. Each time material was moved or transformed, a stage
box is used to represent the process. Some of the stages include substages (Level Two) that
represent processes that occurred simultaneously. The individual crew contributions to the value
stream are represented on Level Three.
The value stream map on Figure C.26 was created using available information; Figures C.27
C.28, and C.29 show magnified views for each level. For this case study, the value stream
represents material and worker movements associated with both crews. The weighted average
values for each work distribution category represent input from both crews. These values are
assumed to be a reasonable representation for the entire steel erection processes on the project.
Each major stage that the steel members went through is represented on Level One. For Stage
Four, substage boxes are assigned to each crew. Taken together, all tasks necessary for
completion of the structural steel erection process are identified.
The steel was offloaded from the truck, shaken-out and prepped (PBC bolted together on the
ground) before the erection process Stage Four could begin. All shakeout activities were
represented as one stage (Stage Two). Stage Three covered the first VA actions committed by the
crew. The value stream ended once the steel erection process reached the detailing and welding
stage. Again, the limited observation period prevented acquisition of data at this stage in the
entire steel erection process. Attention was instead focused on the two substages required for
Stage Four of the value stream. The majority of time spent in Levels Two and Three was on the
column and PBC erection phase. The amount of time spent on the bar joist erection process was
not far behind. The separation of the required erection tasks between the two crews allowed for a
more balanced production process. Even though the total time spent by each crew on its
respective tasks was relatively equal, the overall work distribution values for waste were still high
(65 percent weighted NVA value). Attention should be placed on the individual tasks required of
each crew member. Once the tasks within each crew become balanced, the overall process will
go faster and the VA percentage will rise. The largest contribution to the NVAR category was
when the crane operator was required to temporarily hold the steel members in position while
boltup occurred.
Table C.22 and Figure C.30 show the Quick Summary results for the work distribution values
from Level One. The value stream map depicts the flow of material and workers for the entire
steel erection process.
Of 1,544 total workable hours committed to the steel erection process by these crews, only 152 of
them were VA. The largest amount of time was spent on NVA actions (1,018 man-hours). A
significant amount of NVAR time came from the crane operators. This number could be reduced
even further if the tasks required of each crew member were evenly distributed. The ground
crewmen in Crew No. 1 also contributed to this number by securing tag lines.
221
Production Control
Every 1-3 days
Project Engineer
Triggering Event
Percent Complete
Order is made for all SS within one of three zones
Project Feedback
Level One
Steel In Place awaiting
welding
Steel Supplier
As Required
Time Allocation Feild
Daily
3 days of shipments for each zone
O
O OO
NVA Time
NVAR Time
1
VA Time
Work Time
0
respective Bays
Days Required
Equipment involved:
Forklifts
Workers involved
Crew
WT
VA ( 0%)
NVAR (20%)
NVA (80%)
2
2
3
48
0
9.6
38.4
Inv
Stage Two - Steel is shookout
Days
2
Required
Equipment involved:
Forklifts
2
Workers involved
Crew
2
WT
32
VA ( 0%)
0
NVAR (0%)
0
NVA (100%)
32
2
Stage Three - Pod Beam are attached
to Spandel Beam
Days Required
5
Equipment involved:
Forklifts
Workers involved
Crew
WT
VA ( 10%)
NVAR (25%)
NVA (65%)
Inv
Stage Four - Steel Erection
Process
Days Required
2
80
8
20
52
Inv
5
Level Three
16.5
Equipment involved:
Forklift, Skylift
Workers involved
Crew
WT=
VA ( 7%) =
NVAR (28%) =
NVA (65%) =
5
Avail time/day
8
Days Required
660
46
185
429
Column and Pod Beam Erection Cycle-Case study #5
Waste
NVAR
VA
Crew Member
All
Extra
Transport Movement Material Pos.
Waiting
In Proc. Ins.
Processin
Activitie
Ground Crewman #1
Ground Crewman #2
Connector
Foreman
Crane Operator #1
1%
6%
24%
5%
0%
Group Percentage
7%
52%
45%
32%
70%
7%
0%
0%
1%
1%
1%
41%
1%
NVA Sum
Bar Joist Data from Case Study #5
VA
Crew Member
All
Waiting
Activitie
Left Connector
18%
48%
Right Connector
19%
54%
X-Bracing Con. #1
31%
26%
X-Bracing Con. #2
7%
55%
Ground Crewman #3
14%
61%
Ground Crewman #4
0%
81%
Crane Operator #2
0%
30%
Group Percentage
13%
51%
Group Percentage
10%
Waiting
7%
14%
11%
35%
8%
13%
5%
7%
3%
7%
7%
16%
6%
65%
Avail time/day
T.W.S.A
1%
1%
0%
3%
0%
19%
24%
2%
3%
57%
1%
21%
NVAR Sum
Waste
Extra
Transport Movement
Processin
4%
1%
10%
1%
0%
15%
0%
0%
42%
0%
0%
0%
0%
4%
6%
0%
2%
1%
0%
7%
16%
2%
1%
T.W.S.A
20%
11%
0%
32%
0%
16%
17%
0%
0%
0%
0%
0%
0%
0%
0%
0%
1%
5%
15%
0%
31%
0%
7%
VA +
NVAR %
100%
100%
100%
100%
100%
26%
38%
30%
19%
64%
100%
35%
Total %
VA +
NVAR %
100%
100%
100%
100%
100%
100%
100%
37%
29%
32%
45%
29%
16%
47%
100%
34%
Total %
VA +
NVAR %
21%
NVAR Sum
Waste
Extra
Transport Movement
Processin
Total %
NVAR
14%
8
28%
In Proc. Ins.
13%
755
98
159
499
9:34:00 h:m:s
Material Pos.
66%
Note: Step 1 and 2 occur at the same time. Step 1 is
required to occur first, but cannot proceed to far in the
erection sequence until step 2 is completed per bay.
11:42:30 h:m:s
Total Cumulative Time Spent on Bat Joists
NVA Sum
Average Values for Case Study
VA
Crew Member
All
Activitie
Crew for Cycle 1
Ground Crewman #1
1%
Ground Crewman #2
6%
Connector
24%
Foreman
5%
Crane Operator #1
0%
Crew For Cycle 2
Left Connector
18%
Right Connector
19%
X-Bracing Con. #1
31%
X-Bracing Con. #2
7%
Ground Crewman #3
14%
Ground Crewman #4
0%
Crane Operator #2
0%
8%
6%
2%
3%
15%
13.5
Equipment involved:
Forklift, Skylift
2
Workers involved
Crew
7
WT=
VA ( 13%) =
NVAR (21%) =
NVA (66%) =
2
NVAR
Material Pos.
In Proc. Ins.
T.W.S.A
52%
45%
32%
70%
7%
0%
0%
1%
1%
1%
8%
6%
2%
3%
15%
14%
11%
35%
8%
13%
5%
7%
3%
7%
7%
1%
1%
0%
3%
0%
19%
24%
2%
3%
57%
100%
100%
100%
100%
100%
26%
38%
30%
19%
64%
48%
54%
26%
55%
61%
81%
30%
4%
1%
0%
0%
0%
0%
0%
1%
0%
0%
0%
4%
2%
7%
10%
15%
42%
0%
6%
1%
16%
20%
11%
0%
32%
0%
16%
17%
0%
0%
0%
0%
0%
0%
0%
0%
0%
1%
5%
15%
0%
31%
100%
100%
100%
100%
100%
100%
100%
37%
29%
32%
45%
29%
16%
47%
15%
9%
0%
15%
100%
35%
46%
Total Cumulative Time - Column and Pod Beam
Total Cumulative Time - Bar Joists
Total Time
1%
5%
Cumulative
Time for
various
11:42:30
9:34:00
21:16:30
Number of
members
observed
4
24
Cycle time
% of Total Time
% of Total Time
for each
each steel
element
element requires
2:55:38
55%
47%
0:23:55
45%
6%
6:14:49 Man-Hours for one Bay
Figure C.26: Value Stream Map
222
2000
Working Days
39
Working Time
1576 man hours
VA Total
152 man hours
NVAR Total
373 man hours
NVA Total
1050 man hours
Step 2: Bar Joist installed
along with x-bracing members
Step 1: Column and Spandel Beam
Days Required
1500
Inventory Days
12
5
Level Two
1000
Manhours
30
Equipment involved:
Forklifts
4
Workers involved
Crew
12
WT=
1416
VA ( 7%, 13%)
144
344
NVAR (28%, 21
928
NVA (65%,66%
1
500
10%
25%
65%
Production Control
Triggering Event
Order is made for all SS within one of three zones
E v e ry 1 -3 d a y s
Project Engineer
Percent Complete
Project Feedback
Level One
Steel In Place awaiting
welding
Steel Supplier
As Required
T im e A llo c a tio n F e ild
Daily
3 days of shipments for each zone
O
O OO
NVA Time
NVAR Time
1
VA Time
Work Time
0
respective Bays
Days Required
Equipment involved:
Forklifts
Workers involved
Crew
WT
VA ( 0%)
NVAR (20%)
NVA (80%)
2
2
3
48
0
9.6
38.4
Inv
2
Stage Two - Steel is shookout
Days
2
Required
Equipment involved:
Forklifts
2
Workers involved
Crew
2
WT
32
VA ( 0%)
0
NVAR (0%)
0
NVA (100%)
32
Stage Three - Pod Beam are attached
to Spandel Beam
Days Required
Inv
Equipment involved:
Forklifts
Workers involved
Crew
WT
VA ( 10%)
NVAR (25%)
NVA (65%)
Stage Four - Steel Erection
Process
5
Days Required
1
2
80
8
20
52
Inv
5
5
500
1000
1500
2000
Manhours
30
Equipment involved:
Forklifts
4
Workers involved
Crew
12
WT=
1416
VA ( 7%, 13%)
144
344
NVAR (28%, 21
NVA (65%,66%
928
Working Days
39
Working Time
1576 man hours
VA Total
152 man hours
NVAR Total
373 man hours
NVA Total
1050 man hours
Inventory Days
12
Figure C.27: Level One
Step 1: Column and Spandel Beam
Level Two
Days Required
16.5
Equipment involved:
Forklift, Skylift
Workers involved
Crew
WT=
VA ( 7%) =
NVAR (28%) =
NVA (65%) =
5
Avail time/day
8
2
660
46
185
429
Figure C.28: Level Two
223
Step 2: Bar Joist installed
along with x-bracing members
Days Required
13.5
Avail time/day
8
Note: Step 1 and 2 occur at the same time. Step 1 is
required to occur first, but cannot proceed to far in the
Equipment involved:
erection sequence until step 2 is completed per bay.
Forklift, Skylift
2
Workers involved
Crew
7
WT=
755
VA ( 13%) =
98
NVAR (21%) =
159
NVA (66%) =
499
Level Three
Column and Pod Beam Erection Cycle-Case study #5
Waste
NVAR
VA
Crew Member
All
Extra
Waiting
Transport Movement Material Pos. In Proc. Ins.
Activitie
Processin
Ground Crewman #1
1%
52%
0%
8%
14%
5%
1%
Ground Crewman #2
6%
45%
0%
6%
11%
7%
1%
24%
32%
1%
2%
35%
3%
0%
Connector
Foreman
5%
70%
1%
3%
8%
7%
3%
Crane Operator #1
0%
7%
1%
15%
13%
7%
0%
Group Percentage
7%
41%
NVA Sum
Bar Joist Data from Case Study #5
VA
Crew Member
All
Waiting
Activitie
18%
48%
Left Connector
19%
54%
Right Connector
X-Bracing Con. #1
31%
26%
X-Bracing Con. #2
7%
55%
Ground Crewman #3
14%
61%
Ground Crewman #4
0%
81%
Crane Operator #2
0%
30%
Group Percentage
13%
51%
NVA Sum
Average Values for Case Study
VA
Crew Member
All
Waiting
Activitie
Crew for Cycle 1
Ground Crewman #1
1%
52%
Ground Crewman #2
6%
45%
24%
32%
Connector
Foreman
5%
70%
Crane Operator #1
0%
7%
Crew For Cycle 2
Left Connector
18%
48%
Right Connector
19%
54%
X-Bracing Con. #1
31%
26%
X-Bracing Con. #2
7%
55%
Ground Crewman #3
14%
61%
Ground Crewman #4
0%
81%
Crane Operator #2
0%
30%
Group Percentage
10%
46%
Total Cumulative Time - Column and Pod Beam
Total Cumulative Time - Bar Joists
Total Time
1%
7%
65%
16%
6%
Waste
Extra
Processin
4%
1%
10%
20%
1%
0%
15%
11%
0%
0%
42%
0%
0%
0%
0%
32%
0%
4%
6%
0%
0%
2%
1%
16%
0%
7%
16%
17%
1%
1%
NVAR Sum
2%
13%
19%
24%
2%
3%
57%
21%
Total %
VA +
NVAR %
100%
100%
100%
100%
100%
26%
38%
30%
19%
64%
100%
35%
28%
9:34:00 h:m:s
NVAR
Total %
VA +
NVAR %
0%
0%
1%
5%
15%
0%
31%
100%
100%
100%
100%
100%
100%
100%
37%
29%
32%
45%
29%
16%
47%
7%
100%
34%
Total %
VA +
NVAR %
T.W.S.A
0%
0%
0%
0%
0%
0%
0%
0%
NVAR Sum
Waste
Extra
Processin
T.W.S.A
In Proc. Ins.
14%
66%
11:42:30 h:m:s
21%
NVAR
In Proc. Ins.
T.W.S.A
0%
0%
1%
1%
1%
8%
6%
2%
3%
15%
14%
11%
35%
8%
13%
5%
7%
3%
7%
7%
1%
1%
0%
3%
0%
19%
24%
2%
3%
57%
100%
100%
100%
100%
100%
26%
38%
30%
19%
64%
4%
1%
0%
0%
0%
0%
0%
1%
0%
0%
0%
4%
2%
7%
10%
15%
42%
0%
6%
1%
16%
20%
11%
0%
32%
0%
16%
17%
0%
0%
0%
0%
0%
0%
0%
0%
0%
1%
5%
15%
0%
31%
100%
100%
100%
100%
100%
100%
100%
37%
29%
32%
45%
29%
16%
47%
15%
9%
0%
15%
100%
35%
1%
5%
Cumulative
Time for
various
11:42:30
9:34:00
21:16:30
Number of
members
observed
4
24
% of Total Time
Cycle time
% of Total Time
each steel
for each
element requires
element
2:55:38
55%
47%
0:23:55
45%
6%
6:14:49 Man-Hours for one Bay
Figure C.29: Level Three
Table C.22: Quick Summary of Steel Process
Working Days
37
Working Time
1544 man hours
VA Total
152 man hours
NVAR Total
373 man hours
NVA Total
1018 man hours
224
10%
25%
65%
NVA Time
NVAR Time
1
VA Time
Work Time
0
500
1000
1500
2000
Man-hours
Figure C.30: Quick Summary Graph - One Phase of the Steel Process
Figure C.31 and Table C.23 illustrate how the work distribution values changed and grew
stream map were used to formulate all the VA, NVAR and NVA values in Table C.23. On
Figure C.26, the cumulative NVA hours line grew the fastest compared to the other work
distribution values. The black vertical line (on the left) indicates when the steel delivery and
shakeout processes finished and the PBC process began. The next vertical line indicates the start
of the steel erection process using both crews. The slope change in the cumulative calendar hours
line resulted from additional workers being added to the team between the various stages. This
crew variation affected the data results for the lines shown on Figure C.31.
Table C.23 includes inventory positions; in these positions, the steel was not touched at all.
These inventory days occurred so that the required crews for the erection phase could be gathered
and organized. The crew was under contract with a second subcontractor, while the material for
the job was controlled by the first subcontractor. This highlights how multiple contracts could
affect the value stream. One subcontractor’s goals were not the same as the second. Until the
ultimate goal (value) is defined by the customer, this value stream will not be capable of reaching
its full potential.
Work Distribution
4500
4000
Time (man-hours)
3500
3000
2500
Cumulative VA Hours
Cumulative NVAR Hrs.
2000
Cumulative NVA Hrs
Erection Process
Begins
1500
Stage 1
Finishes
1000
Pod Beams
attached to
Spandrel
500
0
1
3
5
7
9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53
Note: The percentages used to
create this chart are the
average values from the work
distribution values found for the
entire crew.
Calendar Days
Figure C.31: Work Distribution Lifecycle Graph
225
Table C.23: Spreadsheet of Values Used to Create Work Distribution Life Cycle Graph
Stage
Stage 1
Stage 1
Stage 1
Stage 1
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Day
Monday
Tuesday
Steel waits on the ground until erected
Wednesday
Thursday
Pod beam connected to spandle beam on ground
Friday
Weekend
Saturday
Weekend
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Weekend
Saturday
Weekend
Sunday
2 crews erecting structural steel, 1st crew = columns and pod beams, 2nd crew = bar joi Monday
2 crews erecting structural steel, 1st crew = columns and pod beams, 2nd crew = bar joi Tuesday
2 crews erecting structural steel, 1st crew = columns and pod beams, 2nd crew = bar joi Wednesday
2 crews erecting structural steel, 1st crew = columns and pod beams, 2nd crew = bar joi Thursday
2 crews erecting structural steel, 1st crew = columns and pod beams, 2nd crew = bar joi Friday
Weekend
Saturday
Weekend
Sunday
Weekend
Saturday
Weekend
Sunday
Weekend
Saturday
Weekend
Sunday
Weekend
Saturday
Weekend
Sunday
Weekend
Saturday
Weekend
Sunday
Calendar Calendar
Days
Hours
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
24
24
24
24
16
16
16
16
16
16
16
16
16
16
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
96
Cumulative
Cumulative
Hours
Workabl
Crew
Workable Cumulative
VA
NVAR
NVA
VA Cumulative NVAR Cumulative NVA Cumulative
Calendar
Workable
worked
e Days
available
Hours
days
per day
24
1
1
3
8
24
24
0%
20%
80%
0
0
4.8
4.8
19.2
19.2
48
1
2
3
8
24
48
0%
20%
80%
0
0
4.8
9.6
19.2
38.4
72
1
3
3
8
24
72
0%
0%
100%
0
0
0
9.6
24
62.4
96
1
4
3
8
24
96
0%
0%
100%
0
0
0
9.6
24
86.4
112
1
5
2
8
16
112
10%
25%
65%
1.6
1.6
4
13.6
10.4
96.8
128
0
5
2
0
0
112
10%
25%
65%
0
1.6
0
13.6
0
96.8
144
0
5
2
0
0
112
10%
25%
65%
0
1.6
0
13.6
0
96.8
160
1
6
2
8
16
128
10%
25%
65%
1.6
3.2
4
17.6
10.4
107.2
176
1
7
2
8
16
144
10%
25%
65%
1.6
4.8
4
21.6
10.4
117.6
192
1
8
2
8
16
160
10%
25%
65%
1.6
6.4
4
25.6
10.4
128
208
1
9
2
8
16
176
10%
25%
65%
1.6
8
4
29.6
10.4
138.4
224
1
10
2
8
16
192
0%
0%
100%
0
8
0
29.6
16
154.4
240
0
10
2
0
0
192
10%
25%
65%
0
8
0
29.6
0
154.4
256
0
10
2
0
0
192
10%
25%
65%
0
8
0
29.6
0
154.4
352
1
11
12
8
96
288
10%
25%
65%
9.6
17.6
24
53.6
62.4
216.8
448
1
12
12
8
96
384
10%
25%
65%
9.6
27.2
24
77.6
62.4
279.2
544
1
13
12
8
96
480
10%
25%
65%
9.6
36.8
24
101.6
62.4
341.6
640
1
14
12
8
96
576
10%
25%
65%
9.6
46.4
24
125.6
62.4
404
736
1
15
12
8
96
672
10%
25%
65%
9.6
56
24
149.6
62.4
466.4
832
0
15
12
0
0
672
10%
25%
65%
0
56
0
149.6
0
466.4
928
0
15
12
0
0
672
10%
25%
65%
0
56
0
149.6
0
466.4
1024
1
16
12
8
96
768
10%
25%
65%
9.6
65.6
24
173.6
62.4
528.8
1120
1
17
12
8
96
864
10%
25%
65%
9.6
75.2
24
197.6
62.4
591.2
1216
1
18
12
8
96
960
10%
25%
65%
9.6
84.8
24
221.6
62.4
653.6
1312
1
19
12
8
96
1056
10%
25%
65%
9.6
94.4
24
245.6
62.4
716
1408
1
20
12
8
96
1152
10%
25%
65%
9.6
104
24
269.6
62.4
778.4
1504
0
20
12
0
0
1152
10%
25%
65%
0
104
0
269.6
0
778.4
1600
0
20
12
0
0
1152
10%
25%
65%
0
104
0
269.6
0
778.4
1696
1
21
12
8
96
1248
10%
25%
65%
9.6
113.6
24
293.6
62.4
840.8
1792
1
22
12
8
96
1344
10%
25%
65%
9.6
123.2
24
317.6
62.4
903.2
1888
1
23
12
8
96
1440
10%
25%
65%
9.6
132.8
24
341.6
62.4
965.6
1984
1
24
12
8
96
1536
10%
25%
65%
9.6
142.4
24
365.6
62.4
1028
2080
1
25
12
8
96
1632
10%
25%
65%
9.6
152
24
389.6
62.4
1090.4
2176
0
25
12
0
0
1632
10%
25%
65%
0
152
0
389.6
0
1090.4
2272
0
25
12
0
0
1632
10%
25%
65%
0
152
0
389.6
0
1090.4
2368
1
26
12
8
96
1728
10%
25%
65%
9.6
161.6
24
413.6
62.4
1152.8
2464
1
27
12
8
96
1824
10%
25%
65%
9.6
171.2
24
437.6
62.4
1215.2
2560
1
28
12
8
96
1920
10%
25%
65%
9.6
180.8
24
461.6
62.4
1277.6
2656
1
29
12
8
96
2016
10%
25%
65%
9.6
190.4
24
485.6
62.4
1340
2752
1
30
12
8
96
2112
10%
25%
65%
9.6
200
24
509.6
62.4
1402.4
2848
0
30
12
0
0
2112
10%
25%
65%
0
200
0
509.6
0
1402.4
2944
0
30
12
0
0
2112
10%
25%
65%
0
200
0
509.6
0
1402.4
3040
1
31
12
8
96
2208
10%
25%
65%
9.6
209.6
24
533.6
62.4
1464.8
3136
1
32
12
8
96
2304
10%
25%
65%
9.6
219.2
24
557.6
62.4
1527.2
3232
1
33
12
8
96
2400
10%
25%
65%
9.6
228.8
24
581.6
62.4
1589.6
3328
1
34
12
8
96
2496
10%
25%
65%
9.6
238.4
24
605.6
62.4
1652
3424
1
35
12
8
96
2592
10%
25%
65%
9.6
248
24
629.6
62.4
1714.4
3520
0
35
12
0
0
2592
10%
25%
65%
0
248
0
629.6
0
1714.4
3616
0
35
12
0
0
2592
10%
25%
65%
0
248
0
629.6
0
1714.4
3712
1
36
12
8
96
2688
10%
25%
65%
9.6
257.6
24
653.6
62.4
1776.8
3808
1
37
12
8
96
2784
10%
25%
65%
9.6
267.2
24
677.6
62.4
1839.2
3904
1
38
12
8
96
2880
10%
25%
65%
9.6
276.8
24
701.6
62.4
1901.6
4000
1
39
12
8
96
2976
10%
25%
65%
9.6
286.4
24
725.6
62.4
1964
4096
1
40
12
8
96
3072
10%
25%
65%
9.6
296
24
749.6
62.4
2026.4
226
Appendix D
Case Study No. 4 - Process Piping
1.0 Overview
1.1 Project Goal
construction process. During this study, observations focused on the installation of eight-inch
diameter steel pipe. Field data were gathered on two separate value streams: the actual flow of
the pipe from the time it arrived on the jobsite until it was erected into final position, and the flow
of worker activities performed to install the eight-inch diameter steel pipe.
