Maintaining and Repairing Propane Fuel Systems on Stationary

Transcription

Maintaining and Repairing Propane
Fuel Systems on Stationary Engines
Maintaining and Repairing Propane
Fuel Systems on Stationary Engines
_______________________________________________________________________
Readers of this material should consult the law of their individual jurisdiction for the codes, standards,
and legal requirements applicable to them. This material merely suggests methods that the reader may
intended nor should it be construed to:
(1) Set forth procedures that are the general custom or practice in the gas industry.
(2) Establish the legal standard of care owed by propane distributors to their customers.
(3) Prevent the reader from using different methods to implement applicable codes, standards,
or legal requirements.
This material is designed to be used as a resource only to assist expert and experienced supervisors
and managers in training personnel in their organizations and does not replace federal, state, or
company safety rules. The user of this material is solely responsible for the method of implementation.
The Propane Education & Research Council, Frey Associates Inc., and the Alternative Fuels Research &
Education Division of the Railroad Commission of Texas assume no liability for reliance on the contents
of this training material. Issuance of this material is not intended to nor should it be construed as an
undertaking to perform services on behalf of any party either for their protection or for the protection
of third parties.
_______________________________________________________________________
All rights reserved. No part of this text may be reproduced, utilized, or transmitted in any form or by
any means, electronic or mechanical, including photocopying, recording, or by any information storage
and retrieval system, without permission in writing.
© Propane Education & Research Council (2008)
ABOUT THE PROGRAM
Of the energy sources available to the agricultural community, propane offers a desirable combination
of characteristics for agricultural applications.
Propane is among the most attractive options for reducing greenhouse gas emissions.
It is readily available.
It represents a proven and stable energy value.
Two of propane’s most important uses are providing electrical power, sometimes called “distributed
generation,” and power to operate irrigation pumps. Both of these applications utilize propane to fuel
stationary engines.
Keeping the propane fuel systems of these stationary engines in proper working order is a task that requires
a working knowledge of the characteristics of propane as a fuel and of the components of propane engine
fuel systems. This training program is intended to provide technicians with an introduction to propane
Air-cooled engines, often called “small engines” and used in electrical generators.
Liquid-cooled engines, typically used with larger electrical generators and irrigation pumps.
blue or red type in the text of this publication are given in
the glossary section (Appendix A) at the end of the instructional guide. Blue terms are concepts or
performance measures used to describe engine operation. Red terms are components of a propane
engine fuel system.
Acknowledgments
The Propane Education & Research Council (PERC) and the National Propane Gas Association
(NPGA) gratefully acknowledge the cooperation and contribution of the following individuals and
organizations for providing personnel, equipment, and technical assistance.
Mitch Torp and Glen Hale
TGP West Inc., 3250 El Camino Real, Suite 3, Atascadero, CA 93422 (805) 465-2849
www.tgpwest.com
Rich Fisher and Dave Campbell
Continental Controls Corporation, 8845 Rehco Road, San Diego, CA 92121 (858) 453-9880
www.continentalcontrols.com
Franz Hofmann
Railroad Commission of Texas, Alternative Fuels Research & Education Division,
6506 Bolm Road, Austin, Texas 78721 (512) 463-8501
[email protected]
Richard Dlugosz
Sherwood Valve, (888) 508-2583 www.sherwoodvalve.com
Members of the PERC Agriculture Advisory Committee and Stationary Engine Project Subcommittee
who served as subject matter experts (SMEs) and reviewers
A special thank-you goes to Michelle Swertzic, formerly of the Nebraska Propane Gas Association, for
Table of Contents
1.0 Physical Properties of Propane and Safety Precautions to Apply
1
2.0 Characteristics of Propane Fuel Systems for Stationary Engines
11
3.0 Propane-Fueled Stationary Engine Emission Control Systems
23
4.0 Propane-Fueled Engine Fuel System Maintenance and Repair
37
Appendix A: Glossary of Terms
75
Appendix B: Referenced Publications and General Information
79
Appendix C: Educational Materials
91
1.0
Physical Properties
of Propane and Safety
Precautions to Apply
1
1.0
INTRODUCTION
Working safely to maintain or repair propane fuel systems on stationary engines requires
service personnel to be familiar with propane’s physical properties and aware of safety
precautions.
The objectives of this chapter are to:
1.1 Identify the physical and combustion properties of propane.
1.2 Identify hazards associated with a release of propane.
1.3 Demonstrate safety measures to apply when working with propane engine fuel systems.
IDENTIFYING THE PHYSICAL AND COMBUSTION
PROPERTIES OF PROPANE
General Properties of Propane
Material Safety Data Sheet (MSDS) must be available
and accessible to all employees in the workplace where
hazardous materials are transferred, stored, or used. The
MSDS for propane is available from propane suppliers or
distributors. A complete MSDS for propane can be found
in Appendix B of this manual.
MSDS that relates to maintaining propane engine fuel
systems. The propane stored in containers can be either a
liquid or gas. To permit the storage and transportation of
propane in liquid form at temperatures warmer than its
boiling point (–44°F), pressure-tight containers are used.
