WDPF-to-Ovation upgrade

PROCESS CONTROL
2007 OUTAGE HANDBOOK
Lifecycle planning for your DCS
By Mitch Cochran, Process Control Solutions LLC
T
Support is available, but is focused
he advent of the distributed con- WDPF maintenance
strictly on maintenance—replacetrol system (DCS) in the 1980s
brought powerplant control into The WDPF control system has been
ment parts, repairs, and field serthe digital age, combined the on the market since the mid 1980s,
vice. Emerson encourages owners
formerly separate functions of control and is approaching the end of its
of products in this category to initiand data acquisition, and enabled product lifecycle (Fig 1). That’s not a
ate their lifecycle planning.
process data to be integrated with knock against the product. That’s a n “Retired products” are no longer
enterprise-wide business-manage- fact established by the manufacturer’s
available for purchase. Support
is limited, slower, more costly,
ment data. In the 1990s, DCS suppli- product-support policy. Emerson’s
and subject to material availabilers further enhanced their systems, policy is to provide a minimum of 10
moving away from proprietary hard- years of product support. The followity. Transition to “retired product”
status marks the end of the 10-yr
ware and software, and toward more ing definitions from the original equipproduct-support commitment.
inter-operable, standards-based ment manufacturer (OEM) apply:
The WDPF control system is clasnetworks. Net result: Today’s DCS n “Current products” are the most
is a reliable, user-friendly
sified as a “maintained
product that dominates
product,” and is quickly
the controls sector of the
approaching “retired prodelectric-power industry.
uct” status. At the manBut all products, no matagement level, therefore,
WDPF users should be askter how dominant, have
a finite lifecycle. This is
ing themselves: How long—
particularly true for microand at what O&M cost—can
I maintain my DCS? How
processor-based products.
much—and in what year—
Owner/operators of DCSs,
should I budget for a system
therefore, eventually must
address such lifecycle planupgrade?
ning problems as lack of
At the technician level,
manufacturer support,
users should be asking: Are
shortage of spare parts,
my system backups comand processor capacity limplete and up to date? What
can I do to be prepared for
itations. Lifecycle planning
a software server crash?
also involves evaluation of
Where can I get refurbished
budgetary constraints as
WDPF parts? Could I benwell as corporate strategies 1. Even the most reliable DCS eventually needs to be
regarding future expan- upgraded, because of such problems as lack of OEM supefit from having a plant
port and shortage of spare parts
simulator? What can I do to
sion.
alleviate memory capacity
This article discusses
lifecycle planning for one
limitations?
of the most popular DCSs in North
System backups. To prevent the
up-to-date products offered with
America—the WDPF (for Westingpublished pricing, normal lead loss of critical configuration software
house Distributed Processing Famtimes, and complete support. Cur- during a hardware or software failily), manufactured by Emerson Prorent products are recommended for ure, WDPF systems must be backed
new installations.
up properly. Recovering from a hardcess Management’s Power & Water
Solutions unit, Pittsburgh, Pa. Note n “Active products” have been func- disk crash on an operator WEStation
that Emerson purchased the former
tionally replaced by “current prod- is routine maintenance, requiring
Westinghouse Process Control Div
ucts,” but remain available with only a blank hard drive and the “boot
when Siemens AG acquired that
published pricing, normal lead net–install” procedure from the Softcompany’s power generation busitimes, and complete support. ware Load Kit U0-8001-2.x.
Active products are intended for
The software server, however, is
ness. Intent here is to help owners
expansion of existing systems. the most critical drop in the WDPF
of any make and model DCS decide
Transition to “active product” sta- system, since all other drops are
how long they should retain their
existing control system, and at what
tus marks the start of the 10-yr loaded from the software server. So
recovering from a hard-disk crash
point they should make the leap to a
product-support commitment.
new system—using the WDPF as an n “Maintained products” gener- on the software server is a much bigally are not available for purchase. ger deal. This requires Solaris and
example.
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WDPF Release CD-ROMs, back-up
tapes, third-party licenses, various
custom files and drivers, and more.
Many times, if proper back-ups have
not been maintained, recovery from
a hard-disk crash on the software
server cannot be accomplished completely.
The solution: Maintain a “hotspare” backup hard drive for the software server. With this action, even
the worst-case scenario—recovery
from a software server hard-drive
failure—becomes routine maintenance.