Data collection was accomplished in two consecutive days, with video footage taken during both
sessions. Two different piping crews were observed; each consisted of two pipe fitters. Each
observer was equipped with a digital camera. The digital video cameras were positioned to view
the activity area at right angles to provide “depth” in both viewing directions.
In the lab, two televisions were placed next to each other and used to view the recorded piping
operations. Using both cameras provided a three-dimensional view of the work space for the data
collection process. Each time a new task was started, an entry was made on the data sheet. For
example, an entry might indicate that a worker was grinding a pipe. The next entry might
indicate that the worker had moved to gather the tools or materials necessary to continue prepping
the pipe for installation. The elapsed time for each task was recorded as well as the observer’s
judgment regarding whether the task was value adding (VA), non-value adding (NVA), or nonvalue adding but required (NVAR).
The project involved the installation of an auxiliary boiler in an existing power plant. The
housing for the boiler was located adjacent to the main power plant boiler room. From the
existing structure, four-inch natural gas pipes and eight-inch steam piping were routed from the
existing lines back to the new auxiliary boiler housed in the new structure. The purpose of the
auxiliary boiler is to provide energy to the power plant’s “life systems” when the main boiler is
shut down for maintenance or repair.
Two separate areas were observed for this study. The first area was in the new structure housing
the auxiliary boiler, which was located north of the main power plant facility. The room was
roughly 30 feet wide by 60 feet long and 40 feet high. The focus of the video footage taken in
this area was the erection of an eight-inch pipe spool approximately two feet long, a relief valve
and an eight-inch elbow pipe spool approximately five feet long. All piping components
observed had flanged/bolted connections.
The second area was within the main power plant facility adjacent to the wall between the power
plant facility and the new auxiliary boiler room. The focus of the video footage in this area was
the erection of a pipe elbow piece for the steam line that was to be used to bypass the main boiler
227
steam line. Other work within the same area included placement and welding of a four-inch
natural gas line that was pulled off the main gas line to fire the burner for the auxiliary boiler.
The area of work was located 15 feet above the ground floor on top of temporary scaffolding
erected earlier by a separate carpentry crew. The elbow was constructed with the eight-inch pipe
and was considered a subset of the observed operations that formed part of the overall steps
required to erect the entire steam line. The elbow erection activities were preceded by the
following: cutting the new pipe spool section to the desired length while it was in the material
lay-down yard and installing pipe hangers to hold the pipe in final position within the structure. It
was succeeded by X-ray testing of each weld along the line as well as a pressurized line test to
discover leakage. The material lay-down yard was located 150 to 200 yards away from the final
erection area within the main boiler structure.
2.0 Eight-Inch Spool Erection Process
During both piping operations, few repetitive tasks occurred. A repetitive task was defined as
one in which the worker repeated the same movement or action for every “member” (e.g., one
pipe spool, valve, elbow) that was erected. For example, in a steel erection process, a repetitive
task would include a worker rigging a steel member to the hoist line each time a similar member
was lifted into final position. A repetitive task within the pipe spool erection process was the
physical act of welding. While the weld might not occur in the same position each time, the
process of completing that weld was the same. An activity included all tasks required to erect one
specific member, such as a prefabricated valve, into final position. For the following sections, the
activity cycle started when work began in the area of the spool erection and finished when the
pipe was welded into final place within the entire pipeline. Diagrams 1 through 9 show the
erection of an eight-inch steam line at two separate locations on the line. Diagrams 1 through 4
show the process observed to install the prefabricated components. Diagrams 5 through 9 show
the process observed to install the field fabricated components.
Crew No. 1 - Cycle One
Diagram 1: Existing Pipe and Valve
Diagram 2: Two-Foot Spool Bolted On
Diagram 3: Second Valve Attached
228
Diagram 4: Elbow Spool Bolted On
Crew No. 2 - Cycle Two
Tee
Section
Diagram 6: Elevation View of Existing Pipe
Diagram 5: Plan View of Work Area
Pipe Stands
Diagram 7: Tee Section Removed
Diagram 8: Tee Section Attached to New
Spool
229
Diagram 9: Finished Line
2.1 Erection Process - Data Collection for Cycle No. 1
The erection of a two-foot section of eight-inch diameter pipe was observed with each end having
the following: a flanged (bolted) connection, a release valve with two flanged connections, and a
five-foot long pipe spool with an elbow in which only one end of the spool had a flanged
connection. The opposite end of the spool was later welded to an adjacent pipe spool member.
The observation period started with the positioning of the two-foot pipe spool under its respective
position within the line. A chain fall was used to hoist the pipe spool into position. For each
connection a “greased” gasket was placed between the flange connections. The adjacent
members were then bolted by hand, and an electric torque gun was used to apply the required
torque pressure on the bolt connections. Following the first spool’s erection, a relief valve was
hoisted into position using the chain fall. The connection process was repeated for the flanged
connection as described above. Finally, the five-foot elbow pipe spool was transported from the
material lay-down yard to the work area. It was hoisted into position and its flanged connection
was bolted in a similar fashion as described above. Because of the limited amount of space in the
work area, all of the pipe sections were first stored within the material lay-down yard and
retrieved as required for the erection process. Each of the pipe sections observed during this erection cycle was prefabricated offsite.
2.2 Erection Process - Data Collection for Cycle No. 2
The erection of one eight-foot pipe spool (eight-inch diameter) was observed. During this cycle,
observed activities included the cutting of a previously erected pipe spool that lay adjacent in the
pipeline to where the new pipe spool was to be erected. The final location of the spool was
approximately 15 feet above the floor. Several intermediate steps were required to position the
spool into its final position in the pipeline. The cycle started when the new pipe spool section
was transported from the material lay-down yard to the work area in the main power plant. The
spool was hoisted 15 feet up onto temporary scaffolding using chain falls. The spool was then
placed on temporary bracing while further prep work was completed. The end piece of the previously erected pipe was prepared using a hand-held grinder.
Removal of this section of pipe was required to realign the section at the correct angle for the
steam line to continue inside the power plant. Once removed, the cut section resembled a fire
hydrant with an end cap (nipple drain) at the bottom and an eight-inch open orifice that was
230
connected to the new spool already positioned on temporary bracing. The cut ends, both on the
remaining section of hung pipe and the end piece that was removed, were ground and beveled
prior to re-welding the connection. The end section was attached to the new spool while it
remained on the temporary bracing. Once completed, the entire section of new pipe (new spool
welded to cut section) was positioned into final alignment under the existing hung spool. Tack
welds were completed first to provide stability and alignment between the two spools while the
production weld was completed. The completion of this weld ended the data collection period
and was the end of the cycle.
The erection process for both cycles required a two-man crew. However, the tasks for the two
cycles required different movements and equipment to erect and secure each spool into its final
position. One crewman was required to bolt the connecting members, while the other crewman
was required to install pipe hangers to support the long sections of pipe, as well as weld
connections between the spools. While the crew size was the same for the two cycles, the time
required to perform the separate tasks was not. Therefore, in contrast to the “ideal” highly
repetitive and balanced manufacturing sequence, it would be difficult to design an erection
sequence that balanced the amount of time needed as well as the equipment necessary to
complete each task.
During the observation period, the following materials were installed:
•
One two-foot section of eight-inch diameter steel pipe with two flanged
connections.
•
One release valve.
•
One five-foot section of eight-inch diameter steel pipe with a 90 degree elbow
and one flanged connection.
•
Eight-foot section of eight-inch diameter pipe.
•
Five pipe fitters.
•
Four to five crew personnel.
were developed for each worker and task that describe the time spent on VA, NVA, and NVAR
actions within each cycle.
2.3 Piping Installation Process
In the following subsections, each worker within the crew is referred to by a number. (Refer to
the end of this case study to review the data sheets for Cycle No. 1.) Piping installation with
flanged connections included the following tasks: rigging of the spool/valve to the chain fall,
placing the piping member into final position, preparing and applying the gasket to the spool
connection, bolting the flanged connection and inspecting the finished product. Other minor
231
tasks occurred, but were not recorded. Figure D.1 shows the major tasks required to complete the
prefabricated pipe spool installation. The shaded areas are used to indicate that some tasks took
longer to complete than others, and that those tasks could occur simultaneously with other tasks.
The shaded regions are not intended to show actual task durations (e.g., two days for material
delivery).
Prefabricated Pipe Spool Installation
Process
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Material Delivered to Site (Material Yard)
Transported to Work Area
Piping Member is Rigged for Chain Pull
Piping Member is Hoisted into Place
Final Prep Work (Grinding Flange Area)
Gaskets Greased and Fit Between Members
Bolts Inserted and Hand Tightened
Final Adjustments (Leveling/Inspections)
Bolts Machine Tightened to Specification
Test and Balance Line
Note: This schedule shows process flow. It does not show actual task durations.
Note: Eight inch piping components for this process include: (1) two foot spool, (1) release valve and (1) five foot elbow spool section.
Figure D.1: Schedule for Piping Erection Process with Flanged Connections
Two workers in a piping crew were the main participants involved with installing the various
piping components during this observation period. One other worker was in the area, but his
contributions of time to the work process were minimal.
Worker 1 was involved with the installation of all four piping components erected during the
observation period. His responsibilities included positioning each piping component into final
position, leveling and adjusting pipe segments to correct levels, bolting and final inspections of
the finished product. Table D.1 and Figure D.2 show the VA, NVA and NVAR values for
worker 1. During the piping installation process, worker 1 contributed the majority of his time
(68 percent) to NVA actions. The only VA actions for the worker occurred while applying the
greased gasket to the connection and physically bolting the flanged connection to its adjacent
piping component.
Table D.1: Prefabricated Piping Data for Worker 1
VA
V a lu e A d d in g
V A T o ta l
0 :1 4 :4 6
1 7 .1 7 %
0 :1 4 :4 6
1 7 .1 7 %
0 :2 1 :4 3
0 :0 8 :3 0
0 :0 9 :1 5
0 :1 8 :5 8
2 5 .2 5 %
9 .8 8 %
1 0 .7 6 %
2 2 .0 5 %
0 :5 8 :2 6
6 7 .9 5 %
NVA
W a itin g
E x tra P ro c .
T ra n s p o rt
M o tio n
N V A T o ta l
NV AR
M a t. P o s .
0 :0 1 :0 0
1 .1 6 %
T .W .S .A
0 :0 1 :0 1
0 :1 0 :4 7
1 .1 8 %
1 2 .5 4 %
N V A R T o ta l
0 :1 2 :4 8
1 4 .8 8 %
G r a n d T o ta l
1 :2 6 :0 0
1 0 0 .0 0 %
232
Worker #1
Prefabricated Piping Data - Cycle #1
NVAR TWSA
13%
NVAR In-Process
Inspection
1%
NVAR Material
Positioning
1%
VA
17%
NVA Motion
22%
NVA Waiting
25%
NVA Transport
11%
10%
Figure D.2: Prefabricated Piping Data for Worker 1
Worker 2 was involved with two of the four piping components installed during this observation
period (a five-foot elbow section and release valve component). His responsibilities included the
following: setup and removal of chain fall rigging, greasing and installing gaskets for flanged
connections, placing piping components into final position, final preparation of flanged
connections (filing) and final bolting. Table D.2 and Figure D.3 show the VA, NVA and NVAR
amounts for worker 2. Notice that worker 2 contributed the majority of his time (54 percent) to
NVA actions. The only time contributed to VA actions occurred while applying the greased
gaskets to the flanged connection area and the physical bolting of flanged connections.
Table D.2: Prefabricated Piping Data for Worker 2
VA
W a ste C la s sific a tio n
V a lu e A d d in g
T im e a t Ac tivity
% o f T im e a t Ac tivity
0 :16 :1 0
1 8 .8 0 %
0 :1 6 :1 0
1 8 .8 0 %
0 :20 :5 1
0 :04 :3 0
0 :03 :2 5
0 :17 :3 0
2 4 .2 4 %
5 .2 3 %
3 .9 7 %
2 0 .3 5 %
0 :4 6 :1 6
5 3 .8 0 %
M at. P o s .
0 :16 :4 4
1 9 .4 6 %
In -P ro c e s s In s.
T .W .S .A
0 :01 :4 0
0 :05 :1 0
1 .9 4 %
6 .0 1 %
N V AR T o ta l
0 :2 3 :3 4
2 7 .4 0 %
G ra n d T o ta l
1 :2 6 :0 0
1 0 0 .0 0 %
V A T o ta l
NVA
W a itin g
E x tra P ro c .
T ra n s p o rt
M o tio n
N V A T o ta l
N V AR
233
Worker #2
Prefabricated Piping Data - Cycle #1
NVAR TWSA
6%
NVAR In-Process
Inspection
2%
NVAR Material
Positioning
19%
VA
19%
NVA Waiting
25%
NVA Motion
20%
NVA Extra
Processing
5%
NVA Transport
4%
Figure D.3: Prefabricated Piping Data for Worker 2
2.4 Piping Installation Process - Cycle No. 2 - Welded Connections
As in the previous sections, each worker within the crew is referred to by a number (refer to the
end of this case study to review the data sheets for Cycle No. 2). Piping installation with field
welded connections included the following tasks: rigging the spool/valve to the chain pull,
placing the piping component into final position, cutting the existing hung pipe to remove and
realigning it, beveling each end that would have a production weld, tack welding and producing a
final production weld. Other minor tasks occurred, but were not recorded. Figure D.4 below
shows the major tasks required to complete the prefabricated pipe spool installation. The shaded
areas are used to indicate that some tasks took longer to complete than others, and that those tasks
could occur simultaneously with other tasks. The shaded regions are not intended to show actual
task durations (e.g., two days for material delivery).
Field Fabricated Pipe Spool Installation
Process
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Material delivered to site (Mat. Yard - 1 load)
Pipe is pulled from shipment bundle
Pipe sections are cut to specified spool length
Grinding on both end to create bevel
Production weld made between spools (if needed)
OR: Spool is transported to directly to work area
Spool is positioned into final placement in pipe line
Alignment jigs are secured around spool ends
Tack welds are made to temporarily secure spools
Production weld made between adjacent spools
In-process inspections for production welds
Tack welds are ground out
Finish grinding occurs on outside weld
Test and balance of line (leaks and valve adj.)
Note: this schedule shows process flow. It does not show actual task durations.
Eight inch piping components for this process include: (1) new eight foot pipe spool.
Figure D.4: Schedule for Piping Erection Process with Welded Connections
The crew was composed of two workers (labeled worker 3 and worker 4). The focus of the crew
was the installation of an eight-inch diameter pipe spool. Each worker shared all of the tasks
required to erect the spool. The schedule on Figure D.4 represents the erection of a pipe spool
234
from start to finish in an “ideal situation.” In fact, the following data analysis includes time
attributed to the rework of a previously hung section of pipe. All time contributed to the rework
of this prehung spool (labeled as “hung pipe,” and “cut section” on the data spreadsheet) is
classified as “Extra Processing” (NVA). Worker 3 was involved with two of the following three
activities: new pipe spool erection, hung pipe removal and new pipe spool erection. Worker 4
was involved with all three activities: hung pipe removal, cut section prep work and new pipe
spool erection.
2.4.1 Hung Pipe Spool Removal
Worker 3 was involved with cutting the existing hung spool and positioning the cut section next
to the new pipe spool that was temporarily positioned on stands within the work area. Table D.3
and Figure D.5 show the VA, NVA and NVAR percentages for worker 3. Nearly one hour of
time was dedicated to this process. Of the time spent on the hung pipe, no VA actions occurred,
and 94 percent of the time was classified as NVA. The small amount of time for NVAR actions
came from setting up temporary lighting around the work area and using pipe fitter paper to align
a “cut line” around the hung pipe.
Table D.3: Field Welded Piping Data for Worker 3 - Hung Pipe
Activity Classification Waste Classification Time at Activity % of Time at Activity
NVA
Waiting
0:12:09
21.19%
Extra Proc.
0:18:25
32.12%
Transport
0:06:41
11.66%
Motion
0:16:35
28.92%
NVA Total
0:53:50
93.90%
NVAR
NVAR Total
T.W.S.A.
0:03:30
0:03:30
Grand Total
0:57:20
6.10%
6.10%
100.00%
Worker 4 was involved with the following: cutting the existing hung spool, grinding/beveling the
remaining exposed end of the hung pipe and positioning the cut section next to the new pipe
spool that was temporarily positioned on stands within the work area. Table D.4 and Figure D.6
show the VA, NVA and NVAR percentages for Worker 4. Approximately half an hour was spent
by this worker on the hung section of pipe. The majority of his time was attributed to beveling
(NVA, extra processing) the remaining end of the hung section of pipe to be welded once again to
the cut section with new spool attached. Roughly 94 percent of the time spent was contributed to
NVA actions, leaving 6 percent for NVAR actions.
235
Worker #3 - Previously Hung Pipe
Field Welded Piping Data
NVAR TWSA
6%
NVA Waiting
21%
NVA Motion
29%
NVA Extra
Processing
32%
NVA Transport
12%
Figure D.5: Field Welded Piping Data for Worker 3 - Hung Pipe
Table D.4: Field Welded Piping Data for Worker 4 - Hung Pipe
NVA
Time at Activity
Waiting
Extra Proc.
0:05:21
0:14:07
19.96%
52.67%
Transport
0:05:27
20.34%
Motion
0:00:10
0.62%
0:25:05
93.59%
0:00:30
0:01:13
1.87%
4.54%
NVAR Total
0:01:43
6.41%
Grand Total
0:26:48
100.00%
NVA Total
NVAR
In-Process Ins.
T.W.S.A.
236
Worker #4 - Previously Hung Pipe
NVAR In Process
Inspection
2%
NVAR TWSA
5%
NVA Motion
1%
NVA Waiting
20%
NVA Transport
20%
52%
Figure D.6: Field Welded Piping Data for Worker 4 - Hung Pipe
2.4.2 Cut Section Prep Work
Worker 3 contributed no time to the rework required to prep the cut section for attachment back
to the remaining hung pipe section. The opposite end of the cut section that was to be attached to
the new spool section had already been prepared prior to erection into place in the pipeline.
Worker 4 is involved with the following activities: grinding the same end previously attached to
the hung pipe, beveling the end section to prepare it for production weld, positioning the pipe
onto temporary supports to continue prep work for weld, positioning the cut section next to the
new pipe spool and continually inspecting the spool end to ensure a flush connection for the
production weld. Table D.5 and Figure D.7 show the VA, NVA and NVAR percentages for
worker 4. No VA actions were noted throughout this work process. Worker 4 spent the majority
of his time on rework activities such as grinding and beveling the connection point in preparation
for the final production weld between the “cut section” and the “previously hung pipe.” NVAR
actions occurred when the worker rigged and positioned the cut section next to the new pipe spool
to complete the production weld (20 percent).
Table D.5: Field Welded Piping Data for Worker 4 - Cut Section
NVA
Time at Activity
Waiting
Extra Proc.
0:08:49
0:38:21
13.49%
58.68%
Transport
0:04:24
6.73%
Motion
0:00:47
1.20%
0:52:21
80.11%
0:05:51
0:07:09
8.95%
10.94%
NVAR Total
0:13:00
19.89%
Grand Total
1:05:21
100.00%
NVA Total
NVAR
Mat. Pos.
T.W.S.A.
237
Worker #4 - Cut Section
NVAR TWSA
NVA Material 11%
NVA Waiting
13%
Positioning
9%
NVA Motion
1%
NVA Transport
7%
NVA Extra
Processing
59%
Figure D.7: Field Welded Piping Data for Worker 4 - Cut Section
2.4.3 New Pipe Spool
Worker 3 was involved with the following activities: aligning/leveling the new pipe spool to the
level of the cut section of pipe, securing pipe alignment guides and inspecting tack welds and production welds. In addition, worker 3 positioned the entire welded component (both the new pipe
spool and cut section as one piece) under the hung pipe and completed a production weld between
the new spool section and hung pipe. Table D.6 and Figure D.8 show the VA, NVA and NVAR
percentages for worker 3. Notice the VA actions in the process. VA levels increased to more
than 20 percent of the total time attributed to the new spool. There was still a large portion of
waste, 54 percent, which highlights an area for improvement in the overall process.
Table D.6: Field Welded Piping Data for Worker 3 - New Spool Section
Ac tiv ity C la ss ific a tio n
VA
W a s te C la s sific a tio n
V a lu e A d d in g
0 :4 3 :1 1
2 0 .3 7 %
0 :4 3 :1 1
2 0 .3 7 %
0 :4 1 :4 9
0 :0 5 :4 3
0 :2 5 :1 5
0 :4 1 :2 5
1 9 .7 2 %
2 .7 0 %
1 1 .9 1 %
1 9 .5 4 %
1 :5 4 :1 2
5 3 .8 7 %
0 :3 1 :2 0
0 :0 9 :0 9
0 :1 4 :0 8
1 4 .7 8 %
4 .3 2 %
6 .6 7 %
N V AR T o ta l
0 :5 4 :3 7
2 5 .7 6 %
G ra n d T o ta l
3 :3 2 :0 0
1 0 0 .0 0 %
V A T o ta l
NVA
W a itin g
E x tra P ro c .
T ra n s p o rt
M o tio n
N V A T o ta l
N V AR
M a t. P o s .
T .W .S .A .
238
Worker #3 - New Spool
NVAR TWSA
7%
NVAR In-Process
Inspection
4%
VA
20.4%
NVAR Material
Positioning
15%
NVA Waiting
20%
NVA Extra
Processing
3%
NVA Motion
20%
NVA Transport
12%
Figure D.8: Field Welded Piping Data for Worker 3 - New Spool Section
Worker 4 was involved with the following: aligning/leveling the new pipe spool to the same
height as the cut section of pipe, securing pipe alignment guides, inspecting tack welds and
production welds, positioning the entire welded component (including both the new pipe spool
and cut section as one piece) under the hung pipe and grinding sections of the production weld
created by worker 3 to ensure a quality production weld. Table D.7 and Figure D.9 show the VA,
NVA and NVAR percentages for worker 4. Notice that worker 4 contributed no VA actions to
the process. The majority of his time was spent waiting while worker 3 created the production
weld.
Table D.7: Field Welded Piping Data for Worker 4: - New Spool Section
NVA
Time at Activity
Waiting
Extra Proc.
1:23:49
0:08:21
47.31%
4.71%
Transport
0:22:24
12.64%
Motion
0:19:43
11.13%
2:14:17
75.79%
0:32:00
0:03:40
0:07:14
18.06%
2.07%
4.08%
NVAR Total
0:42:54
24.21%
Grand Total
2:57:11
100.00%
NVA Total
NVAR
Mat. Pos.
In-Process Ins.
T.W.S.A.
239
Worker #4 - New Spool
NVAR TWSA
4%
NVAR In-Process
Inspection
2%
NVA Waiting
47%
NVAR Material
Positioning
18%
NVA Motion
11%
NVA Transport
13%
NVA Extra
Processing
5%
Figure D.9: Field Welded Piping Data for Worker 4 - New Spool Section
3.0 Results for the Crew
A work distribution chart (Figure D.10) depicts the time spent on various activities for the
prefabricated pipe with flange connection process (Cycle No. 1). Figure D.11 represents work
distribution amounts for the field fabricated pipe spool process (Cycle No. 2). During the
observation period, the erection of four “new” piping components was observed. Each of these
components varied in size and shape and required different equipment and erection procedures.
No similar cycle occurred during the observation. Therefore, “one cycle” was defined as the
entire period of observation. For example, Cycle No. 1 started with the “finish” installation of a
two-foot spool section and concluded when the bolts were tightened around the flanged connection for the five-foot spool section. The different shading on the chart represents the VA and
waste tasks for each worker.
3.1 Crew Composition for Prefabricated Steel Pipe Erection
(Cycle No. 1)
Each worker contributed similar amounts of time to each of the categories, as shown on
Figure D.10. There was a difference at the bottom of the chart because worker 1 was more
involved with extra processing, transportation and equipment requirements (extra prep work on
the end connection, tool gathering and rigging setup). Worker 2 was responsible for the majority
of material positioning. Both workers spent most of their time on waiting and wasted movement.
240
Worker Task Breakdown - Pre-fabbed Pipe
Cycle #1
1:26:24
1:23:31
1:20:38
1:17:46
Value Adding
0:14:46
1:14:53
Mat. Pos .
0:01:00
1:12:00
1:09:07
1:06:14
1:03:22
Value Adding
0:16:10
T.W.S.A
0:10:47
In-Proces s Ins .
0:01:01
Mat. Pos .
0:16:44
1:00:29
0:57:36
0:54:43
0:51:50
Trans port
0:09:15
In-Proces s Ins .
0:01:40
Time(h,m,s)
0:48:58
0:46:05
0:43:12
Value Adding
T.W.S.A
0:05:10
Transport
0:03:25
Extra Proc.
0:04:30
Extra Proc.
0:08:30
0:40:19
0:37:26
0:28:48
In-Process Ins.
T.W.S.A
Transport
Extra Proc.
Waiting
0:34:34
0:31:41
Mat. Pos.
Motion
Waiting
0:21:43
Waiting
0:20:51
0:25:55
0:23:02
0:20:10
0:17:17
0:14:24
0:11:31
0:08:38
Motion
0:18:58
Motion
0:17:30
Worker # 1
Worker # 2
0:05:46
0:02:53
0:00:00
Figure D.10: Work Distribution Chart - Cycle No. 1
3.2 Crew Composition for Field Fabricated Steel Pipe Erection
(Cycle No. 2)
Figure D.11 shows that worker 3 contributed the only VA time to the erection of the new spool.
All of worker 4’s actions were NVA and NVAR. Worker 4 waited for more than one and a half
of the four and a half hours observed. A large amount of waiting occurred while worker 3
beveled and welded each connection. Each worker contributed similar amounts of time to the
following: material positioning, temporary work and support activities, in-process inspections,
and transportation actions. Worker 4 contributed a large portion of his time to extra processing.
This included recutting the hung pipe, grinding and beveling each cut end and extra preparation
work that was required to fix the defect.
241
Worker Task Breakdown - Field Fabricated
Cycle #2
4:48:00
4:40:48
4:33:36
4:26:24
4:19:12
4:12:00
4:04:48
Mat. Pos.
0:37:51
Value Adding
0:43:11
3:57:36
In-Process Ins
0:04:10
3:50:24
3:43:12
3:36:00
3:28:48
T.W.S.A.
0:15:36
Mat. Pos.
0:31:20
3:21:36
In-Process Ins. Transport
0:32:15
0:09:09
3:14:24
3:07:12
3:00:00
2:52:48
T.W.S.A.
0:17:38
Value Adding
Tim
e(h,m
,s)
2:45:36
2:38:24
2:31:12
Mat. Pos.
Transport
0:31:56
Extra Proc.
1:00:49
2:24:00
2:02:24
T.W.S.A.
Transport
2:16:48
2:09:36
In-Process Ins.
Extra Proc.
Extra Proc.
0:24:08
Waiting
Motion
1:55:12
1:48:00
1:40:48
1:33:36
1:26:24
1:19:12
Waiting
0:53:58
Waiting
1:37:59
1:12:00
1:04:48
0:57:36
0:50:24
0:43:12
0:36:00
0:28:48
Motion
0:58:00
0:21:36
0:14:24
Motion
0:20:40
0:07:12
0:00:00
Worker 3
Worker 4
Figure D.11: Work Distribution Chart - Cycle No. 2
During the observation period for Cycle No. 1, no rework occurred. The erection work involved
for the three different piping components appeared to be assigned equally to each worker.
However, the time contributed to wasted motion, transport and waiting highlights areas in which
crew efficiency could be improved.
During the observation period for Cycle 2, a significant portion of the time attributed to the erection of the new pipe spool involved rework. The limited work space inhibited movement and
affected the ease in which the spool was erected. In addition, incidences occurred in which
workers had to share equipment, which resulted in higher waiting times. Finally, several
movements were attributed to gathering new grinding pads and welding rods that were scattered
around the work area.
242
A goal of this report was to examine and document the inefficiencies in construction operations.
In general terms, inefficiencies were classified as the following three types: inefficiency due to
waste (NVA activities), inefficiency due to unnecessary work (excessive NVAR activities) and
inefficiency due to poorly designed work processes (ineffective VA activities). The following
section identifies opportunities for process improvement by applying Ohno’s (1988) seven wastes
in production and then evaluating the production process against a more comprehensive set of
lean principles.
Tables D.8 and D.9 list the subset of activities specific to each crew that occurred to accomplish
the entire erection process. The NVA category is further divided into the time spent in the waiting, extra processing, transport and movement categories. Additionally, NVAR is broken down
into its three subcategories to clarify how time was spent within observed cycles.
Table D.8: Crew No. 1 Subactivities
Prefabricated Pipe: Two-Foot Spool
Total Cumulative Time Spent on Spool 0:02:55 h:m:s
VA
Waste
NVAR
Crew Member
Material In Proc.
Extra
All
Transport Movement
TWSA
Waiting
Total
Pos.
Ins.
Processing
Activities
Worker #1
48%
10%
0%
28%
0%
0%
14%
0%
100%
0%
0%
0%
0%
0%
0%
0%
0%
0%
Worker #2
VA +
NVAR
62%
0%
Group Percentage
0%
48%
10%
0%
28%
0%
0%
14%
62%
100%
Prefabricated Pipe: Release Valve
Total Cumulative Time Spent on Release Valve 0:36:50 h:m:s
VA
Waste
.
VA +
Crew Member
All
Extra
Material In Proc.
Waiting
Transport Movement
Total NVAR
TWSA
Activities
Processing
Pos.
Ins.
Worker #1
9%
58%
0%
11%
0%
0%
0%
22%
100%
31%
30%
12%
0%
11%
10%
25%
6%
6%
100%
67%
Worker #2
Group Percentage
25%
21%
0%
11%
8%
20%
5%
10%
100%
Prefabricated Pipe: Elbow Spool
Total Cumulative Time Spent on Spool 2:04:44 h:m:s
Waste
NVAR
VA
Crew Member
Extra
Material In Proc.
All
Total
Waiting
Transport Movement
TWSA
Activities
Processing
Pos.
Ins.
Worker #1
14%
24%
12%
9%
27%
2%
0%
12%
100%
13%
30%
8%
0%
26%
17%
0%
6%
100%
Worker #2
Group Percentage
13%
28%
10%
6%
243
26%
8%
0%
9%
100%
60%
VA +
NVAR
28%
36%
30%
Table D.9: Crew No. 2 Subactivities
1:05:21 h:m:s
Field Welded - Cut Section
Total Cumulative Time Spent on Section
VA
Waste
NVAR
All
Extra
Material In Proc.
Crew Member
Total
Activities Waiting Processing Transport Movement Pos.
Ins.
TWSA
0%
0%
0%
0%
0%
0%
0%
0%
0%
Worker #3
Worker #4
0%
13%
59%
7%
1%
9%
0%
11%
100%
Group
Percentage
0%
13%
1%
9%
0%
11%
100%
59%
7%
Field Welded - Hung Pipe
1:24:08 h:m:s
Total Cumulative Time Spent on Pipe
VA
Waste
NVAR
Crew Member
All
Extra
Material In Proc.
Total
Ins.
TWSA
Worker #3
0%
21%
32%
12%
29%
0%
0%
6%
100%
0%
20%
53%
19%
1%
0%
2%
5%
100%
Worker #4
Group
Percentage
0%
21%
39%
14%
19%
0%
1%
6%
100%
6:29:11 h:m:s
Field Welded - New Pipe Spool
Total Cumulative Time Spent on Spool
VA
Waste
NVAR
All
Extra
Material In Proc.
Crew Member
Total
Ins.
TWSA
Worker #3
20%
20%
3%
12%
20%
15%
4%
7%
100%
Worker #4
0%
47%
5%
13%
11%
18%
2%
4%
100%
Group
11%
32%
4%
12%
16%
16%
3%
5%
100%
Percentage
VA +
NVAR
0%
20%
20%
VA +
NVAR
6%
7%
7%
VA +
NVAR
46%
24%
36%
Table D.10 shows the weighted averages for the observed processes. These averages were used
to represent the piping process in its entirety for this specific case study.
Table D.10: Summary Table for Piping Process - Weighted Averages
Pipe Spools - Entire Process
Pre-Fabbed Pipe: Entire Process
VA
Crew Member
All Activities
Worker #1
17%
Worker #2
19%
Field Welded - Entire Process
Worker #3
16%
Worker #4
0%
Weighted Average
Percentages for
10%
Group
Waiting
25%
25%
20%
36%
27%
Total Cumulative Time Observed for all Process
11:50:40 h:m:s
6:52:15 h:m:s
Waste
NVAR
Total %
Extra
Transport Movement Material Pos. In Proc. Ins. T.W.S.A
Processing
10%
11%
22%
3%
1%
11%
100%
5%
4%
20%
19%
2%
6%
100%
2:39:49 h:m:s
9%
12%
22%
12%
3%
7%
100%
23%
12%
8%
14%
2%
6%
100%
14%
11%
16%
12%
2%
7%
100%
VA + NVAR %
32%
46%
38%
21%
32%
4.1.1 Waiting
Waiting accounted for roughly one third of the total time observed during each cycle shown in
Tables D.8 and D.9. For the two dominant tasks of each cycle (elbow spool erection for Cycle
No. 1 and new pipe spool erection for Cycle No. 2), a consistent one third of total time was
wasted waiting. Waiting periods are nearly identical for each member within Crew No. 1.
Table D.9 shows that for the Field Welded – New Pipe Spool activity, worker 4 waited twice as
long as worker 3. This variation in waiting was because only one worker was able to weld the
connection at any specific time.
244
Tables D.8 and D.9 show waste due to excess motion for both crews. The work areas were
limited in size, which prevented the workers from storing material around the work area. For
example, for Cycle No. 1, there was a 21 percent overall waste percentage. For each piping
component, one worker had to walk to the material lay-down yard to retrieve and transport that
component back to the work area. For Cycle No. 2, a smaller value for motion was recorded –
15 percent of the total time. The majority of the time wasted on motion came from workers
walking around the platform looking for tools/material necessary to continue their work.
Interpretation of this category included the use of defective materials delivered onsite that
required modification to be operable. This included any preparation work around connection
points such as cleaning out any metal slag from the spool, beveling and grinding the end connections prior to welding them and all preparation work required for the bolts prior to insertion into
the bolt holes. This type of extra preparation work on the flanged connections accounted for the
extra processing time spent during Cycle No. 1. During Cycle No. 2, rework (extra processing)
accounted for over 16 percent of the total time attributed to the piping process. Worker 4 devoted
more than 50 percent of his time to cutting, beveling and reconnecting the defective hung section
of pipe.1
Several instances were observed in which equipment and material had to be rehandled and moved
into an accessible position for the installation process. Transportation absorbed roughly 12 percent of each worker’s time during the cycles observed. A large portion of the time attributed to
transportation involved positioning piping components from the lay-down yard into their holding
position below the “final pipeline.” However, it was the small movements contributed by each
worker while looking for tools and equipment that added large amounts of time to this waste
category. Transport waste also occurred during Cycle No. 2 during positioning of the pipe on top
of pipe stands to further prepare the new pipe spool for installation into final position in the line.
4.2.1 Overproduction/Work in Progress (WIP)
this study, WIP was represented by the unfinished pipeline.
1
Note: This differed from the waste category defects discussed in Section 4.2 in that the current
crew was responsible for erecting the hung pipe incorrectly. The defect was not passed downstream to the next work station, but was reworked by the existing crew.
245
4.2.2 Inventory
Material deliveries were made continually throughout the construction process. The steel pipe
was delivered onsite on a large flatbed and placed within the material lay-down yard in bundles of
similar pipe. The material was then moved to the tent for field fabrication or, when possible, it
was moved directly to its position within the pipeline. The material was retrieved from the pipe
bundles as needed. The variability of the amount of material onsite was heavily influenced by the
sporadic nature of the pipe erection process. The limited area within the structure where the
installation occurred created a problem for the erection crew to install the pipeline in linear order.
Due to the brief observation time period onsite, it was difficult to quantify the inevitable waste in
inventory that occurred.
4.2.3 Defects
the part of a crew or a follow-up crew. A defective release valve or piping component delivered
onsite from the manufacturer is an example of a defect (i.e., the material has been passed downstream through the value stream to the next work station). Another example of a defect is
included in the punch list process at the end of a job. When a defect in the finished product is
found at this stage, a separate follow-up crew is activated to correct the defect. Hence, the defect
is pushed onto the next work station. Time associated with the crew members having to rework
the hung pipe section was accounted for in the Extra Processing column shown in Table D.10.
Furthermore, because of the brief site visit, no waste due to defects was observed.
The following paragraphs describe the current value stream map for this piping erection process,
beginning from the time material was ordered and shipped from the manufacturer, through the
construction production process and ending with the material in final position within the facility.
Figure D.12 is a simple flow diagram, with each box representing a point in time when the material was handled, either to be moved or transformed into its next stage (phase) in the construction
life cycle.
Manufacturer
delivers
material to
site in one
large
shipment
Pipe spool is
pulled from
bundle and
transported to
work area
Material is
delivered to
material laydown yard in
piping bundles
Pipe spool is
pulled from
bundle to be
field fabricated
to specified
requirement
Spool is erected
and secured into
final position
Spool positioned in
work area beneath
installation point
Fabricated spool
is transported to
work area
Final prep
work is
performed
on spool
Figure D.12: Material Flow Diagram
Information on delivery and handling of the piping components was obtained from the project
manager. Once it arrived onsite, the basic flow of the steel pipe was as follows:
•
Post-piping components were delivered to the site in bundles to the lay-down
yard.
•
Raw pipe was pulled from the separate bundles in the yard.
246
•
Pipe was cut to desired length.
•
Pipe followed one of two paths after being cut:
−
Pipe was welded to other pipe sections while remaining in the tent inside
the material lay-down yard.
(1)
−
Entire spool was moved to final location for installation.
Pipe was erected into intended location within the power plant.
•
Pipe was welded at joints.
•
Pipe was X-rayed following erection:
−
Pass - Finished for painting.
−
Fail - Weld was cut out and welded again:
(1)
Pass - Finished for painting.
5.1 Value Stream Map for Case Study No. 4
For the value stream map analysis depicted on Figure D.13, three levels were needed to represent
material must go through to reach finished state. Each time material was moved or transformed, a
stage box is used to represent the process. Some of the stages include substages (Level Two) to
The value stream map shown on Figure D.13 was created using the information described in the
preceding section. Each major stage that the piping components went through is represented on
Level One. Two different manufacturers were used to supply piping components to the job and
are represented in this map. Ideally, the material should be tracked separately; however, lack of
information prevented this from occurring. During Stage Two, the components went through two
substages to complete the main stage. Notice that the steel had inventory position here, which
represented the time that the steel sat between fabrication and erection.
Stage One of the value stream was not observed during this site visit. However, the project
superintendent confirmed that Stage One occurred. An estimate of three days’ total was shown
for Stage One completion. This value stream ended once the piping erection process reached the
testing and detailing stage. Again, the brief observation period prevented acquiring data about
this stage in the entire steel erection process.
Attention was instead focused on the two substages required for Stage Two. As shown in
Levels Two and Three, the majority of time spent during the steel erection process was on the
field fabricated spools. Furthermore, the total linear footage required to be field fabricated and
prefabricated was estimated in Area Three of Level Three. Using this value and the value found
for cumulative time spent per linear foot of pipe, the man-hours required to complete each line
(field or prefabricated process) were estimated. These values were used to determine the total
“Days required” for the main substages in Level Two. Refer to the circled areas on Figure D.13;
these values are subject to change with actual data entered in the Estimated Total Linear Feet for
Each Pipe column.
247
Every 1-3 days
Production Control
Project Engineer
Level One
Distribution of time from VSM for entire process
Project Feedback
Triggering Event
Steel Is ordered in one large shipment
Percent Complete
NVA Time
Pipe Component (valves, flangeplates, etc…) Supplier
Pipe Spool Supplier
Spools are in place awaiting final
testing and detailing.
As Required
NVAR Time
1
VA Time
Work Time
Daily
0
Spools are delivered to
the site in bundles of like
sizes in standard lengths.
O
O
200
400
Pipe components are shipped to
material yard on the site
O
O
O
600
800
1000
1200
Manhours
O
O
Stage One - Spools and Pipe
Components are Offloaded from
Trucks and positioned in material
yard
Days required
3
Equipment involved:
Forklift
1
Workers involved
4
Crew
WT
VA ( 0%)
NVAR (0%)
NVA (100%)
O
96
0
0
96
Stage Two - Pipe Elements (Raw
Spools, Valves, etc…) Are Pulled
from Material Yard, Prepped, and
Erected into Final Position.
Days required
30
Equipment involved:
0
Workers involved
Crew
9
WT
720.0
VA ( 8%)
61.5
NVAR (19%)
151.6
NVA (73%)
506.9
Inv
Observation Period
Working Days
33
Working Time
1267
man hours
VA Total
98
man hours
NVAR Total
266
man hours
NVA Total
904
man hours
Inventory Days
22
20
Level Two
14.1
Level Three
4
451.2
36.1
94.7
320.3
Crew #2: Field Welded - Entire Process
VA
Crew Member
All Activities
Waiting
Worker #3
Worker #4
Group Percentage
16%
0%
20%
36%
8%
28%
In
v
2
All Activities
Waiting
25%
25%
17%
25%
NVA
VA
All Activities
Worker #1
Worker #2
Field Welded - Entire Process
Worker #3
Worker #4
Weighted Average
Percentages for
Group
Waiting
17%
19%
25%
25%
16%
0%
20%
36%
10%
Cumulative Time for Field Fabricated
Cumulative Time for Piping Components
Total Time
1.8
0
3
43.2
7.3
9.5
26.4
8:58:40
12%
12%
12%
71%
Extra
Processing
10%
5%
Movement
Material Pos.
22%
8%
12%
14%
15%
13%
NVAR
27%
14%
Linear Feet
of Various
Spools
8
8
In Proc. Ins.
3%
2%
2%
TWSA
Total
7%
6%
100%
100%
38%
21%
100%
30%
6%
Transport
11%
4%
Movement
11%
Material Pos.
22%
20%
16%
Estimated Total
Cumulative
Linear Feet for
Time Spent
Each Pipe
Per Linear Foot
1:07:20
100
0:21:30
20
Total Estimated Mhrs
21%
2:52:00
h:m:s
In Proc. Ins.
3%
19%
1%
2%
11%
2%
NVAR
TWSA
Total
VA + NVAR
11%
6%
100%
100%
32%
46%
100%
39%
9%
22%
11:50:40
6:52:15
h:m:s
h:m:s
NVAR
Material Pos.
In Proc. Ins.
3%
19%
1%
2%
12%
14%
3%
2%
12%
Estimated Man-hours
to Complete Each
Line
112:13:20
7:10:00
119:23:20
2%
% of Total
Time
94%
6%
TWSA
11%
6%
2:39:49
7%
6%
7%
Total
Figure D.13: Value Stream Map
VA + NVAR
100%
100%
h:m:s
100%
100%
38%
21%
32%
46%
100%
32%
% of Total
Time each LF
of Pipe Spool
0.9%
0.3%
248
VA + NVAR
NVAR
8%
7%
21%
61%
Total Cumulative Time Observed for all Process
Waste
Extra
Transport
Movement
Processing
10%
11%
22%
5%
4%
20%
9%
12%
22%
23%
12%
8%
Cumulative
Time Observed
for Various
8:58:40
2:52:00
11:50:40
h:m:s
NVAR
Transport
16%
Pipe Spools - Entire Process
Prefabricated Pipe: Entire Process
Crew Member
676.8
54.1
142.1
480.5
Waste
17%
19%
Group Percentage
6
Total Cumulative Time Spent on Column
NVA
Crew Member
0
Waste
Extra
Processing
9%
23%
Prefabricated Pipe: Entire Process
VA
Worker #1
Worker #2
Final Preparation for Piping
Components and Final Bolt-Up
Days required
Equipment involved:
Handtools
Workers involved:
Crew
WT
VA ( 17%)
NVAR (22%)
NVA (61%)
28.2
Final Preparation for Onsite
Fabricated Spools and their
Installation
Days required
14.1
Equipment involved:
Handtools
0
Workers involved:
Crew
2
WT
225.6
VA ( 8%)
18.0
NVAR (21%)
47.4
NVA (71%)
160.2
Raw Spools Are Pulled from Bundles
and Fabricated Onsite to Specified
Dimensions
Days required
Equipment involved:
Handtools
Workers involved:
Crew
WT
VA ( 8%)
NVAR (21%)
NVA (71%)
Pipe Spools Fabricated Onsite
Days required
Equipment involved:
Handtools
Workers involved:
Crew
WT
VA ( 8%)
NVAR (21%)
NVA (71%)
10%
21%
68%
1400
Another substage process was required for the field fabrication process in Level Two. The spools
were fabricated in a temporary shop designated the “tent.” Four crewmen were entered into this
substage to represent the average number of pipe fitters working in the tent. It was assumed that
the weighted average values found from the observations were representative of the work
distribution values for this substage.
Table D.11 and Figure D.14 show the Quick Summary results for the work distribution values.
Of the 1,267 total workable hours committed to the piping erection process, only 98 of them were
VA. The NVAR category consisted of 266 hours; this value was high as a result of moving the
pipe 15 feet above the ground floor. Finally, the majority of time spent during the piping erection
process was on NVA actions.
Table D.11: Quick Summary of Steel Process
Observation Period
Working Days
33
Working Time
1,267
Man-hours
98
Man-hours
VA Total
NVAR Total
266
Man-hours
904
Man-hours
NVA Total
Distribution of Time from VSM for Entire Process
NVA Time
NVAR Time
1
VA Time
Work Time
0
200
400
600
800
1000
1200
1400
Man-hours
Figure D.14: Graphic Display for the Quick Summary Table
Figure D.15 and Table D.12 illustrate how the work distribution values changed and grew
stream map were used to formulate all the VA, NVAR and NVA values in Table D.12. As shown
on Figure D.15, the cumulative NVA hours line grew the fastest compared to the other work
distribution values. The black vertical line indicates when the pipe delivery process finished and
the steel erection process began. The slope change for the cumulative work hours line indicates
that more crew members were introduced to the process. As seen on the figure, the cumulative
VA hours line finally started to grow.
249
4000
3500
Time (man-hours)
3000
2500
Cumulative Workable Hours
2000
Cumulative VA Hours
Cumulative NVAR Hours
1500
1000
Fabrication and Installation
Begin
500
Note: The values used to create
this chart are the average
values from the work
entire crew.