Serial interface QLC cards contain
configuration files in battery-backed
RAM memory. These files also must
be backed up to storage media, in
case a QLC card fails.
The WDPF is not self-documenting. Therefore, all logic drawings—
known as “SAMA” drawings because
they follow the Scientific Apparatus
Makers Assn standards—must be
maintained. An “as-built” drawing
review may be needed, in order to
bring your drawings up-to-date.
All of these maintenance tasks
should be performed, at a minimum,
during an annual inspection of the
WDPF system. At this time, preventive maintenance also should be
conducted on the WDPF hardware,
to prevent dust, soiling, or normal
wear-and-tear from impairing system reliability. The annual inspection also should include housekeeping tasks for the Unix file system,
and documentation of processor
memory.
Capacity limitations of the WDPF
system can hamper system operation and maintenance by making
it impossible to add or modify DCS
control logic, alarming, or monitoring
functions. Lack of available database
space in the distributed processing units (DPUs) and in the data
highway system IDs—referred to as
SIDs—are the most common capacity
problems encountered with a WDPF
control system.
One action that frees up database
memory is cleanup of the DPUs. This
work does not require any additional
hardware, and most of it can be done
offsite so that plant downtime is
minimized. The cleanup procedure
identifies and deletes unused points
and obsolete logic. It also identifies
alarmable points that could be moved
to an empty DPU. A total plant outage is not required to accomplish this
task.
Another option to alleviate capacity limitations is to add another
DPU processor to the system. Each
DPU comprises 120 kilobytes (kB)
of database space to which alarms
COMBINED CYCLE JOURNAL, Third Quarter 2006
from other DPUs could be re-located. Adding a DPU with cabinet and QCrates makes it possible to relocate
I/O points and control functions
from other DPUs, as well as moving
alarms.
Rebuilding the system point directory can alleviate the problem of
SIDs being “maxed out.” In addition
to identifying and deleting unused
points and obsolete logic, point broadcast frequencies will be optimized.
Preliminary steps can be performed
offsite on the DPU source code, but a
total plant outage of one to two days
is required to load the modified DPU
source code and rebuild the system
point directory.
Hardware maintenance. Several
options are available to users, when
it comes to hardware maintenance of
the WDPF system. Support from the
OEM includes:
n Emerson Sure-Serve Contracts.
The OEM offers repair and
exchange services designed to
accommodate varying needs and
delivery requirements.
n Standard Repair and Return.
Under this traditional scenario, customers return items for
inspection, test, and repair. It is
Emerson’s objective to service and
return all company-manufactured
items within 30 days of receipt.
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n 24-Hour Exchange. This option
is designed to address customer
needs in the event of an emergency or other critical situation. A
replacement item will be shipped
within 24 hours of receiving the
malfunctioning part. This level of
service can be provided only for instock items.
n Advance Replacement allows for
critical situations where you must
have a replacement item dispatched immediately. Once you call
for this service and your purchase
order or credit card is received,
a refurbished part, if available,
will be shipped to you. You will be
responsible to ship your serviceable item back to Emerson within
30 days.
Users also can tap several nonOEM suppliers of WDPF spare parts.
For example, Sun Microsystems and
HP parts—including RAM (random
access memory), hard drives, HP optical drives and optical discs, Ultra-5,
and Sparc-5 machines—can be purchased from Sun resellers. These
parts also can frequently be found
on E-Bay. Used hardware—including data-highway interface (DT Box)
and DPU hardware—is available
from resellers or customers who have
recently upgraded from WDPF. For
instance, DeepSouth Hardware SoluOH-82
tions LLC, Osyka, Miss, buys and
sells surplus WDPF parts for powerplant and turbine control systems.
Advanced simulators are invaluable tools for plant operator training. In addition to learning the basic
DCS windowing functions, trainees
can gain familiarity with normal
operating procedures—such as plant
startup and shutdown—and abnormal plant situations—such as feedpump trips, gas-turbine runbacks,
and so on.
Simulators also can serve as a
valuable maintenance tool. For
example, I&C technicians can use
them to build or maintain competency in such tasks as loop checks,
instrument calibrations, and testing
logic modifications prior to actual
implementation on the DCS. Finally, because the simulator runs on
standard control-system hardware,
it can double as a “hot-spare” parts
bin, thus improving DCS availability
when critical—and increasingly difficult to obtain—parts fail.