0
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
Calendar Days
Figure D.15: Work Distribution Life Cycle Graph
250
Table D.12: Spreadsheet of Values Used to Create Work Distribution Life Cycle Graph
Stage
Day
Stage 1
Stage 1
Stage 1
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Stage 2
Steel is delivered and offloaded from Paint Subcontractor
Piping Components are fabbed onsite, prepped and
Weekend
Weekend
Weekend
Weekend
Weekend
Weekend
Weekend
Weekend
Weekend
Weekend
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Cumulative
Cumulative
Hours
Calendar Cumulative Calendar
Workable
Crew
Workable Cumulative
VA
NVAR
NVA
Calendar
Workable
worked
Days Calendat Days Hours
Days
available
Hours
days
per day
1
1
32
32
1
1
4
8
32
32
0%
20%
80%
0
0
6.4
6.4
25.6
25.6
1
2
32
64
1
2
4
8
32
64
0%
20%
80%
0
0
6.4
12.8
25.6
51.2
1
3
32
96
1
3
4
8
32
96
0%
20%
80%
0
0
6.4
19.2
25.6
76.8
1
4
88
184
1
4
11
8
88
184
10%
21%
68%
8.8
8.8
18.48 37.68
59.84 136.64
1
5
88
272
1
5
11
8
88
272
10%
21%
68%
8.8
17.6
18.48 56.16
59.84 196.48
1
6
88
360
0
5
11
0
0
272
10%
21%
68%
0
17.6
0
56.16
0
196.48
1
7
88
448
0
5
11
0
0
272
10%
21%
68%
0
17.6
0
56.16
0
196.48
1
8
88
536
1
6
11
8
88
360
10%
21%
68%
8.8
26.4
18.48 74.64
59.84 256.32
1
9
88
624
1
7
11
8
88
448
10%
21%
68%
8.8
35.2
18.48 93.12
59.84 316.16
1
10
88
712
1
8
11
8
88
536
10%
21%
68%
8.8
44
18.48 111.6
59.84
376
1
11
88
800
1
9
11
8
88
624
10%
21%
68%
8.8
52.8
18.48 130.08
59.84 435.84
1
12
88
888
1
10
11
8
88
712
10%
21%
68%
8.8
61.6
18.48 148.56
59.84 495.68
1
13
88
976
0
10
11
0
0
712
10%
21%
68%
0
61.6
0
148.56
0
495.68
1
14
88
1064
0
10
11
0
0
712
10%
21%
68%
0
61.6
0
148.56
0
495.68
1
15
88
1152
1
11
11
8
88
800
10%
21%
68%
8.8
70.4
18.48 167.04
59.84 555.52
1
16
88
1240
1
12
11
8
88
888
10%
21%
68%
8.8
79.2
18.48 185.52
59.84 615.36
1
17
88
1328
1
13
11
8
88
976
10%
21%
68%
8.8
88
18.48
204
59.84
675.2
1
18
88
1416
1
14
11
8
88
1064
10%
21%
68%
8.8
96.8
18.48 222.48
59.84 735.04
1
19
88
1504
1
15
11
8
88
1152
10%
21%
68%
8.8
105.6 18.48 240.96
59.84 794.88
1
20
88
1592
0
15
11
0
0
1152
10%
21%
68%
0
105.6
0
240.96
0
794.88
1
21
88
1680
0
15
11
0
0
1152
10%
21%
68%
0
105.6
0
240.96
0
794.88
1
22
88
1768
1
16
11
8
88
1240
10%
21%
68%
8.8
114.4 18.48 259.44
59.84 854.72
1
23
88
1856
1
17
11
8
88
1328
10%
21%
68%
8.8
123.2 18.48 277.92
59.84 914.56
1
24
88
1944
1
18
11
8
88
1416
10%
21%
68%
8.8
132
18.48 296.4
59.84
974.4
1
25
88
2032
1
19
11
8
88
1504
10%
21%
68%
8.8
140.8 18.48 314.88
59.84 1034.24
1
26
88
2120
1
20
11
8
88
1592
10%
21%
68%
8.8
149.6 18.48 333.36
59.84 1094.08
1
27
88
2208
0
20
11
0
0
1592
10%
21%
68%
0
149.6
0
333.36
0
1094.08
1
28
88
2296
0
20
11
0
0
1592
10%
21%
68%
0
149.6
0
333.36
0
1094.08
1
29
88
2384
1
21
11
8
88
1680
10%
21%
68%
8.8
158.4 18.48 351.84
59.84 1153.92
1
30
88
2472
1
22
11
8
88
1768
10%
21%
68%
8.8
167.2 18.48 370.32
59.84 1213.76
1
31
88
2560
1
23
11
8
88
1856
10%
21%
68%
8.8
176
18.48 388.8
59.84 1273.6
1
32
88
2648
1
24
11
8
88
1944
10%
21%
68%
8.8
184.8 18.48 407.28
59.84 1333.44
1
33
88
2736
1
25
11
8
88
2032
10%
21%
68%
8.8
193.6 18.48 425.76
59.84 1393.28
1
34
88
2824
0
25
11
0
0
2032
10%
21%
68%
0
193.6
0
425.76
0
1393.28
1
35
88
2912
0
25
11
0
0
2032
10%
21%
68%
0
193.6
0
425.76
0
1393.28
1
36
88
3000
1
26
11
8
88
2120
10%
21%
68%
8.8
202.4 18.48 444.24
59.84 1453.12
1
37
88
3088
1
27
11
8
88
2208
10%
21%
68%
8.8
211.2 18.48 462.72
59.84 1512.96
1
38
88
3176
1
28
11
8
88
2296
10%
21%
68%
8.8
220
18.48 481.2
59.84 1572.8
1
39
88
3264
1
29
11
8
88
2384
10%
21%
68%
8.8
228.8 18.48 499.68
59.84 1632.64
1
40
88
3352
1
30
11
8
88
2472
10%
21%
68%
8.8
237.6 18.48 518.16
59.84 1692.48
251
Appendix E
1.0 Overview
1.1 Project Goal
construction process. During this study, observations were focused on the installation of an eightinch diameter pipe spool. Two 10-foot sections of eight-inch diameter pipe were joined on the
ground to form the spool. Work was observed on two-inch diameter and four-inch diameter
spools, and a 10-inch diameter prefabricated elbow section. Field data collected on two separate
value streams included the actual flow of the prefabricated pipe from the time it arrived on the
jobsite until it was erected into final position, and the flow of worker activities performed to
install the several sections of steel pipe.
Data collection was accomplished in two consecutive days, with video footage taken during both
sessions. One crew consisting of three men was observed during both days. Each observer was
equipped with a digital camera. The digital video cameras were positioned to view the activity
area at right angles to provide depth in both viewing directions.
In the lab, two televisions were placed next to each other and used to view the recorded piping
operations. Using both cameras provided a three-dimensional view of the work space to
document the data collection process. Each time a new task was started, an entry was made on
the data sheet. For example, an entry might indicate that a worker was grinding a pipe. The next
entry might indicate that the worker had moved to gather the tools or materials necessary to
continue preparing the pipe for installation. The elapsed time for each task was recorded as well
as the observer’s judgment regarding whether the task was value adding (VA), non-value adding
(NVA) or non-value adding but required (NVAR).
Construction of a new chemical processing plant was observed. Several mechanical components
and interconnecting pipes were in the process of being installed. The purpose of the facility is to
supply the surrounding region with a type of chemical fire suppressant agent.
The study focused on one work area within the construction site, specifically, the final
preparation and hoisting of various prefabricated process piping components into final position.
This could only be done after all mechanical components were set into final position. Subsequent
activities included X-ray testing of each weld and a pressurized line test to determine any leakage.
The material lay-down yard was located 50 to 75 yards away from the final erection area located
on the north side of the facility.
252
2.0 Prefabricated Spool Erection Process
Few repetitive tasks occurred during the prefabricated spool erection process. A repetitive task
was defined as one in which the worker repeated the same movement or action for every
“member” (one pipe spool, valve and elbow) that was erected. For the following sections, an
activity cycle is defined as starting when work began in the area of the spool erection, and
finishing when the pipe was welded or bolted into its final place in the pipeline.
The following sections describe the erection cycles of a four-inch diameter spool approximately
eight feet long, and an eight-inch diameter spool approximately 20 feet long with an elbow in the
center of the spool. Data are also included from work attributed to a two-inch diameter spool and
a 10-inch diameter elbow section. Neither of these spools, however, was erected into final
position before the observation period ended. Figure E.1 shows the layout of the observed work
area and includes the relative position for each piping component.
Figure E.1: Layout for Observed Work Area
2.1 Spool Section Two-Inch Diameter - Data Collection
The cycle started when the pipe fitter touched the spool section that was sitting on a pipe stand.
The spool was prepared by grinding off two inches of paint from both ends. The spool was
painted offsite by a subcontractor separate from the spool fabricator. The painting subcontractor
failed to cover the ends of the spool with tape to prevent the ends from being painted; therefore,
all spools required rework (extra processing) to remove the paint from the ends. Following the
paint removal, the pipe fitter beveled each end in preparation for the production weld. This data
collection period ended before any further work was conducted on the two-inch spool.
2.2 Spool Section Four-Inch Diameter - Data Collection
The cycle started when the four-inch diameter spool was transported from the material lay-down
yard to the work area next to the facility. The spool was positioned on two pipe stands using a
forklift. The spool had a flanged connection on one end, and the other end was to be welded.
The welded end was ground down to remove the excess paint, and then beveled in preparation for
the production weld. Along with the preparatory work on the spool itself, temporary pipe stands
253
were constructed to hold the pipe in position. The spool was then wrapped with two hoist lines
and lifted into position with a boom crane. The crane held the spool in position while the
temporary bracing was adjusted and the flanged end of the spool was bolted to one of the
mechanical components. This observation cycle ended with the release of the hoist lines from the
spool.
2.3 Spool Section Eight-Inch Diameter - Data Collection
The cycle started when two of the eight-inch diameter spool sections (approximately 10 feet each)
were transported from the material lay-down yard to the work area next to the facility. The
spools were positioned on four pipe stands using a forklift. One spool had a flanged end and a
weld end; the other spool had two weld ends. All of the weld ends required paint removal, then
each weld was ground and beveled. A pipe guide was used to align and brace the two ends while
tack welds were made. Upon completion of the tack welds, the pipe guide was removed and a
production weld was made. The remaining weld end was ground and beveled. Figure E.2 shows
the finished spool. Three hoist lines were attached to lift the entire spool section into final
position. The flanged end of the spool combination was bolted to one of the mechanical
components, while the opposite end was rigged with chain falls and temporarily braced in
position until it could be secured to the structure. This observation cycle ended when the hoist
lines were removed from the spool.
Figure E.2: Complete Spool Section
2.4 Spool Section 10-inch Diameter Elbow Section Data Collection
The following section covers observed rework. The prefabricated elbow section (shown on
Figure E.3) did not meet the field requirements. Therefore, a two-inch section of pipe was
removed from the elbow section. The observation cycle started when the worker touched the
elbow section. Before the laborer began work on the elbow section, it was first positioned on two
pipe stands. Four inches of paint were then removed around the middle of the elbow. A cut was
made to sever the elbow piece and was followed by a second cut to remove two inches from the
spool section. The data collection period ended before any further work was conducted on the
elbow section.
254
Figure E.3: Cut Elbow Section
The work process for all observed cycles required a three-man crew; however, the tasks for the
four cycles required different movements and equipment to erect and secure each spool into its
final position. One cycle required bolting of the flanged end to the mechanical member, while
another cycle required the crew to bolt and weld a connection between different spools. The crew
size also changed during the actual erection process of the spool members, with a second pipe
fitter and a crane operator joining the three-man crew. Due to their limited involvement with the
entire cycle, this data was excluded from the analysis. While the three-man crew remained
constant for all of the cycles, the time required to perform the separate tasks did not. Therefore,
in contrast to the “ideal” highly repetitive and balanced manufacturing sequence, it would be
difficult to design an erection sequence that balanced both the amount of time needed as well as
the equipment necessary to complete each task.
The following section analyzes the workers’ contributions to each cycle. Table and figures show
the work distribution values for each worker and describe the time spent on VA, NVA, and
NVAR actions within each cycle.
During the observation period, the following materials were installed:
•
Two 10-foot sections of eight-inch diameter steel pipe, with one having a flanged
connection.
•
One 10-foot section of four-inch steel pipe with one flanged connection.
•
One six-foot section of 10-inch steel pipe with a 90 degree elbow and one
flanged connection.
•
One three-foot section of two-inch steel pipe with one flanged connection.
•
One pipe fitter.
•
One welder.
•
One field laborer.
•
One boom crane.
•
One forklift.
255
2.5 Piping Installation Process
In the following subsections, each worker in the crew is referred to by a field name that is used to
track his/her actions for each identified activity. (Refer to the end of this case study to review the
data collection sheets.)
The spool installation process was similar for all components during the observation period.
Each spool installation required the following: final preparation work on the ground, rigging to
lift the spool section, greasing of the flanged connection point, bolting, final adjustment and
inspections. One spool (eight-inch diameter) required an additional step before being lifted into
final position in the pipeline. Ground welding occurred to secure two 10-foot sections of eightinch pipe together; Figure E.4 includes this process. Note that ground welding did not occur for
any other spool section during this observation period and should be excluded when looking at
the remaining spool sections. Other minor subcategory tasks occurred, but were not recorded.
Figure E.4 shows the major tasks required to complete the prefabricated pipe spool installation.
The shaded areas are used to indicate that some tasks took longer to complete than others, and
that those tasks could occur simultaneously with other tasks. The shaded regions are not intended
to show actual task durations (e.g., two days for material transport to the work area).
Prefabricated Pipe Spool Installation
Process
1
2
3
4
5
6
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Material delivered to site (material yard)
Transported to work area
Final prep work (grinding/filing flange area)
"Ground Welding" of neighboring spools
Inspection of welds
Rigging spool section for lift
Piping member is hoisted into place
Gasket is greased and fit btwn. flanged spools
Bolts are inserted and hand tightened
Adjacent spools are hoisted into place
Final adjustments (leveling/inspections) of spool
Bolts are machine tightened to Specification
Final production welds are made on joint
Test and balance of line (leaks, and valve adj.)
Note: This schedule shows process flow. It does not show actual task durations.
Note: Process is similar for all prefabricated spool components (2", 4", 8", and 10" diameter spool components).
Figure E.4. Schedule for Piping Erection Process for Two-, Four-, Eightand 10-Inch Diameter Spools
2.5.1 Spool Section - Two-inch Diameter
The pipe fitter and field laborer were the only people involved with the two-inch spool section.
The welder did not contribute time to any task involving the two-inch spool section. The field
laborer was responsible for grinding and beveling the spool section while it remained on the
ground. Table E.1 and Figure E.5 show the VA, NVA and NVAR values for the field laborer.
When working with the two-inch spool section, the field laborer contributed nearly all of his time
(93 percent) to NVA actions. This was a result of the grinding and beveling actions required for
preparation of the pipe spool.
256
Table E.1: Prefabricated Piping Data for the Field Laborer - Two-Inch Diameter
A c t iv it y C la s s if ic a t io W a s t e C la s s if ic a t io n
NVA
T im e a t A c t iv it y
W a itin g
E x tra P ro c .
T ra n s p o rt
M o tio n
% o f T im e a t A c t iv it y
0 :2 3 :1 6
0 :2 4 :1 3
0 :0 6 :3 0
0 :0 1 :5 5
3 8 .8 9 %
4 0 .4 7 %
1 0 .8 6 %
3 .2 0 %
0 :5 5 :5 4
9 3 .4 3 %
0 :0 0 :3 5
0 :0 1 :1 0
0 :0 2 :1 1
0 .9 7 %
1 .9 5 %
3 .6 5 %
N V A R T o ta l
0 :0 3 :5 6
6 .5 7 %
G ra n d T o ta l
0 :5 9 :5 0
1 0 0 .0 0 %
N V A T o ta l
NVAR
M a te ria l P o s .
T .W .S .A
Field Laborer – 2 Inch Pipe Spool
NVAR Material
Positioning
1%
NVA Motion
3%
NVA Transport
11%
NVAR In-Process
Inspection
NVAR TWSA
2%
4%
NVA Waiting
39%
NVA Extra
Processing
40%
Figure E.5: Prefabricated Piping Data for the Field Laborer - Two-Inch Diameter
The pipe fitter field verified the dimensions of the two-inch diameter spool by measuring and
checking them with the latest construction documents. He was also responsible for final inspection of the beveled ends. Table E.2 and Figure E.6 show the VA, NVA and NVAR values for the
pipe fitter. Notice that the pipe fitter contributed the majority (83 percent) of his time to NVA
actions. No time was spent on VA actions.
Table E.2: Prefabricated Piping Data for the Pipe Fitter - Two-Inch Diameter
NV A
W aitin g
E xtra P ro c.
M o tio n
NV A T o ta l
0:02:47
0:03:13
0:07:47
16.78%
19.40%
46.93%
0 :1 3 :4 7
8 3 .1 2 %
NV AR
0:02:48
16.88%
NV AR T o ta l
In -P ro cess In s.
0 :0 2 :4 8
1 6 .8 8 %
G ra n d T o ta l
0 :1 6 :3 5
1 0 0 .0 0 %
257
Pipe Fitter – 2 Inch Spool Section
NVAR In-Process
Inspection
17%
NVA Waiting
17%
NVA Extra
Processing
19%
NVA Motion
47%
Figure E.6: Prefabricated Piping Data for the Pipe Fitter - Two-Inch Diameter
2.5.2 Spool Section - Four-Inch Diameter
The pipe fitter was the only crew member involved with the four-inch diameter spool section.
His main responsibilities included field verification of the dimensions of the four-inch spool by
measuring and checking them with the most up-to-date construction documents, preparing the
spool section with a hoist line, constructing temporary stands for the four-inch spool to rest on
until the adjacent spool section could be erected into place, and completing all final leveling and
adjustments while a second pipe fitter secured the flanged end to the mechanical component.
Table E.3 and Figure E.7 show the VA, NVA and NVAR values for the pipe fitter. Notice that
no actions were contributed to VA time during this erection sequence and all time attributed to
the four-inch spool section was evenly split between NVA and NVAR actions. A second pipe
fitter was introduced for a brief period to secure the flanged end to the mechanical component,
which removed any possible VA actions from the original pipe fitters.
Table E.3: Prefabricated Piping Data for the Pipe Fitter - Four-Inch Diameter
NVA
W aste Classification
W aiting
Extra Proc.
T ransport
M otion
T ime at Activity
% of T ime at Activity
0:18:12
0:08:48
0:08:10
0:06:19
22.80%
11.02%
10.23%
7.91%
0:41:29
51.96%
0:07:03
0:25:37
0:05:41
8.83%
32.09%
7.12%
NVAR Total
0:38:21
48.04%
G rand Total
1:19:50
100.00%
NVA T otal
NVAR
M aterial Pos.
In-Process Ins.
T .W .S.A
258
NVAR TWSA
7%
NVA Waiting
23%
NVAR In-Process
Inspection
32%
NVA Extra
Processing
11%
NVAR Material
Positioning
9%
NVA Transport
10%
NVA Motion
8%
Figure E.7: Prefabricated Piping Data for the Pipe Fitter - Four-Inch Diameter
2.5.3 Spool Section - Eight-Inch Diameter
All three members of the crew were involved with the eight-inch diameter spool section. The
overall tasks required to erect the eight-inch spool section were similar to those for the two- and
four-inch sections. With the eight-inch section, the added step of welding together the 10-foot
sections of pipe on the ground was included in the overall process.
The field laborer was responsible for the following: grinding off the excess paint, beveling each
end that needed to be welded, aligning the ends of each 10-foot section of pipe using a pipe guide,
and continually inspecting the work on the spool section as it progressed. Table E.4 and
Figure E.8 show the VA, NVA and NVAR values for the field laborer. More than 80 percent of
his time was spent on NVA actions, and waiting consumed the largest amount of time of all the
waste categories (52 percent).
Table E.4: Prefabricated Piping Data for the Field Laborer - Eight-Inch Diameter
NVA
W aitin g
E xtra P ro c.
T ran sp o rt
M o tio n
0:57:06
0:23:26
0:05:43
0:02:09
51.75%
21.24%
5.18%
1.95%
1 :2 8 :2 4
8 0 .1 2 %
0:02:30
0:01:26
0:18:00
2.27%
1.30%
16.31%
N V AR T o ta l
0 :2 1 :5 6
1 9 .8 8 %
G ra n d T o ta l
1 :5 0 :2 0
1 0 0 .0 0 %
N V A T o ta l
N V AR
M aterial P o s.
In -P ro cess In s.
T .W .S .A
259
Field Laborer – 8 Inch Pipe Spool
NVAR In-Process
Inspection
1%
NVAR Material
Positioning
2%
NVAR TWSA
16%
NVA Motion
2%
NVA Waiting
53%
NVA Transport
5%
NVA Extra
Processing
21%
Figure E.8: Prefabricated Piping Data for the Field Laborer - Eight-Inch Diameter
The pipe fitter was involved with the following: positioning the two 10-foot sections onto pipe
stands within the work area, aligning the two sections together with a pipe guide, and continually
inspecting the work as grinding and welding occurred on the spool. When the weld was finished,
the pipe fitter was involved with rigging and positioning the spool while it was lifted into place.
He was also required to secure the unsupported spool end with temporary bracing until the
adjacent section could be erected. Table E.5 and Figure E.9 show the VA, NVA and NVAR
values for the pipe fitter. No VA actions occurred during the erection sequence. The time spent
on NVA and NVAR actions was evenly split, with NVA and NVAR actions consuming 56 and
44 percent, respectively, of the time.
Table E.5: Prefabricated Piping Data for the Pipe Fitter - Eight-Inch Diameter
A c t iv it y C la s s if ic a t io n
NVA
W a s t e C la s s if ic a t io n
W a itin g
E x tra P ro c .
T ra n s p o rt
M o tio n
0 :3 4 :5 4
0 :1 7 :5 1
0 :1 0 :5 2
0 :4 0 :4 7
1 8 .6 1 %
9 .5 2 %
5 .7 9 %
2 1 .7 4 %
1 :4 4 :2 4
5 5 .6 6 %
0 :2 2 :3 2
0 :3 4 :1 4
0 :2 6 :2 5
1 2 .0 1 %
1 8 .2 5 %
1 4 .0 8 %
N V A R T o ta l
1 :2 3 :1 1
4 4 .3 4 %
G ra n d T o ta l
3 :0 7 :3 5
1 0 0 .0 0 %
N V A T o ta l
NVAR
T .W .S .A
260
NVAR TWSA
14%
NVA Waiting
19%
NVA Extra
Processing
10%
NVAR In Process
Inspection
18%
NVA Transport
6%
NVAR Material
Positioning
12%
NVA Motion
21%
Figure E.9: Prefabricated Piping Data for the Pipe Fitter - Eight-Inch Diameter
The welder was responsible for the following: positioning the 10-foot sections of pipe onto the
temporary stands, beveling the ends of each 10-foot section to be welded together, aligning the
two ends together using a pipe guide, tack welding, performing final production weld, continuously inspecting the production weld, rigging the finished spool section for the crane, positioning
and securing the eight-inch spool into its final position, and releasing the crane rigging from the
spool section once secured. Table E.6 and Figure E.10 show the VA, NVA and NVAR values for
the welder. Twenty-five percent of the welder’s actions were attributed to the VA category. This
value was the largest for the observed three-man crew because of welder involvement with
beveling the end sections and the final production weld. NVA actions consumed the majority of
his time at 64 percent, with the subcategory of waiting being the primary activity. Extra
processing (rework) also consumed a significant portion of time in this cycle.
Table E.6: Prefabricated Piping Data for the Welder - Eight-Inch Diameter
A c t iv it y C la s s if ic a t io n
VA
W a s t e C la s s if ic a t io n
V a lu e A d d in g
V A T o ta l
1 :2 4 :1 1
2 4 .5 8 %
1 :2 4 :1 1
2 4 .5 8 %
NVA
W a itin g
1 :4 2 :3 7
2 9 .9 6 %
E x tra P ro c .
T ra n s p o rt
M o tio n
0 :3 6 :2 8
0 :2 5 :2 3
0 :5 5 :2 1
1 0 .6 5 %
7 .4 1 %
1 6 .1 6 %
3 :3 9 :4 9
6 4 .1 8 %
0 :0 5 :3 3
0 :1 6 :1 7
1 .6 2 %
4 .7 5 %
N V A T o ta l
NVAR
0 :1 6 :4 0
4 .8 7 %
N V A R T o ta l
T .W .S .A
0 :3 8 :3 0
1 1 .2 4 %
G ra n d T o ta l
5 :4 2 :3 0
1 0 0 .0 0 %
261
Welder – 8 Inch Spool Section
NVAR In-Process
NVAR TWSA
Inspection
5%
5%
NVAR Material
VA
Positioning
25%
2%
NVA Motion
16%
NVA Transport
7%
NVA Extra
Processing
11%
NVA Waiting
29%
Figure E.10: Prefabricated Piping Data for the Welder - Eight-Inch Diameter
2.5.4 Spool Section - 10-Inch Diameter Elbow Section
The field laborer and pipe fitter were the only members of the three-man crew to work on the
10-inch elbow section. The spool section was already in the work area prior to the recording of
this data. The elbow section needed to be cut due to field variations from the construction
documents.
The field laborer was responsible for the following: positioning the elbow section on the pipe
stands, cutting the elbow section in half, cutting the elbow section down to the desired length and
grinding/beveling the cut ends of the two separated pieces in preparation for further welding.
Table E.7 and Figure E.11 show the VA, NVA and NVAR values for the field laborer. No VA
action occurred during this cycle. Nearly the entire time (96 percent) was spent on NVA actions,
with approximately 28 percent of the time spent on extra processing actions and 32 percent of the
time spent waiting for the pipe fitter.
Table E.7: Prefabricated Piping Data for the Field Laborer - 10-Inch Diameter
NVA
W a s te C la s sific a tio n
W a itin g
E x tra P ro c .
T ra n s p o rt
M o tio n
0 :5 5 :5 6
0 :4 7 :3 6
0 :2 0 :2 9
0 :4 0 :5 3
3 2 .4 6 %
2 7 .6 2 %
1 1 .8 9 %
2 3 .7 2 %
2 :4 4 :5 4
9 5 .6 9 %
0 :0 1 :0 0
0 :0 0 :1 5
0 :0 6 :1 1
0 .5 8 %
0 .1 5 %
3 .5 9 %
N V AR T o ta l
0 :0 7 :2 6
4 .3 1 %
G ra n d T o ta l
2 :5 2 :2 0
1 0 0 .0 0 %
N V A T o ta l
N V AR
T .W .S .A
262
Fie ld Labore r - 8" Pipe Spool
NVAR In-Process
Ins.
NVAR T.W.S.A
1%
16%
NVAR Material
Pos.
2%
NVA Motion
2%
NVA Waiting
53%
NVA Transport
5%
NVA Extra Proc.
21%
Figure E.11: Prefabricated Piping Data for the Field Laborer - 10-Inch Diameter
The pipe fitter was responsible for the following: field verifying the correct length for the elbow
section, preparing the pipe to be cut and continually inspecting the work as it progressed.
Table E.8 and Figure E.12 show the VA, NVA and NVAR values for the pipe fitter.
Table E.8: Prefabricated Piping Data for the Pipe Fitter - 10-Inch Diameter
NVA
W a itin g
E x tra P ro c .
T ra n s p o rt
M o tio n
N V A T o ta l
0 :2 0 :5 2
0 :3 1 :4 2
0 :0 2 :1 0
0 :0 3 :0 6
3 5 .6 7 %
5 4 .1 9 %
3 .7 0 %
5 .3 0 %
0 :5 7 :5 0
9 8 .8 6 %
NV AR
0 :0 0 :4 0
1 .1 4 %
N V A R T o ta l
T .W .S .A
0 :0 0 :4 0
1 .1 4 %
G ra n d T o ta l
0 :5 8 :3 0
1 0 0 .0 0 %
Fie ld Labore r - 10" Elbow Se ction
NVA Motion
5%
NVAR T.W.S.A
1%
NVA Transport
4%
NVA Waiting
36%
NVA Extra Proc.
54%
Figure E.12: Prefabricated Piping Data for the Pipe Fitter - 10-Inch Diameter
263
3.0 Results for the Crew
A work distribution chart (Figure E.13) depicts the time spent on various actions for the prefabricated pipe with flange and the field fabrication production processes. During the observation
period, the erection of two spools was completed. Ground work associated with preparing the
two-inch and 10-inch spools was also observed, but not the actual installation of these components. This resulted in two incomplete cycles. Figure E.13 provides an accurate representation
of the cycles observed for the four-inch diameter and eight-inch diameter spools. Both piping
components varied in size and shape and required different equipment and erection procedures.
Similar cycles did not occur during the observation; therefore, a cycle was defined as the entire
observation period. For example, the cycle started with the positioning of the eight-inch spool
onto pipe stands within the temporary workstation and concluded with the bolting and securing of
the eight-inch diameter spool into final position. The mini cycles involving the two-, four- and
10-inch spools all occurred within the total eight-inch cycle time. The different shading on the
chart represents the VA and waste tasks for each worker.
3.1 Crew Composition
The crew member controlling the flow of work around the workstation was the pipe fitter. He
dictated the actions of the field laborer and welder on each of the spool components. In an ideal
situation, the pipe fitter would form the bottleneck in the work flow. During this observation
period, however, the welder held back crew productivity. Several instances occurred in which the
production weld did not meet project specifications, requiring the weld to be removed and redone.
Notice that the time attributed to each “work classification category” varied significantly between
crew members. The largest proportion of VA actions was contributed by the welder. While the
pipe fitter contributed no VA actions to the entire process, it was his continual “in-process
inspections” which ensured that defects were not pushed on to future crews. The largest amount
of waiting occurred with the field laborer. Finally, the pipe fitter contributed the most time to
material positioning.
3.2 General Observations About Crew Composition
During the observation period, rework was a significant contributor to the high NVA value for the
entire crew. This value may have been larger than normal due to the welder’s inexperience.
Several instances occurred in which the production weld for the eight-inch diameter spool had to
be ground out and redone to meet the weld requirements. Also, it was shown through the results
of the data analysis that the pipe fitter contributed a large proportion of NVA actions to the
overall work process. Several of these actions were noted as “support” activities for the rest of
the crew. The pipe fitter constantly moved between the field laborer and welder to ensure that
quality work was being completed and the correct sequence of work was occurring. Had the
other two crew members been more experienced, the value for NVA actions would have been
lower. Finally, the entirety of the field laborer’s time was spent on NVA and NVAR actions.
Had the painting subcontractor taped the ends of each spool, the field laborer would have saved
more than one hour that was spent removing the excess paint from the ends.
264
Worker Task Breakdown
6:00:00
5:24:00
Material Pos.
0:04:05
4:48:00
In-Process Ins.
0:02:51
4:12:00
T.W.S.A
0:26:22
Material Pos.
0:29:35
In-Process Ins.
1:02:39
Material Pos
0:05:33
Value Adding
1:24:11
T.W.S.A
0:32:46
3:36:00
Transport
0:21:12
Transport
0:32:42
3:00:00
In-Process Ins.
0:16:17
T.W.S.A
Value Adding
Motion
T.W.S.A
0:16:40
Transport
Extra Proc.
In-Process Ins.
Extra Proc.
1:35:15
2:24:00
Extra Proc.
1:01:34
Waiting
Material Pos.
Extra Proc.
0:36:28
1:48:00
1:12:00
Transport
0:25:23
Waiting
2:16:18
Waiting
1:16:45
Waiting
1:42:37
0:36:00
0:00:00
Motion
0:44:57
Field Laborer
Motion
0:57:59
Motion
0:55:21
Pipe Fitter
Welder
Figure E.13: Work Distribution Chart
A goal of this report was to examine and document the inefficiencies in construction operations.
In general terms, inefficiencies were classified as the following three types: inefficiency due to
waste (NVA activities), inefficiency due to unnecessary work (excessive NVAR activities) and
inefficiency due to poorly designed work processes (ineffective VA activities). The following
section identifies opportunities for process improvement by applying Ohno’s (1988) seven wastes
in production and then evaluating the production process against a more comprehensive set of
lean principles.
Table E.9 shows the percentage of time spent on VA, NVA and NVAR as a percentage of total
cumulative time available to each worker for the entire work cycle observed. Table E.10 lists the
subset of activities that occurred to accomplish the entire erection process. In particular, the
265
NVA category is further divided into time spent in waiting, extra processing, transport and
movement categories. Additionally, NVAR actions are broken down into three subcategories to
clarify how time was spent within the observed cycles.
Table E.9: Entire Activity
Prefabricated Pipe - Entire Process
VA
Waste
NVAR
Crew Member
All
Extra
Material In Proc.
Waiting
Transport Movement
Activities
Processing
Pos.
Ins.
0%
22%
18%
6%
17%
9%
18%
Field Laborer
0%
40%
28%
10%
13%
1%
1%
25%
30%
11%
7%
16%
2%
5%
Welder
Group Percentage
8%
31%
19%
8%
15%
4%
8%
17:07:30 h:m:s
TWSA
Total
VA +
NVAR
10%
8%
5%
100%
100%
100%
37%
10%
36%
7%
100%
27%
4.1.1 Waiting
Waiting accounted for roughly one-third of the total time observed during the cycle (Table E.9).
Except for the slightly lower value of the four-inch diameter spool, the waiting time for the
remaining subcategories consistently stayed near one third (Table E.10). Waiting durations for
each member of the crew fluctuated between the different subactivities, which coincided with the
problem of balancing a crew for one work activity; this sometimes resulted in other work
activities being under- or overstaffed. Table E.10 also reflects how crew member experience
affected the amount of time spent on waiting. Table E.9 shows that the pipe fitter contributed the
least amount of time to waiting. This could be attributed to the fact that he was the most skilled
worker in the crew, and that he was coordinating work activities.
Table E.9 shows that excess movement accounted for roughly 15 percent of the entire time spent
during the cycle. Table E.10 shows relatively equal amounts of time contributed to wasted
movement. The crew members walked from the workstation to the tool shed (100 yards away)
several times to retrieve new grinder pads and welding rods. (Note: When the workers carried
material back to the workstation, it was recorded as transport, not movement.)
subsequently required modification to be operable. This included any preparation work around
connection points such as cleaning out any metal slag from the spool, beveling and grinding the
end connections prior to welding, and removing paint from all end connections. Extra processing
(rework) accounted for more than 19 percent of the total time attributed to the piping process.
The field laborer contributed roughly 28 percent of his time to grinding off the paint and cutting
the elbow spool to meet the field measurements. The pipe fitter contributed roughly 18 percent of
his time to the following: rechecking plans, taking field measurements to ensure that the prefabricated spools would fit, and aligning the correct cut line on the elbow section to guide the field
laborer.
266
Table E.10: Subactivities
Pre-Fabbed Pipe: 2" Pipe Spool
Waste
NVAR
VA
Crew Member
Extra
All
Material In Proc.
Waiting
Transport Movement
Processing
Activities
Pos.
Ins.
0%
17%
19%
0%
47%
0%
17%
Field Laborer
0%
39%
40%
11%
3%
1%
2%
Welder
0%
0%
0%
0%
0%
0%
0%
0%
34%
36%
Group Percentage
9%
13%
1%
5%
Waste
NVAR
VA
Crew Member
All
Extra
Material In Proc.
Waiting
Transport Movement
Activities
Processing
Pos.
Ins.
0%
23%
11%
10%
8%
9%
32%
Field Laborer
0%
0%
0%
0%
0%
0%
0%
Welder
0%
0%
0%
0%
0%
0%
0%
Group Percentage
0%
23%
11%
10%
8%
9%
32%
VA
Waste
NVAR
Crew Member
All
Extra
Material In Proc.
Waiting
Transport Movement
Ins.
Activities
Processing
Pos.
0%
19%
10%
6%
22%
12%
18%
Field Laborer
0%
52%
21%
5%
2%
2%
1%
Welder
25%
30%
11%
7%
16%
2%
5%
Group Percentage
13%
30%
12%
7%
15%
5%
8%
Pre-Fabbed Pipe: Elbow Section
Waste
NVAR
VA
Crew Member
Material In Proc.
Extra
All
Transport Movement
Waiting
Pos.
Ins.
Processing
Activities
0%
36%
54%
4%
5%
0%
0%
Field Laborer
0%
32%
28%
12%
24%
1%
0%
0%
0%
0%
0%
0%
0%
0%
Welder
Group Percentage
0%
33%
34%
10%
19%
0%
0%
1:16:25 h:m:s
T.W.S.A
0%
4%
0%
Total %
100%
100%
0%
3%
100%
1:19:50 h:m:s
T.W.S.A
7%
0%
0%
Total %
100%
0%
0%
7%
100%
10:40:25 h:m:s
T.W.S.A
14%
16%
5%
Total %
100%
100%
100%
10%
100%
3:50:50 h:m:s
VA +
NVAR
%
17%
7%
0%
9%
VA +
NVAR
%
48%
0%
0%
48%
VA +
NVAR
%
44%
20%
36%
36%
1%
4%
0%
100%
100%
0%
VA +
NVAR
%
1%
4%
0%
3%
100%
4%
T.W.S.A
Total %
Transportation was not as large a contributor to wasted time as the other categories. However, it
did consume 8 percent (Table E.9) of the total time. Each time a worker walked back from the
tool shed carrying a new grinder pad or welding rod, time was added to the transportation
category. Transport waste also occurred when positioning the pipe on the pipe standings to
further prepare the spools.
4.2.1 Overproduction (WIP)
this study, WIP was represented by the unfinished pipeline.
4.2.2 Inventory
Material deliveries consisted of two large shipments from the manufacturer. The prefabricated
steel pipe was delivered from the manufacturer to the painting subcontractor. The subcontractor
painted each spool section, then delivered the painted spools to the material lay-down yard. The
spools were then pulled from the material lay-down yard and moved to the workstation, where
267
final preparation work and production welds were completed. Finally, the spools were erected
into final position. It was recognized that waste in inventory occurs; however, it was not possible
to quantify this waste through physical observation.
4.2.3 Defects
Defects are defined as errors or deficiencies in a finished product that required additional work on
the part of the original crew or a follow-up crew. A faulty release valve or piping component
delivered onsite from the manufacturer is an example of a defect (i.e., the material has been
passed through the value stream to the next workstation). Another example of a defect is
included in the punch list process at the end of a job. When a defect in the finished product is
found at this stage, a separate follow-up crew is activated to correct the defect. Hence, the defect
is pushed on to the next workstation. Time spent on reworking the elbow section was accounted
for in the extra processing section. No waste associated with defects was observed.
The following paragraphs describe the current value stream map for this piping erection process,
beginning from the time the material was ordered and shipped from the manufacturer, through the
construction production process, and ending with the material in final position. Figure E.14 is a
simple flow diagram with each box representing a point in time when the material was touched,
either to be moved or transformed into the next stage (phase) in the construction life cycle.
Manufacturer
delivers
material to
site in two
large
shipments
Material is
delivered to
material laydown yard
Fabricated spool
is transported to
work area
Spool is
positioned in
work area onto
temporary pipe
stands
Rework occurs on
spools that do not
meet field
measurements
Spool is erected
and secured into
its final position
Final prep
work is
performed
on spool
Figure E.14: Material Flow Diagram
Information on delivery and handling of the piping components was obtained from the steel
erector. The basic flow of the prefabricated spools was as follows:
•
Pipe was cut, shaped and welded to specification at the manufacturer’s plant.
•
Pipe manufacturer delivered spools to cleaning and painting facility in two large
shipments.
•
Cleaning and painting subcontractor prepared spools for the site.
•
Cleaned and painted spools were delivered in two large shipments to the laydown yard.
•
Spools were pulled from the lay-down yard as needed by the field foreman (pipe
fitter) and positioned on temporary pipe stands for final preparation work within
the workstation.
268
•
If the spool did not meet the field measurements, rework (cutting spool to desired
shape) occurred on the spool until a perfect fit could be made.
•
Crane rigging was attached to the spool sections and the spool was hoisted into
its final position within the pipeline as follows:
−
Flanged ends were bolted.
−
Pipe alignment and leveling occurred.
−
Production welds were completed on nonflanged ends.
•
Temporary bracing and supports were put in place until permanent supports
could be installed.
•
Crane rigging was released.
5.1 Value Stream Map for Case Study No. 5
For the value stream map depicted on Figure E.15, three levels were needed to represent both the
material and labor components. Level One represents the major staging positions that material
must go through to reach its finished state. Each time material was moved or transformed, a stage
box is used to represent the process. Some of the stages include substages (Level Two) to
The value stream map shown on Figure E.15 was created using the information described in the
preceding section. Each major stage that the piping components went through is represented on
Level One. Two different manufacturers were used to supply piping components to the job and
are represented on this map. The material flowed from the fabricator to the painting subcontractor. An inventory position of five days between the two parties is shown. This uses an
assumption for the amount of time that the material sat before being cleaned and painted. No
substages for Level Two are represented; all values from Level Three can be directly entered into
Stage Two. No observations were made regarding Stage One since it was not directly witnessed;
however, the project superintendent confirmed that those activities occurred. An estimate of
three days total is shown for completion of Stage Two. The value stream ended once the piping
erection process reached the testing and detailing stage. Again, the limited observation period
prevented acquiring data on this stage in the entire steel erection process. Attention instead was
focused on the two substages required for Stage Two of the value stream. In Levels Two and
Three, the majority of time spent during the steel erection process was on the field fabricated
spools. In Area Three of Level Three, the total linear footage that was required to be field
fabricated or prefabricated was estimated. Using this value and the value determined for
Cumulative Time Spent per Linear Foot of Pipe, the total man-hours required to complete each
line (field or prefabricated process) could be estimated. These values are subject to change from
actual data entered into the Total Linear Feet for Each Pipe Diameter column.
269
Figure E.15: Value Stream Map
270
Table E.11 and Figure E.16 show the quick summary results for the work distribution values. Of
the 800 total workable hours committed to the piping erection process, only 58 of them were VA.
Of the total, 153 hours contributed to the NVAR category. This value was high as a result of
moving the pipe 15 feet above the floor. Finally, the overwhelming period of time spent during
the piping erection process was on NVA actions.
Table E.11: Quick Summary of Steel Process
Observation Period
Working Days
Working Time
VA Total
NVAR Total
NVA Total
35
800
58
153
590
Man-hours
Man-hours
Man-hours
Man-hours
Time Allocation of Field
for One Phase
NVA Time
NVAR Time
1
VA Time
Work Time
0
100
200
300
400
500
600
700
800
Manhours
Figure E.16: Graphical Display for the Quick Summary Table
Figure E.17 and Table E.12 illustrate how the work distribution values changed and grew
stream map were used to calculate all of the VA, NVAR and NVA values in Table E.12. As
shown on Figure E.17, the cumulative NVA line grew the fastest compared to the other work
distribution values. The black vertical line indicates when the pipe delivery process finished and
the steel erection process began. The slope change for the cumulative workable hours line
indicates that more crew members were introduced to the process. As seen on the figure, the
cumulative VA hours line finally started to grow.
271
Work Distribution
1800
1600
1400
1200
Stage 1, 2 Delivery and
material
handling
Time (man-hours)
1000
Cumulative VA Hours
800
Cumulative NVAR Hrs
Cumulative NVA Hrs
Linear (Cumulative VA Hours)
600
Stage 3 - Final
Prep and
Erection process
400
Linear (Cumulative NVA Hrs)
y = 17.384x - 20.703
200
y = 1.8922x - 6.4148
0
1
-200
3
5
7
9
Note: The values used to create
this chart are the average
11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 values from the work
entire crew.
Calendar Days
Figure E.17: Work Distribution Life Cycle Graph
272
Table E.12: Spreadsheet of Values Used to Create Work Distribution Life-Cycle Graph
Stage
Stage 1
Stage 1
Stage 2
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 2,3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 2,3
Stage 3
Stage 3
Stage 3
Stage 2,3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 2,3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 2,3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 2,3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Stage 3
Day
Monday
Tuesday
Spools are pulled from Yard and Positioned in work area
Wednesday
Thursday
Final Prep Work
Friday
Final Prep Work
Weekend
Saturday
Weekend
Sunday
Monday
Final Prep Work and Erection Process
Spools are pulled from Yard and Positioned in work area, Final Prep Work
Tuesday
Final Prep Work
Wednesday
Final Prep Work
Thursday
Friday
Weekend
Saturday
Weekend
Sunday
Monday
Final Prep Work
Tuesday
Wednesday
Final Prep Work
Thursday
Friday
Weekend
Saturday
Weekend
Sunday
Final Prep Work, Second Delivery of Spools arrives and is positioned on groun Monday
Final Prep Work, Second Delivery of Spools arrives and is positioned on groun Tuesday
Wednesday
Thursday
Final Prep Work
Friday
Weekend
Saturday
Weekend
Sunday
Final Prep Work
Monday
Tuesday
Spools are pulled from Yard and Positioned in work area, Final Prep Work Wednesday
Final Prep Work
Thursday
Friday
Final Prep Work
Weekend
Saturday
Weekend
Sunday
Monday
Tuesday
Wednesday
Final Prep Work
Final Prep Work
Thursday
Friday
Weekend
Saturday
Weekend
Sunday
Monday
Final Prep Work
Tuesday
Final Prep Work
Wednesday
Thursday
Friday
Hours
Cumulative
Cumulative
Workable Cumulative
VA
NVAR
NVA
Crew
Workable
Calendar Cumulative Calendar
worked
Workable
Calendar
available
Days
Days Calendat Days Hours
per day
days
Hours
1
1
16
16
1
1
2
8
16
16
0%
20%
80%
0
0
3.2
3.2
12.8
12.8
1
2
16
32
1
2
2
8
16
32
0%
20%
80%
0
0
3.2
6.4
12.8
25.6
1
3
16
48
1
3
2
8
16
48
0%
0%
100%
0
0
0
6.4
16
41.6
1
4
24
72
1
4
3
8
24
72
8%
19%
73%
1.92
1.92
4.56
10.96 17.52 59.12
1
5
24
96
1
5
3
8
24
96
8%
19%
73%
1.92
3.84
4.56
15.52 17.52 76.64
1
6
24
120
0
5
3
0
0
96
8%
19%
73%
0
3.84
0
15.52
0
76.64
1
7
24
144
0
5
3
0
0
96
8%
19%
73%
0
3.84
0
15.52
0
76.64
1
8
40
184
1
6
5
8
40
136
8%
19%
73%
3.2
7.04
7.6
23.12
29.2 105.84
1
9
40
224
1
7
5
8
40
176
8%
19%
73%
3.2
10.24
7.6
30.72
29.2 135.04
1
10
24
248
1
8
3
8
24
200
8%
19%
73%
1.92
12.16
4.56
35.28 17.52 152.56
1
11
24
272
1
9
3
8
24
224
8%
19%
73%
1.92
14.08
4.56
39.84 17.52 170.08
1
12
40
312
1
10
5
8
40
264
8%
19%
73%
3.2
17.28
7.6
47.44
29.2 199.28
1
13
40
352
0
10
5
0
0
264
8%
19%
73%
0
17.28
0
47.44
0
199.28
1
14
40
392
0
10
5
0
0
264
8%
19%
73%
0
17.28
0
47.44
0
199.28
1
15
40
432
1
11
5
8
40
304
8%
19%
73%
3.2
20.48
7.6
55.04
29.2 228.48
1
16
24
456
1
12
3
8
24
328
8%
19%
73%
1.92
22.4
4.56
59.6
17.52
246
1
17
24
480
1
13
3
8
24
352
8%
19%
73%
1.92
24.32
4.56
64.16 17.52 263.52
1
18
40
520
1
14
5
8
40
392
8%
19%
73%
3.2
27.52
7.6
71.76
29.2 292.72
1
19
40
560
1
15
5
8
40
432
8%
19%
73%
3.2
30.72
7.6
79.36
29.2 321.92
1
20
40
600
0
15
5
0
0
432
8%
19%
73%
0
30.72
0
79.36
0
321.92
1
21
40
640
0
15
5
0
0
432
8%
19%
73%
0
30.72
0
79.36
0
321.92
1
22
40
680
1
16
5
8
40
472
8%
19%
73%
3.2
33.92
7.6
86.96
29.2 351.12
1
23
40
720
1
17
5
8
40
512
8%
19%
73%
3.2
37.12
7.6
94.56
29.2 380.32
1
24
40
760
1
18
5
8
40
552
8%
19%
73%
3.2
40.32
7.6
102.16 29.2 409.52
1
25
40
800
1
19
5
8
40
592
8%
19%
73%
3.2
43.52
7.6
109.76 29.2 438.72
1
26
24
824
1
20
3
8
24
616
8%
19%
73%
1.92
45.44
4.56
114.32 17.52 456.24
1
27
40
864
0
20
5
0
0
616
8%
19%
73%
0
45.44
0
114.32
0
456.24
1
28
40
904
0
20
5
0
0
616
8%
19%
73%
0
45.44
0
114.32
0
456.24
1
29
24
928
1
21
3
8
24
640
8%
19%
73%
1.92
47.36
4.56
118.88 17.52 473.76
1
30
40
968
1
22
5
8
40
680
8%
19%
73%
3.2
50.56
7.6
126.48 29.2 502.96
1
31
40
1008
1
23
5
8
40
720
8%
19%
73%
3.2
53.76
7.6
134.08 29.2 532.16
1
32
24
1032
1
24
3
8
24
744
8%
19%
73%
1.92
55.68
4.56
138.64 17.52 549.68
1
33
24
1056
1
25
3
8
24
768
8%
19%
73%
1.92
57.6
4.56
143.2 17.52 567.2
1
34
40
1096
0
25
5
0
0
768
8%
19%
73%
0
57.6
0
143.2
0
567.2
1
35
40
1136
0
25
5
0
0
768
8%
19%
73%
0
57.6
0
143.2
0
567.2
1
36
40
1176
1
26
5
8
40
808
8%
19%
73%
3.2
60.8
7.6
150.8
29.2
596.4
1
37
40
1216
1
27
5
8
40
848
8%
19%
73%
3.2
64
7.6
158.4
29.2
625.6
1
38
24
1240
1
28
3
8
24
872
8%
19%
73%
1.92
65.92
4.56
162.96 17.52 643.12
1
39
24
1264
1
29
3
8
24
896
8%
19%
73%
1.92
67.84
4.56
167.52 17.52 660.64
1
40
40
1304
1
30
5
8
40
936
8%
19%
73%
3.2
71.04
7.6
175.12 29.2 689.84
1
41
40
1344
0
30
5
0
0
936
8%
19%
73%
0
71.04
0
175.12
0
689.84
1
42
40
1384
0
30
5
0
0
936
8%
19%
73%
0
71.04
0
175.12
0
689.84
1
43
40
1424
1
31
5
8
40
976
8%
19%
73%
3.2
74.24
7.6
182.72 29.2 719.04
1
44
24
1448
1
32
3
8
24
1000
8%
19%
73%
1.92
76.16
4.56
187.28 17.52 736.56
1
45
24
1472
1
33
3
8
24
1024
8%
19%
73%
1.92
78.08
4.56
191.84 17.52 754.08
1
46
40
1512
1
34
5
8
40
1064
8%
19%
73%
3.2
81.28
7.6
199.44 29.2 783.28
1
47
40
1552
1
35
5
8
40
1104
8%
19%
73%
3.2
84.48
7.6
207.04 29.2 812.48
273
Appendix F
1.0 Overview
This case study took place at a large manufacturing facility. Several large structures were being
erected in various locations onsite, and the study focused on the largest of these structures.