Time to upgrade
Despite the best efforts of the maintenance crew, a computer-based control
system eventually becomes obsolete,
and must be replaced. For WDPF
users, replacement options include
migration to Ovation retaining the QLine I/O, or a total system retrofit to
another DCS technology—such as the Siemens T3000, Foxboro, Bailey, and
Honeywell. A comprehensive controlsystem assessment will help users
decide when it’s time to upgrade. The
assessment might include:
n System capacity evaluation—an
evaluation of DPU memory and
system point directory capacity.
n Interviews with O&M personnel.
A questionnaire is a useful tool to
quickly assess the system hardware configuration. Interviews
with operators and maintenance
staff can help identify specific
areas that need improvement.
n Analysis of historical data. Operations logs and historical data can
be used to identify areas where the
control system should be optimized
or upgraded to improve plant availability, efficiency, or emissions.
n The Emerson System Assessment
Tool. End-users and owners of
WDPF systems can access Emerson’s automated assessment tool,
available on the web at www.wdpfusers.com, for help with their DCS
lifecycle planning.
Ovation option. Some power producers are doing away with the threeletter acronym that has for decades
dominated process control (DCS), in
COMBINED CYCLE JOURNAL, Third Quarter 2006
2007 OUTAGE HANDBOOK
2. PC-based process control is a DCS upgrade option—one particularly wellsuited for WDPF users because of Emerson’s “migration tool” that upgrades to
the Ovation system with a minimum of re-engineering and system retuning
favor of the two-letter acronym that
dominates the retail and residential
world—PC. Emerson seems to have
carried this concept the farthest, with
its Ovation product.
First released in 1997, Ovation is
a fully PC-based powerplant control
system that eliminates proprietary
operating schemes and vendor-specific hardware. According to Emerson,
Ovation reduces the risk of obsolescence often associated with proprietary control systems, and provides
better and more accessible information than is available through the
typical DCS.
For users of existing WDPF systems, an upgrade to Ovation can be
accomplished via a complete redraw,
or by using Emerson’s “migration
tool” which can simplify and speed up
the upgrade. The 36-MW San Gabriel
Mill Plant, Pomona, Calif, for example, completed its conversion from
WDPF to Ovation during a shutdown
lasting only one weekend.
The automated migration tool
enables owners of WDPF systems to
upgrade to the Ovation system with
minimal re-engineering and system
retuning (Fig 2). The tool quickly converts WDPF graphics and logic codes
to Ovation’s open architecture, avoiding the lengthy outages needed for
the typical modernization project.
Migration to the Ovation system
also can provide enhanced system
functionality and process efficiency while reducing risks related to
component obsolescence. If you are
considering upgrading your WDPF
system to Ovation, here are general
answers to a couple of the questions
you’re likely to ask:
Question 1: What are the pros
and cons of the migration tool, versus a complete redraw? Answer: The
migration tool converts the WDPF
DPU source code directly into Control Builder Sheets and database,
for import into Ovation. A one-to-one
change-out of DPUs is required. Also,
some upfront work may be required
to get the DPU source code into a
format that the migration tool will
accept. The migration tool offers a
well-proved migration path, and is a
good option if documentation is lacking, or if schedule or budgetary constraints dictate the pace of the DCS
upgrade.
By contrast, the “redraw” is exactly
what its name implies. The point
database is generated from the
WDPF as-built termination lists and
Q-Line I/O documentation, and the
Control Builder Sheets are redrawn
to match the as-built WDPF SAMA
logic drawings (Fig 3).
Performing a complete redraw is
more expensive because of the additional software engineering that’s
required. Two DPUs—which are
located side-by-side and perform the
same function—can be combined into
one controller both to help offset the
higher overall cost of a redraw project
and to improve control-system reliability. A redraw project also offers
several advantages over a migration
project, which should be considered
in your evaluation. These include:
n More readable SAMA logic. With
the migration tool, logic is broken
up into small bites in order to
match WDPF execution order, and
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PROCESS CONTROL
signal lines criss-cross the sheet in
a visually confusing way.
n Better control-system logic review.
With the migration tool, a comprehensive design review is not performed.
n Design modifications easily can be
integrated as part of the upgrade
process.
n Simulation testing can be performed.
To compare the costs of a migration versus a redraw, users may
request separate quotes from Emerson—one for a straight migration and
the other for a re-draw. An additional
quote from a third-party DCS consultant may be required for the as-built
documentation and/or simulation
development.