Unfortunately, during the observation period, several factors prevented observation of any value
adding (VA) activities. Thus, this study became a “lessons learned” case study whose purpose
was to highlight areas that, from the perspective of the observation team, were not lean.
1.1 Project Logistics
The site included roughly 1,700 acres plus an additional 300 acres reserved for future development. Several buildings would eventually occupy the site. The case study focused on piping
installation in the largest of these buildings, an approximately one million square foot structure.
Work was observed in two different locations in the building.
1.2 Work Observed
The observation period took place over two consecutive days. It focused on the installation of
Victalic piping components. Victalic pipe sections were manufactured offsite and offered the
advantage of faster installation using couplings and gaskets for each connection point rather than
requiring welding.
Approximately 30 crewmen were identified in the installation crews. These crewmen were
divided into multiple subcrews. Each crew was observed transporting piping components from
the ground to the rafters and temporarily storing the components there until trapezoidal hangers
were erected to support the pipe in final position. During the observation period, no VA actions
were evident (i.e., no hangers were erected, nor were any spools coupled). In fact, the majority of
the time during the observation period was spent on waiting and transportation waste. Rather
than exclude this case study from the report, areas are identified, at both the crew level and at
higher levels that caused the non-value adding (NVA) actions to occur.
2.0 Non-Lean Activities
This section identifies areas of non-lean conformance including complications due to the
following: material organization and delivery, nondefined work processes, conflicts resulting
from upstream processes such as incomplete slabs, and unfamiliarity with new piping material.
The material for the observed work was purchased and handled by the subcontractor. This
included all Victalic spools, couplings, gaskets and trapezoidal hangers. The larger equipment,
such as pumps, air handling units and fans, was purchased by the owner of the facility. For the
work observed, only the spools, couplings, gaskets and trapezoidal hangers were required. The
material that was onsite during the observation period was stored in two lay-down areas. The
first area was located on the north side of the facility, roughly 800 yards away from the work
area. This lay-down area served as the first staging area for material delivered from the
manufacturing facility. The second lay-down area was located in the facility. The bundles of
274
“like” spool diameters were positioned inside the facility at this point. The spools were pulled
from their respective bundles to a staging area on the ground. Different spool sizes were required
in each bay section of the building. The third staging position allowed each required spool
diameter, for each bay section, to be organized and moved at one time to the final staging position
below the rafters. From this final staging position, the spools wre lifted one at a time onto the
rafters (roof trusses). The trapezoidal hangers were not in position at this time. Each spool was
secured above its final position using cables until it could be lowered on top of the trapezoidal
hangers.
The missing hangers highlighted an area of non-lean conformance, i.e., the lack of available
materials. Several spools were temporarily positioned in the trusses even before the observation
period began. This material represented overproduction waste, which is a component of work in
progress (WIP). The cause of this particular WIP was a shortage of couplings and gaskets that
were required to connect each spool. Because these components were not ordered at the same
time as the spools, the assembly of each section was delayed.
Another area of non-lean conformance was the multiple handling of material. Roughly seven
touches were required for each spool section installed in the facility. Ideally, the piping
components would be delivered from the manufacturing facility to their final position in the
rafters. This excess material handling increased the transportation waste associated with NVA
actions.
A gas pipe spool section was observed being hoisted into the trusses and then lowered back to the
ground. Further investigation revealed that the spool was the wrong diameter for that section of
the pipeline, thus requiring it to be removed. Lean philosophy recommends incorporating “error
proof” processes whenever possible. This can be accomplished, for example, by labeling each
pipe component with a bar code, directional arrows and spool diameter. The result of lifting the
gas spool up and then down again was wasted movement, wasted transportation, extra processing
and waiting. Five crewmen were involved with the process.
There was no well-defined work process for the construction activity. At one point during the
observation period, a majority of the crewmen were working in one location. Work was then
stopped in that area of the building, and the workers were shifted to another location. This
“jumping around” was an example of the material value stream not “flowing” as it should. The
non-ideal work flow for installing spools was a result of management requiring one area of the
building to be finished one week, then shifting the focus to another area of the building the
following week before the first area was completed. The critical completion items never stayed
the same. Lean philosophy recommends starting an activity at its latest possible point. This
limits extra processing waste (another component of WIP) and also allows an activity to be
completely finished so that follow-up crews may begin their scheduled tasks.
It was observed that work at the crew level was restricted by activities occurring upstream.
Specifically, the final pour for the concrete slab occurred in the center of the building. This
prevented the pipe installation crew from erecting and installing piping components in a linear
fashion. Instead, the crews installed erected spools in one location until they reached the
incomplete section. Then they started in another location, until once again reaching the
incomplete portion. The piping foreman notified the observation team that coupling and bolting
could not begin until the slab was completed because of two 90 degree turns occurring over the
unfinished concrete slab.
275
Another non-lean area of the case study dealt with training. Several members of the crew were
not educated on the capabilities of Victalic pipe. Many crew members did not think highly of the
material because it did not require them to weld connections, as they had on previous jobs. Lean
philosophy recommends that each worker to be trained and educated in applicable work practices.
Several of the crewmen were not trained in the installation of Victalic pipe resulting in a trial and
error learning atmosphere on the job.
3.0 Concluding Remarks
The main lesson to learn from this case study is that a lack of planning and communication at the
management level affects the crews’ ability to produce VA actions. In summary, multiple work
crews were observed over a period of two days, and no VA actions were identified. For the most
part, all of the workers were reasonably busy and to a casual observer, the productivity of the
subcontractor would have appeared adequate.
276
Appendix G
Lean Questionnaire and Principle Cross-Reference
This appendix contains the final version of the questionnaire. This questionnaire forms the basis
for the Lean Assessment Tool created by the PT 191 Team. In addition to the questionnaire, this
appendix contains a table that cross-references the individual questions with the lean principle
that is being assessed.
Customer Focus
Meeting the Requirements of the
Customer
Project objectives and
1
customer requirements are not
usually discussed with all
parties involved.
2
3
4
5
6
7
N/A Project objectives and the
customer's requirements are
known by all parties involved.
1
2
3
4
5
6
7
N/A Value added is defined in terms
of the entire project by all the
participants.
3
The project is made up of
1
individuals who focus on their
own needs and own goals.
2
3
4
5
6
7
N/A Teams are formed to develop
strategies to accomplish project
goals.
4
Refocusing and reorganizing to 1
meet changing customer
requirements is a large burden
for the contractor to bear.
2
3
4
5
6
7
N/A Contractor is often able to
refocus and reorganize to
meet changing customer
requirements.
5
Project participants are often 1
inflexible due to high costs for
added changes.
2
3
4
5
6
7
N/A Project participants are flexible
in meeting situations with the
required materials, tools, labor,
etc.
2
3
4
5
6
7
N/A Crew members are able to
perform multiple tasks.
1
Define Value from the Viewpoint of
the Customer
2
Value added for the project is
defined individually by each
respective project participant.
Use Flexible Resources and
Adaptive Planning
Cross Train Crew Members to
Provide Production Flexibility
6
Crew members are encouraged 1
to stick to one specific task.
Use Target Costing and Value
Engineering
277
7
The project is built precisely
according to plans.
1
2
3
4
5
6
7
N/A The Contractor discusses ways
to modify the plans to reduce
costs while trying to maintain
quality.
Culture/People
Training
8
Employees are expected to
possess the required skills to
perform their job.
1
2
3
4
5
6
7
N/A Employees use a learning plan
to guide their development
process.
9
Contractor likes training to be 1
performed on employee's
personal time.
2
3
4
5
6
7
N/A Management encourages
development and training even
on company time.
1
10 Contractor participates in
training solely as a participant.
2
3
4
5
6
7
N/A Contractor presents training
sessions to help employees,
suppliers, and customers.
11 Employees feel that it takes a
great deal of effort to have
their supervisors hear what
they have to say.
1
2
3
4
5
6
7
N/A Employees feel that their ideas
matter to the project team.
12 Employees are focused on
completing their personal
tasks.
1
2
3
4
5
6
7
N/A Employees coordinate their
work with others to complete the
whole task.
1
2
3
4
5
6
7
N/A Top management feels the need
to change the company's culture
to improve organizational
effectiveness.
14 The company does not need to 1
work outside their own
organization to improve project
effectiveness.
2
3
4
5
6
7
N/A The company works with
suppliers, subs, and owners to
improve project effectiveness.
13 Top management is satisfied
with the status quo.
Work with Subcontractors and
Suppliers
Workplace Organization/
Standardization
Encourage Workplace
Organization and Use 5S's
278
15 Materials and tools are located 1
about the jobsite where they
were last used or where
workers think they are most
convenient.
2
3
4
5
6
7
N/A Workstations are organized with
materials and tools in their
designated places.
16 The workplace can be unkempt 1
and disorganized.
2
3
4
5
6
7
N/A The workplace follows the
principles of Sort, Straighten,
Sweep, Standardize,
Systematize.
1
2
3
4
5
6
7
N/A An in-process inspection plan is
in place to prevent rework.
18 Materials arrive on-site without 1
directional marks or any
specific assembly instructions,
and require communications
with the supplier, engineer, or
fabricator to assemble.
2
3
4
5
6
7
N/A Methods for site assembly show
piece marks or other methods to
assure a "one way only fit" such
as color coding, numbering, etc.
19 Posting information regarding 1
schedule, quality, safety,
productivity for the current job
is not of great importance.
2
3
4
5
6
7
N/A The jobsite has visual aids that
show the job status on schedule,
quality, safety, and productivity.
20 The posted information is not 1
in a place that all the workers
can see on a daily basis, and it
is not up-to-date.
2
3
4
5
6
7
N/A The posted information is in
places that most workers can see
it on a daily basis, and it is upto-date.
2
3
4
5
6
7
N/A Work processes are documented
and available to the project
team.
22 The jobsite's plan for flow of 1
materials and supplies is
conceived at the point of need.
2
3
4
5
6
7
N/A Jobsite has a logistics plan
defining access, deliveries,
movement and work
progression.
23 Workers collect materials,
tools, instructions/
specifications from locations
away from work site.
2
3
4
5
6
7
N/A Tools, materials, instructions/
specifications are collected at
the work site.
Error Proofing Devices
17 There is no inspection plan in
place to prevent rework.
Visual Management
Create Defined Work Processes
1
21 Work processes are not
documented or communicated
to the project team.
Create Logistic, Material
Movement, and Storage Plans
1
279
24 There is no posted site laydown 1
plan/drawing for storage of
equipment/materials.
2
3
4
5
6
7
N/A There is a posted site laydown
plan/drawing for storage of
equipment/materials.
2
3
4
5
6
7
2
3
4
5
6
7
N/A Work activities are planned to
minimize the movement of
people, materials, and
equipment.
N/A Material/equipment is delivered
from supplier to point of use.
1
2
3
4
5
6
7
N/A Crew sizes are usually balanced
and members are working nonstop.
28 Crew stacking or over-manning 1
is often used to maintain
schedule.
2
3
4
5
6
7
N/A Crews are usually sequenced
with regard for the schedule.
2
3
4
5
6
7
N/A Materials and information are
prepared before releasing a work
task to a crew.
2
3
4
5
6
7
N/A The crew has the ability to
switch from one task to another
to minimize downtime.
1
2
3
4
5
6
7
N/A Materials are ordered as close as
possible to exact needs.
32 Unused materials and supplies 1
are put aside and returned to
the supplier at the end of the
job or thrown out.
2
3
4
5
6
7
N/A There is a system that measures
the amount of unnecessary or
unused supplies that are ordered.
Eliminate Waste
Part I: Process Optimization
Minimize Double Handling and
Worker and Equipment Movement
1
25 Work activities are planned
without regard for movement
of people, materials, and
equipment.
26 Large material/large equipment 1
is stored in separate
laydown/storage areas or in
areas away from the jobsite.
Balance Crews, Synchronize Flows
27 Crew members may have idle
or free time on the job.
Remove Material Constraints, Use
Kitting, Reduce Input Variation
1
29 Crews are individually
responsible for gathering the
tools and information for their
work task.
Reduce Difficult
Setup/Changeovers
30 Large batches of materials are 1
produced before changing to
the next task to avoid
downtime.
Reduce Scrap
31 Extra materials are ordered to
ensure that there is always
enough.
280
Use TPM (Total Productive
Maintenance)
33 The upkeep of production
machinery and jobsite tools
occurs as needs arise.
1
2
3
4
5
6
7
N/A The upkeep of production
machinery and jobsite tools is
scheduled for workers with
down-time or off-shift time.
1
2
3
4
5
6
7
N/A Bulk materials are delivered just
prior to installation.
1
2
3
4
5
6
7
N/A Crew is given specific
instruction as to overall job
requirements.
1
2
3
4
5
6
7
N/A Work assignments are complete
in accordance with a production
schedule.
37 Work activity is started as early 1
as possible.
2
3
4
5
6
7
N/A Work is started to the latest
possible start date that still
supports the schedule.
38 Completed work products are 1
made available to the next crew
in large batches or when all
items are completed.
2
3
4
5
6
7
N/A Completed work products are
made available to the next crew
in a continuous stream or in
small batches.
39 Job is not complete before
passing on to next crew or
subcontractors.
2
3
4
5
6
7
N/A Job is completed before passing
on to next crew and
subcontractors.
Part II: Production
Scheduling
JIT Delivery
34 Bulk materials are stored onsite.
Production Planning and Detailed
Crew Instructions
35 Crew is not aware of the
overall job requirements.
Last Planner, Reliable Production
Scheduling, Short-Interval
Schedules
36 Work assignments are not
completed per original
schedule.
Pull Scheduling, The Last
Responsible Moment
Use Small Batch Sizes, Minimize
WIP
1
281
Use Decoupling Linkages,
Understand Buffer Size and
Location
1
40 Schedules, material, or
equipment buffers are
incorporated into daily practice
to accommodate unforeseen
circumstances.
2
3
4
5
6
7
N/A Material, equipment, and
resources are provided precisely
when needed.
1
41 Non-standard materials,
dimensions, and specifications
are used for ease in configuring
the design.
Use Pre-Assembly and PreFabrication
2
3
4
5
6
7
N/A Design uses readily available
materials, and emphasizes
repetitive tasks.
42 Jobs are on site labor intensive. 1
Little use of off site shops, or
jobsite pre-fabrication or
modularization.
2
3
4
5
6
7
N/A Materials are assembled in off
site shops or are pre-fabricated
on jobsite, and delivered to work
area.
1
2
3
4
5
6
7
N/A Design is made with the material
cost and the field installation
cost in mind.
44 Project designs/constructability 1
reviews are not used or needed
by the contractor before
construction starts.
2
3
4
5
6
7
N/A The contractor has verified that
the design is ready for
construction.
45 Lessons learned in the field are 1
not documented.
2
3
4
5
6
7
N/A Lessons learned in the field are
documented, and passed on to
others.
46 A written procedure is not in
place for dealing with
problems discovered in the
field.
2
3
4
5
6
7
N/A A written procedure is in place
for dealing with problems
discovered in the field.
Part III: Product
Optimization
Use Standard Parts, Reduce the
Parts Count
Use Pre-Production Engineering
and Constructability Analysis
43 Design is conceived without
consideration for the field
labor.
Continuous Improvement/BuiltIn-Quality
Prepare for Organizational
Learning and Root Cause Analysis
1
282
Develop and Use Metrics to
Measure Performance, Use Stretch
Targets
47 There is not a system in place 1
that tracks Works-In-Progress,
or where unfinished parts are
placed.
2
3
4
5
6
7
N/A Works-In-Progress are
monitored throughout the job.
48 Quality is not monitored.
1
2
3
4
5
6
7
N/A Quality is monitored.
49 Productivity is not monitored
to planned requirements.
1
2
3
4
5
6
7
N/A Productivity is monitored
against the plan and shared with
the crew.
50 When defects are discovered, 1
the project crew(s) are allowed
to shut down or pass the defect
on to another sub to fix.
2
3
4
5
6
7
N/A A plan exists that says what to
do when a defect is discovered.
1
51 A Suggestions for
Improvement program does not
exist at the jobsite level.
2
3
4
5
6
7
N/A A Suggestions for Improvement
program exists at the jobsite
level.
52 Employees feel that a defect is 1
someone else's responsibility.
2
3
4
5
6
7
N/A Employees feel the duty to
report defects.
Create a Standard Response to
Defects
Create in Employees a Sense of
Responsibility for Quality
283
Lean Principle/Questionnaire Cross-Reference
Principle
Customer Focus
Meeting the requirements of the customer
Value is defined from the point of view of the customer, not from
the point of view of individual participants
Flexible resources and adaptive planning
Cross trained crew members
Target Costs/Value Engineering
Culture/People
Training
Work with subcontractors and suppliers to regularize processes
and supply chains
Workplace Organization and Standardization
5s
Poke-yoke devices
Visual management
Defined work processes
Logistic/material movement plan
Eliminate Waste
JIT
Minimize double handling, minimize movement
Kitting, removing material constraints, reducing input variations
Balance crews, synchronized flows
Production planning, detailed crew instructions
Last planner/reliable production scheduling/short interval
production scheduling
Last responsible moment/pull scheduling
Predictable task times
Minimize WIP, Small batch sizes
Reduce parts count, Use standardized parts.
Production optimized by pre-assembly/pre-fabrication
Pre-production engineering/constructability
Reduce difficult set up/changeovers
Decoupling linkages, buffer size/location
Reduce Scrap
Continuous Improvement/Built-in Quality
Organizational learning/root cause analysis, Suggestion program
Metrics for Material, Labor, Equipment, WIP, Quality, Financial,
Productivity, and Rework
Defect response plan
Employee responsibility for correcting defects
284
Question Number(s)
1
2
3, 4, 5
6
7
8, 9, 10
11, 12
13
14
15, 16
17, 18
19, 20
21
22, 23, 24
34
25, 26
29
27, 28
35
36
37
27, 28
38, 39
41
42
43, 44
30
40
31, 32
33
45, 46
47, 48, 49
50
51, 52
Appendix H
Interview Notes
This appendix contains a summary of the interview notes that were created during and after the
site visit for each case study project. The interviews used the lean questionnaire as a guide to
discover lean practices used on the project. Also, this appendix contains the interview notes from
our meetings with lean construction early adopters. In some cases, the notes cover
projects/companies that are both case study projects and lean early adopters. In this case, the
interview notes are presented with the case study interview notes.
Case Study #1 and Early Adopter #1 – Structural Steel
Customer Focus
Optimize Value
•
They are in constant contact with the customer regarding their needs and
requirements.
•
Their practice consists of trying to “look through the customer’s eyes” to
understand how to meet their needs in a better manner.
Flexible Resources
•
They make their schedule based on the customer’s requirements, meaning they’ll
fast track it if cost is not an issue, but time is. And vice-versa if time is not an
issue, but cost is the underlying element.
•
Resources are moved or the schedule of erection is changed if the customer needs
to use a certain area, or wants a certain part completed.
Culture/People
Training
•
No lean behaviors.
People Involvement
•
They try to involve as many people as possible in the schedule.
•
Daily startup sessions/meetings are held everyday at the jobsite and at the
corporate office (kaizen).
Organizational Commitment
•
Personal performance evaluations are conducted at the end of every project.
285
•
Each engineer (structural, material coordinator, technicians) needs to come up
with at least one cost-saving idea for every project they work on. The goal of
this is to force people to “think outside the box.”
Workplace Organization
•
All laydown areas are pre-planned prior to construction beginning.
•
They try to promote the idea of “put it away if not using it.”
Visual Management
•
Safety signs are posted all over the site.
•
Productivity charts are posted in the trailer.
•
Schedule is posted in the trailer.
•
They post a flow chart for access/egress for suppliers to gain access to the site.
Eliminate Waste
Optimize Work Content
•
No lean behavior.
Optimize Production System
•
Crew size is optimized to remove inefficient or unnecessary workers.
Supply Chain Management
•
Try to implement JIT as much as possible, but have difficulty due to normal
outside barriers that come about in the construction industry.
Optimize Production Scheduling
•
On a daily basis, they look at the schedule and evaluate if the resources are
adequate or being used efficiently.
•
They use a post-job audit to evaluate how they performed on the last project, and
then they classify it as a job specific issue or something that can go into a
Lessons Learned type file.
286
Metrics
•
They measure productivity off of their schedule.
•
They measure how they performed versus cost.
Error Proofing
−
There are one-way only markings on the steel.
−
They provide tension control bolts so that the ironworkers always apply
the correct torque to the bolts.
Response to Defects
•
No real lean behavior.
Case Study #2 – Structural Steel
Data Unavailable
Case Study #3 and Early Adopter #1 – Structural Steel
Customer Focus
Optimize Value
•
They conduct formal design review sessions with the owner during the preconstruction phase of the job.
•
These design reviews are combined with milestone identifications and
explanations of milestones for the owner.
Flexible Resources
•
No specific lean practices.
Culture/People
Training
•
Training is done on company time. It includes training on lean behavior, and
driving out waste from current practices. They also train their employees to
focus on continuous improvement.
People Involvement
•
This company created a tool or system called LDMS, which stands for Lean
Daily Management System. This is a vehicle that allows all the participants
(subs, crews, Project Management, owner) to bring their ideas to the job.
287
•
This company has a system called Supply Chain Integration, which they
bring/show to their suppliers and explain their processes to the supplier.
•
They have a posted site laydown in their trailer.
Visual Management
•
Productivity reports are distributed to General Foreman and posted in the trailer.
•
Signs are posted in work area concerning safety (hardhats, safety glasses).
•
These are included in their visual management.
Eliminate Waste
•
They prefab as much as possible. The Designer, in their case the structural
engineer meets with the field labor to discuss Constructability. This is a new
phenomenon used since the engineer visited a couple of sites previously and
realized this was a necessary function.
•
No specific lean practices or behaviors.
•
No specific lean behaviors.
•
They make an effort to pass things on in small batches or continuous streams.
This is not always met, but the effort is there.
•
Have a lessons learned file, but not used often due to dissimilar projects.
•
Written procedures are placed in the lessons learned file.
288
•
There is a Suggestions for Improvement box.
•
They monitor quality and productivity.
Metrics
Error Proofing
•
They make sure their steel is delivered with a “one-way only fit.”
Response to Defects
•
They have written plans of what to do when a defect occurs. Forms must be
submitted when there is a defect, and these are also placed in their lessons
learned file.
Case Study #4 – Piping
Customer Focus
Optimize Value
•
They advocate their General Foremen and Foremen to meet with the Owner’s
operators to understand their specific needs for the site.
•
They are flexible with the Owner’s request to meet them on site to discuss any
needs or requirements by the Owner.
Flexible Resources
•
They are flexible with their labor workforce since their location is near the
largest local pipe fitter union in the country.
Culture/People
Training
•
Training under a person that has already done one’s job is required in the project
management level, meaning there is a specific ladder to climb to finally be able
to run a job.
People Involvement
•
This company creates milestones for its workers to strive for, in the purpose of
promoting employee empowerment.
•
The company is committed to improvement by using employee teams to further
research and find more cost effective ways to construct and do business.
289
•
They have a standard tool trailer with labeled bins for all the tools.
•
They place their laydown area where the owner designates.
Visual Management
•
Productivity reports are distributed to General Foreman and posted in the trailer.
•
Signs are posted in work area concerning safety (hardhats, safety glasses).
•
They use a material coordinator to help with the flow of their jobsite.
Eliminate Waste
•
No lean behaviors.
•
They go to great detail to plan activities that will result in the least amount of
movement.
•
No lean behaviors.
•
No lean behaviors.
•
Have a lessons learned file, but not used often due to dissimilar projects.
•
They monitor quality as often as they can.
Metrics
Error Proofing
•
Use chalk/markers to label ends of pipes.
Response to Defects
290
•
They have a Quality Assurance person flag the ISO, a decision will be made if
work can continue or if repairs need to be done before moving on.
Data not available.
Customer Focus
Optimize Value
•
Flexible Resources
•
Culture/People
Training
•
Routine training occurs. They focus on crisis management in training sessions.
That is not a lean behavior; it is a reactionary behavior as opposed to proactive
behavior, which would be lean.
People Involvement
•
They encourage feedback from the field labor.
•
The company is not satisfied with current practices, and looking to improve.
That is necessary in lean thinking (continually eliminate the waste).
•
Visual Management
•
Visual tools are solely in the trailer.
•
They have a formal contract work process. ISO 9000 related. This work process
is in electronic form.
291
•
They conduct weekly meetings to discuss access, logistics.
Eliminate Waste
•
•
•
They are practicing JIT, but it is due to conditions and not planning. They are
doing JIT by default on this job.
•
This is not always met, but the effort is there.
•
They have a Value Awareness Report. Lessons Learned are included in this file.
•
QA/QC is monitored daily in accordance to the specifications.
Metrics
Error Proofing
•
Response to Defects
•
Early Adopter #2 – General Contractor – Commercial Buildings
Customer Focus
Optimize Value
•
They use target costing to communicate with the customer.
•
Value Engineering is implemented to give the customer function analysis. This
shows them pricing and costs if they want certain things.
292
Flexible Resources
•
No specific lean practices.
Culture/People
Training
•
There is a “Boldt University” that mandates courses on three different levels of
lean training. Over 200 Boldt employees have been trained on lean theory, and
how to use their Last Planner model.
People Involvement
•
The Last Planner system that Boldt emphasizes inherently creates employee
empowerment. It forces each participant to explain the work they are doing,
when it will be completed, and also allows them to make suggestions.
•
Crews have daily meetings as well to keep them involved.
•
Every year 7-8 strategic goals are stated by the company. At least one of these
goals is focused on innovation and using Lean Construction Initiatives to
improve processes.
•
No specific lean behaviors. Looking to implement the 5 S’s next year.
Visual Management
•
Production information is distributed to all participants at each weekly Last
Planner meeting. This information includes the detailed plan for the next week
along with plan reliability measurements from the previous week and the whole
job. This allows everyone to see status on schedule and productivity.
•
Eliminate Waste
•
They use the combination of CPM and Last Planner to balance their work flow
and crew flow.
•
They track manpower hours to figure out optimal sequencing.
293
•
•
No specific lean practices or behaviors. Want to implement more JIT principles
in the near future.
•
Again using the Last Planner system to hand-off products in small batches or in a
continuous stream. They have focused real hard in the last 4 years on the handoff principle. Their goal is to better manage the actual hand-off of work between
activities as opposed to managing the activity itself.
•
Boldt implemented an OFI program 12 years ago. Opportunities For Improvement are suggestions employees make to improve processes. Last year 250-300
OFIs were documented. The employees earn “Boldt bucks” for submitting an
OFI and even more Boldt bucks if the ideas are implemented.
•
They also have a Lessons Learned File that can be accessed through their
intranet.
•
They measure productivity.
•
They are intent on having quality measurements decentralized all the way down
to the lowest level of the organization. This is the theory that each worker should
check his/her own work and make sure it is of good quality before passing it on.
Metrics
Error Proofing
•
Response to Defects
•
294
Early Adopter #3 – Mechanical Design/Build
Customer Focus
Optimize Value
•
Have implemented Design-Build and Design-Assist Delivery systems where they
have a full understanding of customer’s needs from the inception of the project.
•
Make employees fill out a Planning Checklist for each project where questions
are asked to see if the employees know the client’s goals and what business the
clients are in.
Flexible Resources
•
Makes sure project teams have clear lines of communication to help if changes
need to be made on the project, especially if made by the client.
Culture/People
Training
•
The company has its own Internet system that is used as a tool in many regards.
There are numerous training sessions on the system.
•
Foremen are trained once a month as well as whenever there is something they
need to be trained in.
People Involvement
•
Employees are rewarded as a team when a project goes well, and not by
individual trades. This forces them to think as a team.
•
Cross-functional teams are formed to keep coordination between trades.
•
Organization is very committed to continual improvement. Empowerment of
employees is driven from the top down with encouragement from above to find
more effective processes.
•
Company asks suppliers to find more effective practices, which is complied with
since same suppliers are on 95 percent of their projects.
•
Boxes are created for each crewman with everything they would need for that
day.
295
Visual Management
•
There is a visual for the material handling process.
•
There is a visual of the productivity analysis.
•
Safety is measured and reported every month.
•
All of their work processes are in some form of visual aid.
•
There internal system prints out visual reports that define all work processes.
•
They have checklists that each employee must follow which include what their
task is, how it should be done, what tools and materials are needed, and the
possible safety hazards and how to prevent them.
Eliminate Waste
•
Effort is put in the design phase to standardize their materials, joints.
•
Lessons Learned file is used to see how to optimize current project.
•
Checklist is used to see how current project is similar to a previous project.
•
•
•
Lessons Learned files are made at the close-out of every project.
•
They have OFIs (Opportunities For Improvement) that they encourage
employees to fill out.
•
Meetings are held to talk about innovative ideas to improve processes for the
future.
296
Metrics
•
•
They measure the amount of unused supplies and materials for each job. This is
done with the help of one of their suppliers. Suppliers are in accordance with this
program since they are usually the same for each job.
Error Proofing
•
They color-code their fire sleeves to clarify between supply lines and return lines.
Response to Defects
•
Field empowerment is encouraged to raise the flag and deal with the defect at
hand.
Early Adopter #4 – General Contractor Industrial Buildings
Customer Focus
Optimize Value
•
Company supplies JIT training to its A/E so they can understand lean and its
communication tools for the owner.
•
Program called VAVE (Value Added Value Engineering) is used to help
communicate the owner’s needs and goals on every level.
Flexible Resources
•
Two week look-ahead planning is used with subcontractors to combat problems
early on.
Culture/People
Training
•
Mandatory 8 hour lean training sessions for all employees.
•
Lean “best practices” mandatory for every project.
•
Average of 40 hours training/employee/year.
People Involvement
•
Use CIM (continuous improvement message) to keep employees thinking and
involved. Also use OFIs (Opportunities for Improvement) cards, which are along
the same lines as CIM.
297
•
Organization is very committed to continual improvement.
•
Training and conversations always occur with Subs regarding lean practices.
•
5s is used on all jobsites for cleanliness and organization.
Visual Management
•
Everything that is tracked is posted. One of the only companies visited that
posted numerous visual aids at the workplace.
•
Visual aids are updated weekly.
•
A jobsite logistics plan is used that defines workflow, access, etc. This is a visual
aid as well.
Eliminate Waste
•
Pre-Fabrication is used whenever possible.
•
Architects and Engineers are trained in Just-In-Time concepts. This teaches them
about the benefits of using standardized materials for repetitive tasks.
•
A four-week look ahead to plan subs movement is used.
•
They coordinate weekly sub-contractors meetings.
•
Have trained approximately 160 suppliers and sub-contractors about lean
behaviors and principles.
•
The four-week look ahead planning is used here to support smooth flow from sub
to sub.
298
•
They keep three lessons learned files. One for lean behaviors, one for activities,
and one with the CIMs.
•
Metrics
Error Proofing
•
Response to Defects
•
Employees and subs are encouraged and empowered to report defects, especially
with matters concerning safety.
299
Appendix I
Worker Movement Study No. 1
1.0 Worker Movement Analysis
1.1 Background
In the manufacturing world, where the lean idea was first developed, intercell flow has been
extensively analyzed to optimize factory layout, work space sequence and equipment selection
and to improve overall productivity. An efficient flow of workers, materials and information
among various cells or workstations is one of most important requisites for overall productivity
improvement. However, the construction industry has not readily adopted this flow analysis
concept because of the difficulties of applying the analysis to the construction process. The
following are some characteristics that hamper the construction industry from adopting movement (flow) analysis:
•
Single unique project rather than multiple products.
•
Different environment for each jobsite.
•
Dynamic workstation; locations change as work progresses.
•
Three-dimensional oriented workstation locations, which are difficult to analyze.
Despite the difficulties of conducting movement (flow) analysis in construction, the need for such
information continues. Although this analysis does not apply to all construction processes, it
serves as an experimental attempt at movement analysis of the steel erection process.
1.2 Scope and Goal
Essentially all movements - either worker or material - are considered to be non-value adding
(NVA) activities. However, some movements are non-value adding but required (NVAR).
NVAR movements are unavoidable; therefore, to promote more efficient or “leaner” construction, NVA movement has to be minimized. This study has the following three main goals:
•
To develop an appropriate scheme for the evaluation of flow efficiency.
•
To evaluate the process and measure the degree of leanness.
•
To analyze causes of NVA movements and suggest solutions.
Due to the complexity of the construction process mentioned earlier, this analysis has a few scope
limitations, which are described in the following subsections.
1.2.1 Only Worker Movements Were Analyzed
This study evaluated the movement of workers in the Noland Project steel erection process. As
mentioned earlier, there are three types of flow: workers, materials and information. Unlike
300
manufacturing, where most of the workers are stationary and material moves from one location to
another, in construction, both workers and materials move from one location to another.
Therefore, both worker and material movements are equally important. However, material
movement was excluded from this study mainly because the materials were already delivered and
positioned before the observation started. Despite the improvement of communication tools, the
information flows primarily between workers. Therefore, information flow is very much tied to
worker movement and was not considered separately in this study.
1.2.2 Type and Number of Crew; Equipment Was Not Changeable
There are several factors that contribute to NVA movements. These include inefficient layout,
work space congestion and improper crew and equipment selection. One goal of this study was
to find the cause of unnecessary movement using the perspective of site layout and the work
sequence plan. However, understanding that each project has a unique environment and there are
thousands of other associated activities, this study assumed that the crew and equipment selection
was not changeable.
1.3 Methodology
1.3.1 Worker Movement Diagram Construction
Using field observations, videotape review and the site plan, the structure being constructed and
the movement paths of four workers (forklift operator, x-bracing connector, right connector and
left connector) were sketched. The locations of various workstations and the places where
workers stopped were indicated with marks and numbers. The Actual Movement Diagram,
which contains both the NVA and NVAR movements of workers, is located at the end of this
appendix.
Using observations and a logical thinking process, NVAR movements and unavoidable stops
were identified. With minimum moving distances and stops, an Ideal Movement Diagram was
constructed, which is located at the end of this appendix.
1.3.2 Numerical Analysis
Frequent, unnecessary stops are an indicator of unproductive worker movement. When a worker
finishes or hands off a task and moves to another location, time and energy are consumed.
Therefore, the number of stops can be directly correlated to the level of productivity; fewer stops
mean less wasted movements. The number of stops was counted for both actual and ideal
movements for this analysis. For each worker, this number was then given a rating to convey
stop efficiency as follows:
Efficiency = Resources Expected to Be Spent/Resources Actually Spent.
Stop Efficiency = Number of Ideal Stops/Number of Actual Stops.
A higher efficiency rate signifies better productivity in terms of worker movements.
301
Even if one worker made the same number of stops as another, his movement may still be NVA if
he went the long way around from one point to another. Therefore, total distance traveled is an
equally important factor in the movement efficiency rating, which is computed as follows:
Distance Efficiency = Ideal Travel Distance/Actual Travel Distance.
Measuring distance can be a very complex process because of the nature of worker movement in
construction. The construction process can be very three-dimensionally oriented, which means
that activities are carried out above as well as on the ground. This makes it harder to measure the
exact distance between two locations. To overcome this difficulty and achieve more accurate
measurements, a three-dimensional coordinate system was adopted. A reference point was
selected and each workstation and stop were assigned X, Y, and Z coordinates, so that distance
measurement could become simpler.
Curved movement path was another problem in distance measurement. Most construction
activities take place in an open field where no aisle, corridor or walking path yet exists. To
overcome this difficulty, an approximated distance measurement method was used.
The curve connecting Points A and B is
arbitrary and makes it very difficult to
measure the length.
However, it is
obvious that the curve length will be
longer than the straight (Euclidian)
distance represented by the single-dotted
line and shorter than the double-dotted
line (Rectilinear). Therefore, the curved
line length was approximated by the
average of the Euclidian and Rectilinear
distances. When the end point coordinate
is known, Euclidian and Rectilinear
distances can be measured using the
following equations:
Rectilinear Distance = |XB - XA| + |YB - YA | + |ZB - ZA|
Euclidian Distance = {|XB - XA|2 + |YB -YA |2 + |ZB - ZA|2}1/2
Actual Distance ≈ (Rectilinear Distance + Euclidian Distance)/2
1.4 Analysis Results and Evaluation
1.4.1 Forklift Operator
Stop Efficiency
Actual
Stops
20
Ideal
12
302
Efficiency
0.6
Distance Efficiency
Actual
Rectilinear
892
Euclidian
735.0
Average
Ideal
695.0
578.3
Efficiency
0.78
0.79
0.78
Although the forklift operator had significant wasted movements, the efficiency was relatively
high. This resulted from on-the-ground oriented workstation locations. The two main tasks of
the forklift operator were delivering steel parts from the stock yard to the erection location and
hooking the parts onto the crane cable. Both types of work were conducted on the ground, so the
forklift operator only had two-dimensional oriented movements, which tended to have less waste
relative to three-dimensional movements.
The following is a description of some key wasted movements, corresponding causes and
possible solutions for improvement:
NVA Occurred Between
02 - 04
Cause
Task in other location
07 - 09
Inefficient routing
Solution
Complete all other tasks before
moving on to the next location
Carefully select route
1.4.2 X-Bracing Connector
Stop Efficiency
Actual
Stops
31
Distance Efficiency
Actual
Rectilinear
1557.0
Euclidian
1157.2
Average
Ideal
18
Efficiency
0.58
Ideal
312.0
241.3
Efficiency
0.20
0.21
0.20
The x-bracing connector encountered the most interference from other workers’ movements
because he worked at an internal location. Therefore, his efficiency was generally lower than the
others. There was not much significance in the stop efficiency, but the distance efficiency was
very low. The x-bracing connector got in the way of material delivery a few times, and it forced
him to pull back from his workstation and led to a significant increase in movement distance.
05 – 06
08 – 12
16 – 20
Cause
Unexpected trouble in the
girder erection
Space congestion
Space congestion
303
Solution
Pause the process until one problem
is completely solved
Preplan work sequence
Preplan work sequence
1.4.3 Right Connector
Stop Efficiency
Actual
21
Ideal
16
Efficiency
0.76
Distance Efficiency
Actual
Rectilinear
488
Euclidian
445.5
Average
Ideal
230.0
230.0
Efficiency
0.47
0.52
0.49
Stops
Although the right connector had very similar tasks as the left connector, the right connector had
better stop efficiency and worse distance efficiency. The right connector had better stop
efficiency because, by the nature of the work, he could stay on one side of the structure for both
girder and bar joist erection, while the left connector had to move to various locations. The
reason for lower distance efficiency was interference from the crane. During the erection process,
the crane was located at the right side of the structure and got in the way of the right connector’s
man-lift movement.
07 – 09
11 – 15
Cause
Manlift position adjustment
Detour around the crane
Solution
Minimize worker mistakes
Improve site layout
1.4.4 Left Connector
Stop Efficiency
Actual
27
Ideal
17
Efficiency
0.63
Distance Efficiency
Actual
Rectilinear
694
Euclidian
595.1
Average
Ideal
410.0
343.0
Efficiency
0.59
0.58
0.58
Stops
The left connector had relatively good overall efficiency. The left connector worked mostly on
top of the existing structure instead of using a man-lift, and he had little wasted movement. In
addition, the left connector had no significant NVA movement during the observation. The
efficiency rate was not particularly good mainly due to the up and down movements of the manlift when moving from one workstation to the next.
11 - 15
Cause
Gets onto the structure for
bar joist erection
304
Solution
Work from the top of the structure
which brings better overall efficiency
1.5 Further Analysis Plan
1.5.1 Comparative Case Study of Various Projects
Because of the diversity of task types, equipment and other circumstances, a simple efficiency
rate cannot properly evaluate the movement of various workers. Therefore, analysis of one single
project will not provide reliable, generalizable conclusions. To moderate this obscurity, more
case studies of similar and different project types should be conducted.
1.5.2 Improvement of Analysis Tool
As discussed earlier, measuring the exact distance of the arbitrary movements of workers is not
an easy job. Finding a proper tool, such as computer software, will improve the accuracy of
analysis. Employing a Global Positioning System (GPS), which has been significantly enhanced
in terms of accuracy and cost, can be another method to improve analysis.
305
306
307
Appendix J
Worker Movement Study No. 2
1.0 Worker Movement Analysis
1.1 Overview
This study presents an analysis of two workers (left and right connectors) during two hours of
real-time work. The tasks and installation methods of these connectors were very similar to the
left and right connectors in the Noland Project. However, unlike the Noland Project, only the
beam installation process was effectively filmed and available and only two workers were visible
most of the time in the film. Therefore, this study analyzes only these two workers as they
performed the beam installation; a diagram of their actual movements is included at the end of
this appendix.
A total of 13 beams were installed during the time of analysis. Among 13 beams, six were
shorter and seven were longer. The shorter beams were one span length, and the longer ones
three span lengths. Due to the two different beam sizes, the work order was somewhat complex;
workers had to travel longer distances than necessary and the efficiency of worker movement was
affected.
1.2 Analysis Results and Evaluation
1.2.1 Right Connector
The right connector had two major duties: to connect the delivered beam and to unhook the crane
cable from the beam. As in the first case study project, the right connector worked on top of a
man-lift. After connecting the beam, he made small movements such as walking a few steps or
bending over to unhook the beam within the lift space. Such small movements were ignored in
the analysis.
The primary movements were made between one beam installation and the next. Therefore, most
movements were made among various workstations. The order of beam installation was mainly
left to right, one row at a time. After the connector moved all the way to the right, he lowered the
man-lift to the ground and drove back to the far left to work on the next row. This travel distance
was significant and lowered efficiency. On the Ideal Movement Diagram located at the end of
this appendix, the work process was designed to work north to south in zigzag order to minimize
travel distance and number of stops. The following tables show the stop number and travel
distance efficiency of the right connector:
Stop Efficiency
Actual
17
Ideal
13
Efficiency
0.76
Distance Efficiency
Actual
Rectilinear
480
Euclidian
453.7
Average
Ideal
220.0
194.8
Efficiency
0.46
0.43
0.44
Stops
308
1.2.2 Left Connector
The left connector had the same duties as the right connector. The work time for each task was
almost identical and movements were made in a very synchronic manner. Therefore, the distance
efficiency and stop numbers of the left connector were almost the same as those of the right
connector. The small difference in distance efficiency was caused by the different man-lift
operation styles of the left and right connectors. The following are the results of the analysis:
Stop Efficiency
Actual
17
Ideal
13
Efficiency
0.76
Distance Efficiency
Actual
Rectilinear
510
Euclidian
461.8
Average
Ideal
260.0
218.6
Efficiency
0.51
0.47
0.49
Stops
1.3 Comparison between Case Study No. 1 and Case Study
No. 2
The analysis involved only two workers, the left and right connectors. However, the tasks,
equipment and work environments of connectors for both projects were very similar. Therefore,
the evaluations of the connectors’ movements can be analyzed to formulate a conclusion. The
results of both Case Study No. 1 and Case Study No. 2 for worker movement are presented in the
table below:
Right
Left
Case No. 1
Case No. 2
Stop No.
0.76
0.76
Distance
0.45
0.44
Stop No.
0.63
0.76
Distance
0.58
0.49
When compared to the others, the Case No. 1 left connector had a somewhat lower stop
efficiency and higher distance efficiency. This was due to the special circumstance of working on
top of the structure next to workstations instead of riding the man-lift. Because of this, he has
been omitted from consideration.
The resulting efficiencies of all other workers were very similar; therefore, it can be concluded
that the overall job efficiencies were comparable for both projects. However, the causes of
efficiency drop between the two projects were quite different. Many unnecessary stops were
made and travel distance was increased due to space congestion in Case Study No. 1. In Case
Study No. 2, an inefficient work order was the primary cause of the efficiency drop. To further
increase efficiency and minimize worker movement at the jobsite, optimal work orders and space
sharing arrangements should be preplanned.
309
An interesting finding in Case Study No. 1 was that space congestion was minimal. The forklift
and ground crews worked from the actual jobsite where the installation took place. This made the
swing angle and carry-over distances greater for the crane; however, it helped to minimize space
congestion on the jobsite.
310
311
312
References
Alarcon, L., 1996, “Performance Measuring Benchmarking and Modeling of Construction
Projects,” Proceedings of the Fourth Annual Conference of the International Group for Lean
Construction (IGLC-4), Birmingham, UK.
Alves, T. and C. Formosa, 2000, “Guidelines for Managing Physical Flows in Construction
Sites,” Proceedings of the Eighth Annual Conference of the International Group for Lean
Construction (IGLC-8), Brighton, UK.
Arbulu, R., I. Tommelein, et al., 2002, “Contributors to Lead Time in Construction Supply
Chains: Case of Pipe Supports Used in Power Plants,” 2002 Winter Simulation Conference, San
Diego, CA.
Ballard, G., 1999, “Improving Work Flow Reliability,” Proceedings of the Seventh Annual
Conference of the International Group for Lean Construction (IGLC-7), Berkeley, CA.
Ballard, G., 2000a, “Last Planner System of Production Control,” Thesis submitted to Faculty of
Engineering, University of Birmingham, Birmingham, 192.
Ballard, G., 2000b, “Lean Project Delivery System,” White Paper No. 8, Lean Construction
Institute.
Ballard, G., 2000c, “Managing Work Flow on Design Projects,” CIB W96, Atlanta, GA.