Question 2: Which operating
system should I choose—Solaris or
Windows? Answer: Solaris users
often are familiar with Unix and concerned about network security, while
Windows users want easy connectivity to the plant local area network
(LAN) and inexpensive, off-the-shelf
computer parts. Other benefits of
Solaris include easy recovery from
hard-drive failures—with the “boot
net–install” option—and X-Windowing capability—via Hummingbird
Exceed. On the other hand, Windows
has Expanded Engineering Toolbox
functions, which are excellent.
Ovation redraw project
A typical WDPF-to-Ovation redraw
project includes the following elements:
n Plant walk-down and drawing
collection. A thorough review of
the DCS process graphics is performed, in conjunction with a plant
walk-down, to gain familiarity
with the plant systems. Master
red-line drawings (SAMA, P&IDs,
electrical schematics) are collected.
Also, the WDPF software server
configuration, along with custom
trend groups and any third-party
software licenses—such as for
Applix, optical drives, and printers—is documented and backed up
for future reference.
n As-built SAMA logic drawings are
the starting point for the software
design. Logic drawings are extracted from DPU source code.
n As-built termination lists and QLine Card slot assignments and
addressing documentation will
be generated and validated. This
information is entered into the
Ovation DBID Tool (Database
Initial Definition) to generate the
initial Ovation point database.
n Network layout/Ovation system
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PROCESS CONTROL
2007 OUTAGE HANDBOOK
3. A redraw project is an alternative to “migrating” to the Ovation system. It typically is more expensive because of the
additional software engineering that’s required, but its benefits include more readable SAMA logic drawings and a better
control-system logic review
architecture design. Fiberoptic
runs between buildings and turbine enclosures provide isolation
from electromagnetic interference
and eliminate grounding issues.
The 10-BaseT connections make
for flexible system architecture.
The number and physical locations
of fiber runs and network switches
must be determined.
n Ovation hardware order. Based
on the WDPF system hardware,
software design requirements,
and Emerson’s recommended network layout, the Ovation system
hardware order can be placed. The
Q-Line I/O hardware need not be
replaced, only the human-machine
interfaces and the DPU multi-bus
chassis and power supplies.
n Spare parts are more economical
if complete controller upgrade kits
are specified, rather than individual parts. Also, a simulator using
Ovation hardware could double as
a “hot-spare” parts bin.
n WEStation graphics. Newer WDPF
systems with WEStation graphics require no additional graphics
work. Older WDPF systems with
“classic graphics” require a redraw
of the process graphics.
n Simulator design. A simulator
model will be developed in order to
debug the Ovation software.
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n Final design review. Based on the
interviews with O&M personnel,
review of historical data, and logic
review, control-logic modifications
or additions to improve plant reliability, efficiency, or emissions
are reviewed and included in the
software design. Any additions or
modifications to the logic may need
to be reflected in the I/O termination lists and process graphics as
well.
n Software submittal to Emerson.
All documentation, along with the
Software Server backup tape, will
be submitted to Emerson and used
to implement the Ovation software.
n Software validation testing. A total
plant simulator model facilitates
debugging of the software design
and implementation. The “loopback stimulator” reads the outputs
from the control system, simulates
the process response, and writes
the inputs to the control system.
A detailed test procedure is an
invaluable tool that helps maximize simulation time and ensures
that nothing is missed. While the
purpose of the simulation test is
to validate the software design,
maintaining the simulator at the
plant for operator training and
as an engineering tool may be an
attractive option. This could be
done with “virtual controllers” or
using actual Ovation hardware.
Installation,
commissioning
For both redraw and migration projects, the installation of Ovation’s
fiberoptic network can be completed
prior to the plant outage in which the
total system installation occurs. After
all systems are locked out and tagged
out, the DPU processors, power supplies, WEStations, and WDPF Highway Interface Boxes are removed and
the Ovation controllers and WEStations are installed and downloaded.
With proper planning, a WDPF-toOvation upgrade can be completed
during a normal gas-turbine combustor inspection outage—even on a
large 2 × 1 combined-cycle plant.
Commissioning activities are subject to many factors—such as price
of fuel and dispatch requirements.
Some “hot” commissioning activities
include: pre-start simulations, false
fire, first sync, load-ramp tuning,
and load rejections. Documentation
and closeout of the upgrade project
includes point database backup,
software server backup to tape, and
printing the as-built control builder
logic. ccj oh
COMBINED CYCLE JOURNAL, Third Quarter 2006