Ballard, G., M. Casten, et al., 1997, “PARC: A Case Study,” Proceedings of the Fourth Annual
Conference of the International Group for Lean Construction (IGLC-4), Birmingham, UK.
Ballard, G. and G. Howell, 1998, “What Kind of Production Is Construction,” Proceedings of the
Sixth Annual Conference of the International Group for Lean Construction (IGLC-6), Guarujá,
Brazil.
Ballard, G., L. Koskela, et al., 2001, “Production System Design: Work Structuring Revisited,”
White Paper, Lean Construction Institute.
Bertelsen, S. and L. Koskela, 2002, “Managing the Three Aspects of Production in Construction,”
Proceedings of the Tenth Annual Conference of the International Group for Lean Construction
(IGLC-10), Gramado, Brazil.
Ciampa, D., 1991, “The CEO’s Role in Time-Based Competition,” J. D. Blackburn, ed., In TimeBased Competition, Business One Irwin, Homewood, IL.
Cronbach, L. J., 1951, “Coefficient Alpha and the Internal Structure of Tests,” Psychometrika 16,
297-234.
Crowley, A., 1998, “Construction as a Manufacturing Process: Lessons from the Automotive
Industry,” Computers & Structures, 67, 389-400.
313
dos Santos, A., 1998, “Principle of Transparency Applied in Construction,” Proceedings of the
Sixth Annual Conference of the International Group for Lean Construction (IGLC-6), Guarujá,
Brazil.
dos Santos, A., 1999, “Application of Flow Principles in the Production Management of
Construction Sites,” School of Construction and Property Management, University of Salford.
dos Santos, A. J. Powell, et al., 2000, “Reduction of Work-In-Progress in the Construction
Environment,” Proceedings of the Eighth Annual Conference of the International Group for Lean
Duggan, K. and J. Liker, 2002, Creating Mixed Model Value Streams: Practical Lean Techniques for Building to Demand, New York, NY, Productivity Press.
Eagan, J., 1998, Rethinking Construction, London Department of the Environment, Transport and
the Regions, 40.
Fearon, H., W. Ruch, et al., 1979, Fundamentals of Production/Operations Management, New
York, NY, West Publishing Company.
Fowler, F. J., 1995, Improving Survey Questions: Design and Evaluation, Thousand Oaks, CA,
Sage Publications.
Freire, J. and L. Alarcon, 2002, “Achieving Lean Design Process: Improvement Methodology,”
Journal of Construction Engineering and Management, Volume 128, No. 3, May-June 2002,
248-256.
Fujimoto, T., 1999, The Evolution of a Manufacturing System at Toyota, New York, NY, Oxford
University Press.
Galbraith, J., 1974, “Organization Design: An Information Processing View,” Interfaces, 4, 2836.
Hatcher, L., 1994, “A Step-by-Step Approach to Using the SAS(R) System for Factor Analysis
and Structural Equation Modeling,” Cary, North Carolina, SAS Institute.
Hopp, W. and M. Spearman, 1996, Factory Physics: Foundations of Manufacturing Management, Boston, MA, Irwin/McGraw-Hill.
Howell, Greg and Glenn Ballard, “Implementing Lean Construction: Understanding and Action,”
Proceedings of the Sixth Annual Conference of the International Group for Lean Construction
(IGLC-6), Guarujá, Brazil.
Koskela, L., 1992, “Application of the New Production Philosophy to Construction,” Technical
Report 72, CIFE, Stanford University, 75.
Koskela, L., 2000, An Exploration into a Production Theory and Its Application to Construction,
Helsinki University of Technology, Espoo, Finland, VTT Publications, 298.
314
Koskela, L., G. Ballard, et al., 1996, “Towards Lean Design Management,” Proceedings of the
Fourth Annual Conference of the International Group for Lean Construction (IGLC-4),
Birmingham, UK.
Lane, R. and G. Woodman, 2000, “Wicked Problems, Righteous Solutions, Back to the Future on
Large Complex Projects,” Proceedings of the Eighth Annual Conference of the International
Group for Lean Construction (IGLC-8), Brighton, UK.
Lantelme, E. and C. Formoso, 2000, “Improving Performance Through Measurement: The
Application of Lean Production and Organizational Learning Principles,” Proceedings of the
Eighth Annual Conference of the International Group for Lean Construction (IGLC-8), Brighton,
UK.
Lareau, W., 2000, Lean Leadership: From Chaos to Carrots to Commitment, Tower II Press,
Carmel, Indiana.
London, K. and R. Kenley, 2001, “An Industrial Organization Economic Supply Chain Approach
for the Construction Industry: A Review,” Construction Management and Economics, 19, 777788.
MacInnes, R., 2002, The Lean Enterprise Memory Jogger, Salem, NH, Goal/QPC.
Matthews, O., G. Howell, et al., 2003, “Aligning the Lean Organization: A Contractual
Approach,” Proceedings of the Eleventh Annual Conference of the International Group for Lean
Construction (IGLC-11), Blacksburg, VA.
McClelland, G., 2003, Personal Communication, Department of Psychology, University of
Colorado.
Nisbett, R., 2003, The Geography of Thought: How Asians and Westerners Think Differently and
Why, New York, NY, The Free Press.
Nunnaly, J., 1978, Psychometric Theory, New York, NY, McGraw-Hill.
Ohno, T., 1988, Toyota Production System, New York, NY, Productivity Press.
Oppenheim, A. N., 1992, Questionnaire Design and Attitude Measurement, London, Pinter
Publishing, Ltd.
Pappas, M., 1999, “Evaluating Innovative Construction Management Methods through the
Assessment of Intermediate Impacts,” Civil Engineering, Austin, TX, University of Texas at
Austin.
Picchi, F., 2001, “System View of Lean Construction Application Opportunities,” Proceedings of
the Ninth Annual Conference of the International Group for Lean Construction (IGLC-9),
Singapore.
Plossl, G., 1991, Managing in the New World of Manufacturing, Englewood Cliffs, NJ, PrenticeHall.
315
Rea, L. and R. Parker, 1997, Designing and Conducting Survey Research: A Comprehensive
Guide, San Francisco, CA, Jossey-Bass.
Rother, M. and J. Shook, 1998, “Learning to See: Value Stream Mapping to Create Value and
Eliminate Muda,” Brookline, MA, The Lean Enterprise Institute.
Schonberger, R. J., 1996, World Class Manufacturing: The Next Decade, New York, NY, The
Free Press.
Schroeder, R., 1993, Operations Management: Decision Making in the Operations Function,
Columbus, OH, McGraw-Hill International Editions.
Serpell, A., 1966, Proceedings of the Fourth Annual Conference of the International Group for
Lean Construction (IGLC-4), Birmingham, UK.
Seymour, D., 1996, “Developing Theory in Lean Construction,” University of Birmingham, 24.
Shingo, S., 1981, Study of the Toyota Production System, Japan Management Association, New
York, NY, Productivity Press.
Stalk, G. J. and T. Hout, 1990. Competing Against Time, New York, NY, Free Press.
Tapping, D., T. Luyster, et al., 2002, Value Stream Management, New York, NY, Productivity
Press.
Tommelein, I., 1998, “Pull-Driven Scheduling of Pipe-Spool Installation: Simulation of Lean
Construction Technique,” ASCE Journal of Construction Engineering and Management,
Vol. 124, No. 4 (July/August), 279-288.
Tommelein, I., N. Akel, et al., 2003, Capital Projects Supply Chain Management: SC Tactics of
a Supplier Organization, Construction Research Congress, Honolulu, HI, ASCE.
Tommelein, I. and A. Li, 1999, “Just in Time Concrete Delivery: Mapping Alternatives for
Vertical Supply Chain Integration,” Proceedings of the Seventh Annual Conference of the
International Group for Lean Construction (IGLC-7), Berkeley, CA.
Tommelein, I., D. Riley, et al., 1998, “Parade Game: Impact of Work Flow Variability on Succeeding Trade Performance,” Proceedings of the Sixth Annual Conference of the International
Group for Lean Construction (IGLC-6), Guarujá, Brazil.
Tommelein, I. and M. Weissenberger, 1999, “More Just-In-Time: Location of Buffers in
Structural Steel Supply and Construction Processes,” Proceedings of the Seventh Annual
Conference of the International Group for Lean Construction (IGLC-7), Berkeley, CA.
Tsao, C., I. Tommelein, et al., 2000, “Case Study for Work Structuring: Installation of Metal
Door Frames,” Proceedings of Eighth Annual Conference of the International Group for Lean
Walbridge Aldinger, 2000, Lean Fundamentals, Detroit.
316
Walton, M., 1986, The Deming Management Method, New York, NY, Putnam Publishing.
Wild, R., 1995, Production and Operations Management, 5th Ed., London, Cassell Educational
Ltd.
Winch, G., 2003, “Models of Manufacturing and the Construction Process: The Genesis of ReEngineering Construction,” Building Research & Information, 31 (2), 107-118.
Womack, J. P. and D. T. Jones, 1996, Lean Thinking, New York, NY, Simon & Schuster.
Womack, J. P., D. T. Jones, et al., 1990, The Machine That Changed the World, New York, NY,
Rawson.
317
Glossary
Sources:
□
□
□
□
□
Lean Thinking, James P. Womack and Daniel T. Jones
The Encyclopedia of Operations Management Terms, Arthur V. Hill
Competing in World Class Manufacturing, Craig Giffi, Aleda V. Roth and Gregory M. Seal
Fundamentals of Production/Operations Management, Harold E. Fearon, W. Ruch et al.
Factory Physics, Wallace Hopp and Mark Spearman
Acceptable Quality Level (AQL)--A concept that states there is some nonzero level of
permissible defects.
Activity-Based Costing--Collecting cost data on all activities that occur rather than just the three
primary resources (materials, labor and machinery). This is an attempt to define the components
of burden. The objective of this system is to look at all areas where cost reductions can be made.
Aggregate Planning--The broad, overall decisions that relate to the programming of resources
for production over an established time horizon.
Batch and Queue--The mass production practice of making large lots of a part and then sending
the batch to wait in the queue before the next operation in the production process. Contrast with
single-piece flow.
Benchmarking--Refers to comparing one’s current performance against the world leader in any
particular area. In essence, it means finding and implementing best practices in the world.
Benchmarking is essentially a goal setting procedure.
Cells--The layout of different types of machines performing varied operations in a tight sequence,
typically in a U-shape, to permit single-piece flow and flexible deployment of human effort by
means of multimachines. Contrast with process villages.
Cellular Manufacturing--An approach in which manufacturing work centers (cells) have the
total capabilities needed to produce an item or a group of similar items.
Critical Path Method/Program Evaluation and Review Technique (CPM/PERT)--A method
for determining the critical path by examining the earliest and latest start and finish times for each
activity.
Cycle Time--The time required to complete one cycle of an operation. If cycle time for every
operation in a complete process can be reduced to equal takt time, products can be made in
single-piece flow.
Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM)--Engineering
designs created and tested using computer simulations and then transferred directly to the
production floor where machinery uses the information to perform production functions.
318
Concurrent (or Simultaneous) Engineering (CE)--Deals primarily with the product design
phase. The term refers to an improved design process characterized by rigorous up-front
requirements analysis, incorporating the constraints of subsequent phases into the conceptual
phase and tightening of change control toward the end of the design process. Compression of the
design time, increase in the number of iterations (i.e., increase in the frequency of information
exchange) and reduction in the number of change orders are three major objectives of concurrent
engineering.
Continuous Improvement--Associated with Just-in-Time (JIT) and Total Quality Control
(TQC), continuous improvement has emerged as a theme itself. A key to this concept is to
maintain and improve the working standards through small, gradual improvements. The inherent
wastes in the process are natural targets for continuous improvement. The term “learning
organization” refers partly to the capability of maintaining continuous improvement.
Cross Training and Job Rotation--Employees are rotated out of their job after a certain duration
and trained into a new job. They are not only trained how to do the job, but are also informed of
the quality and maintenance issues that go along with the job. The principle here is that an
employee with a well rounded background of how the company operates will be more valuable to
the company.
Distribution Requirements Planning (DRP)--The function of determining the need to replenish
inventory at branch warehouses over a forward period of time.
Economic Order Quantity (EOQ)--The optimal order quantity (batch size) that minimizes the
sum of the carrying and ordering cost.
Employee Involvement--Rapid response to problems requires empowerment of workers.
Continuous improvement is heavily dependent on day-to-day observation and motivation of the
work force; hence, the idea of quality circles. To avoid waste associated with division of labor,
multiskilled and/or self-directed teams have been established for product/project/customer based
production.
Five Whys--Taiichi Ohno’s practice of asking “why” five times whenever a problem was
encountered so that the root cause of the problem can be identified and effective countermeasures
can be developed and implemented.
Five S’s--Derived from the Japanese words for five practices leading to a clean and manageable
work area: seiri (organization), seiton (tidiness), seiso (purity), seiketsu (cleanliness) and
shitsuke (discipline).
Flexible Manufacturing--An integrated manufacturing capability to produce small numbers of a
great variety of items at low unit cost. Flexible manufacturing is also characterized by low
changeover time and rapid response time.
Flow--The progressive achievement of tasks along the value stream so that a product proceeds
from design to launch, order to delivery and raw materials into the hands of the customer with no
stoppages, scrap or backflows.
ISO 9000--A set of process quality standards developed by the International Organization for
Standardization and recognized worldwide.
319
Just-in-Time (JIT)--A system for producing and delivering the right items at the right time in the
right amounts. JIT approaches just-on-time when upstream activities occur minutes or seconds
before downstream activities, so single-piece flow is possible. The key elements of JIT are flow,
pull, standard work (with standard in-process inventories) and takt time.
Kaikaku--Radical improvement of an activity to eliminate muda; for example, reorganizing
processing operations for a product so that instead of traveling to and from isolated “process
villages,” the product proceeds through operations in single-piece flow in one short space. Also
called breakthrough kaizen, flow kaizen and system kaizen.
Kaizen--Continuous, incremental improvement of an activity to create more value with less
muda. Also called point kaizen and process kaizen.
Kanban--A small card attached to boxes of parts that regulates pull in the Toyota Production
System by signaling upstream production and delivery.
Lead Time--The total time a customer must wait to receive a product after placing an order.
When a scheduling and production system is running at or below capacity, lead time and
throughput time are the same. When demand exceeds the capacity of a system, there is
additional waiting time before the start of scheduling and production, and lead time exceeds
throughput time. Refer to throughput time.
Line Balancing--A means of balancing the appropriate amount of workers needed for a
production line by satisfying cycle time and precedence constraints.
Manufacturing Requirements Planning (MRP II)--A method for effective planning of all the
resources of a manufacturing company. Ideally, it addresses operational planning in units,
financial planning in money, and has a simulation capability to answer what-if questions.
Master Production Schedule (MPS)--A time-phased plan specifying how many units are
requested and when the firm plans to build each end item.
Material Requirements Planning (MRP)--A computerized system used to determine the
quantity and timing requirements for materials used in a production operation. MRP systems use
a master production schedule, a bill of materials listing every item needed for each product to be
made, and information on current inventories of these items in order to schedule the production
and delivery of the necessary items. Manufacturing Resource Planning (often called MRP II)
expands MRP to include capacity planning tools, a financial interface to translate operations
planning into financial terms and a simulation tool to assess alternative production plans.
Modular Design--Organizing a set of distinct components that can be developed independently
and then “plugged together.”
Muda--Any activity that consumes resources but creates no value.
Operation--An activity or activities performed on a product by a single machine. Contrast with
process.
320
Outsourcing--Procuring raw materials and components externally rather than creating them
internally.
Perfection--The complete elimination of muda so that all activities along a value stream create
value.
Period Order Quantity (POQ)--A lot sizing rule that defines the order quantity in terms of the
period’s supply.
Poke Yoke--A mistake-proofing device or procedure to prevent a defect during order taking or
manufacture. An order-taking example is a screen for order input developed from traditional
ordering patterns that questions orders falling outside the pattern. The suspect orders are then
examined, often leading to the discovery of input errors or buying based on misinformation. A
manufacturing example is a set of photocells in parts containers along an assembly line to prevent
components from progressing to the next stage with missing parts. The poke yoke in this case is
designed to prevent movement of a component to the next station if a light beam is not broken by
the operator’s hand in each bin containing a part for the product under assembly at that moment.
A poke yoke is sometimes also called a baka yoke.
Process--A series of individual operations required to create a design, completed order or
product.
Processing Time--The time a product is actually being worked on in design or production and
the time an order is actually being processed. Typically, processing time is a small fraction of
throughput time and lead time.
Processing Villages--The practice of grouping machines or activities by type of operation
performed; for example, grinding machines or order entry. Contrast with cells.
Pull--A system of cascading production and delivery instructions from downstream to upstream
activities in which nothing is produced by the upstream supplier until the downstream supplier
signals a need. The opposite of push. Refer also to kanban.
Quality Circles--Teams that meet to discuss quality improvement issues.
Quality Function Deployment (QFD)--A visual decision-making procedure for multiskilled
project teams that develops a common understanding of the customer’s voice and a consensus on
the final engineering specifications of the product that has the commitment of the entire team.
QFD integrates the perspectives of team members from different disciplines, ensures that their
efforts are focused on resolving key trade-offs in a consistent manner against measurable
performance targets for the product, and deploys these decisions through successive levels of
detail. The use of QFD eliminates expensive backflows and rework as projects near launch.
Queuing Theory--A branch of mathematics concerned with systems in which customers (orders,
calls, etc.) arrive and are served by one or more servers. Queuing theory models are usually
concerned with estimating the steady-state performance of the system such as the utilization, the
mean time in queue, the mean time in system, the mean number in queue and the mean number in
system.
321
Queue Time--The time a product spends in line awaiting the next design, order processing or
fabrication step.
Re-Engineering--The radical reconfiguration of processes and tasks, especially with respect to
implementation of information technology. Recognizing and breaking away from outdated rules
and fundamental assumptions is a key issue of re-engineering.
Right-Sized Tool--A design, scheduling or production device that can be fitted directly into the
flow of products within a product family so that production no longer requires unnecessary
transport and waiting.
Seven Muda--Taiichi Ohno’s original enumeration of the wastes commonly found in physical
production. These are overproduction ahead of demand, waiting for the next processing step,
unnecessary transport of materials (for example, between process villages or facilities), over
processing of parts due to poor tool and product design, inventories more than the absolute
minimum, unnecessary movement by employees during the course of their work (looking for
parts, tools, prints, help, etc.) and production of defective parts.
Single-Piece Flow--A situation in which products proceed, one complete product at a time,
through various operations in design, order taking and production, without interruptions,
backflows or scrap. Contrast with batch-and-queue.
Six Sigma--Structured application of the tools and techniques of TQM on a project basis to
achieve strategic business results. Sometimes defined as a failure rate of 3.4 parts per million.
Standard Work--A precise description of each work activity specifying cycle time, takt time,
the work sequence of specific tasks and the minimum inventory of parts on hand needed to
conduct the activity.
Standard Work Design--The design of each work activity specifying cycle time, work sequence
of specific tasks and minimum inventory of parts on hand needed to conduct the activity.
Statistical Quality Control (SQC)--Using statistical methods to identify, prioritize and correct
elements of the manufacturing process that detract from high quality.
Strategic Partnering--A structural management approach to facilitate teamwork across
contractual boundaries. With such coordination, construction companies may benefit from
reductions in delivery times, improved supplier responsiveness and improved quality of products
and services as well as reductions in costs.
Stock Keeping Unit (SKU)--A unique identification number (or alphanumeric string) that
defines an item for inventory.
Taguchi Methods--Developed to improve the implementation of TQC in Japan. They are based
on the design of experiments to provide near optimal quality characteristics for a specific
objective. The goal is to reduce the sensitivity of engineering designs to uncontrollable factors or
noise. Sometimes referred to as “robust design” in the United States.
322
Takt Time--The available production time divided by the rate of customer demand. Takt time
sets the pace of production to match the rate of customer demand and becomes the heartbeat of
any lean system.
Theory of Constraints (TOC)--A management philosophy that recognizes that there are very
few critical areas, resources or policies that truly block the organization from moving forward. If
performance is to be improved, an organization must identify its constraints, exploit the
constraints in the short run and, in the longer term, find ways to overcome the constraints (limited
resources).
Throughput Time--The time required for a product to proceed from concept to launch, order to
delivery or raw materials into the hands of the customer. This includes both processing and
queue time. Contrast with processing time and lead time.
Time Based Competition (TBC)--Refers to compressing time throughout the organization for
competitive benefit. Essentially, this is a generalization of the JIT philosophy.
Total Productive Maintenance (TPM)--Refers to autonomous maintenance of production
machinery by small groups of multiskilled operators. TPM strives to maximize production output
by maintaining ideal operating conditions.
Total Quality Control (TQC)--The difference between total quality management and total
quality control is epitomized by the phrase “management vs. control.” Most companies “control”
quality by a series of inspection processes, but “managing” quality is a continuous quality
improvement program. However, a good control system is the first step in the development of a
management system.
Total Quality Management (TQM)--An approach for improving quality that involves all areas
of an organization (sales, engineering, manufacturing, purchasing, etc.) with a focus on employee
participation and customer satisfaction. TQM can involve a wide variety of quality control and
improvement tools and emphasizes a combination of managerial principles and statistical tools.
Transparency/Visual Control--The placement in plain view of all tools, parts, production
activities and indicators of production system performance so that the status of the system can be
understood at a glance by everyone involved.
Value--A capability provided to a customer at the right time at an appropriate price, as defined in
each case by the customer.
Value Based Management (VBM)--Refers to conceptualized and clearly articulated value as the
basis for competing. Continuous improvement to increase customer value is one essential
characteristic of value based management.
Value Engineering--The systematic application of recognized techniques by a multidisciplined
team to identify the function of a product or service, establish a worth for that function, generate
alternatives through the use of creative thinking and provide the needed functions to accomplish
the original purpose of the project reliably and at the lowest life-cycle cost without sacrificing
safety, necessary quality and environmental attributes of the project.
323
Value Stream--The specific activities required to design, order and provide a specific product,
from concept to launch, order to delivery and raw materials into the hands of the customer.
Value Stream Mapping--Identification of all the specific activities occurring along a value
stream for a product or product family.
Visual Management (VM)--An orientation toward visual control in production, quality and
workplace organization. The goal is to make the applicable standard and any deviation from it
immediately recognizable by anybody. This is one of the original JIT ideas which has been
systematically applied only recently in the West.
Zero Defects--A concept introduced by Japanese manufacturers that stresses the elimination of
all defects. This contrasts with the idea of AQL.
324
Acknowledgments
Students
Sincere thanks to all of the students in the Construction Engineering and Management Program at
the University of Colorado who contributed work, thought and care to this project. Thanks to Jeff
Hlad, Travis Stewart, Spencer Won, Poon Thiengburanthum and Brian Saller and especially to
Mark Krewedl and Josh Balonick.
Practitioners
To those industry people who were so generous with their time and their knowledge - genuine
thanks go out to Greg Holroyd (Southland Industries), Remo Mastriani (Walbridge-Aldinger),
Paul Reiser (Boldt Industries) and Russell Batchelor (BAA).
Academics and Lean Theorists
Many others who studied lean manufacturing and lean construction contributed to this effort.
Thanks go out to Professor Glen Ballard, Greg Howell, Gene Lazaroff, Professor Iris Tommelein,
Professor Lauri Koskela, Professor Gary McCelland and Professor Jeffrey Luftig.
Former Team Members
And finally, Bob Knapp and Tom Searl contributed significantly to the early efforts of the team;
their involvement was most appreciated.
325

application of lean manufacturing principles to construction

Transcription

Similar documents

Since 2003, Beracah – meaning blessing – has

BVI Spring Regatta Brochure

JAY A. FERNANDO Vice-President Strategic Planning

Pat Murphy – Howth Yacht Club

Network Profile - Performance Media

69th Doolittle Raider`s Reunion Flyer

Proceeds go to support NJROTC scholarships and the Port

Join the Drive to Better Health