Propane liquid stored in these containers at temperatures
at or above –44°F will vaporize and expand to pressurize
the vapor space inside of the container. This vapor
pressure naturally forces the propane from the container
to the gas utilization equipment. Propane’s liquid volume
and container vapor pressure varies with its temperature.
On a hot summer day, container vapor pressure may
approach 200 pounds per square inch; on a cold winter
day, it might be as low as 25–30 pounds per square inch.
(See the chart on the next page.)
2
Physical Properties of Propane and Safety Precautions to Apply
In its natural state, propane is colorless and odorless.
To increase the likelihood that a propane leak can be detected, an odorant (ethyl mercaptan)
is added to propane. This odorant is added to allow propane to be detected by smell long
before a combustible mixture is present.
Learn to recognize the odor of propane and always be sensitive to the slightest gas smell.
The Propane Education & Research Council (PERC) has produced consumer safety education
and warning brochures that incorporate an odorant “scratch-n-sniff” patch.
Contact PERC or your propane supplier to obtain these brochures to test your sense of
smell and verify that you can sense the presence of the odorant. See Appendix B for more
information on these brochures.
Be aware that under certain rare conditions, the intensity of the odorant may diminish or
fade. Some people may not be able to smell the odorant. While no odorant will be completely
affective as a warning agent in every circumstance, the odorant generally used in the propane
industry has been recognized as an effective odorant.
If for any reason you or fellow employees cannot smell odorized propane, immediately notify
your supervisor. Your safety and the safety of fellow workers may depend on your ability to
smell propane in the event of a leak. For additional information on the odorant, refer to the
Propane MSDS in Appendix B.
3
1.0
Combustion Properties of Propane
A propane molecule consists of three (3) carbon atoms and eight (8) hydrogen
atoms. Since carbon and hydrogen are readily burned when combined with
oxygen in air and an ignition source, propane is an excellent fuel. Its motor fuel
properties may be better understood when it is compared to gasoline, as shown
in the following table.
PROPERTY
GASOLINE
PROPANE
ENGINE FUEL CHARACTERISTICS
Formula
C8H18
C 3H 8
High carbon fuels are better conductors of electrical
energy. Thus propane requires more electrical energy
(spark) to ignite the fuel / air mixture. Low carbon fuels
have lower CO exhaust emissions.
Octane (R + M) / 2
82–93
95–104
With octane being a measure of a fuel’s resistance to
knock, propane can stand higher compression pressure
and more initial advanced spark timing than gasoline.
Energy Density
(Btu / Lb)
Lower
Higher
(Btu / Gal)
19,000
20,360
114,000
19,920
21,650
91,500
(Btu / Cu Ft)
Lower
Higher
Not Applicable
Not Applicable
2488
2520
3.5
1.5
Both fuels’ vapors are heavier than air (1.0).
0.739
0.51
In liquid form, both gasoline and propane are lighter
than water (1.0).
Boiling Point
80° to 440°F
–44°F
Above –44°F, propane becomes a vapor in open air.
Flammability
Limits
1.4% to 7.6%
gas-in-air
2.37% to 9.5%
gas-in-air
combustible mixture to the richest combustible mixture.
Stoichiometric
Combustion Air :
Fuel Required by
Weight
14.7 : 1
15.5 :1
High hydrogen-to-carbon ratio fuels produce more heat
per pound.
High carbon-to-hydrogen ratio fuels have more heat
energy per gallon.
(Vapor)
(Liquid)
4
Stoichiometric combustion is the ideal combustion
process during which a fuel is completely burned.
IDENTIFYING THE HAZARDS PRESENTED BY A RELEASE
OF PROPANE
If propane liquid is released into the air, it quickly
vaporizes, expanding to 270 times its original volume.
Therefore, a liquid propane leak can be more hazardous
than a vapor leak due to the expanding vapor cloud.
Also, when liquid propane is released into the atmosphere,
its rapid vaporization causes a refrigerating effect that
makes everything it touches extremely cold. If it comes in
contact with skin or other tissues, it will cause third-degree
freeze burns.
Propane is nontoxic, but will displace air if released into a
Propane vapor is 1.5 times heavier than air. If released into still air, it may initially
outside, the vapor should dissipate in the air.
When the physical and combustion properties of propane are considered together, these
Chemical hazards
Although propane is not toxic, under certain conditions it can present a danger by
displacing air required for breathing.
Mechanical hazards – Propane is stored under pressure — uncontrolled release can
Temperature hazards – Exposure of bodily tissues to liquid propane results in a
refrigerating effect, causing immediate freezing of tissues with symptoms similar
to frostbite.
Protecting yourself from these hazards requires the use of proper procedures and may require
the use of personal protective equipment, depending on the tasks you are performing.
5
1.0
Department of Labor (DOL) and/or
Occupational Safety and Health Administration
(OSHA) regulations require that proper
personal protective equipment (PPE) be worn
when procedures do not eliminate hazards
associated with the work being done. Your
employer is required to determine what PPE
is required, provide training on when and
how to use it, and verify that you are using it
as required. Generally, propane PPE includes
special vinyl gloves resistant to the actions
of propane, and eye or face protection is
appropriate for transferring propane and for
purging propane from pressurized storage or
fuel system components.
Vinyl Gloves
Safety Glasses
Acoustical Ear Muff and Ear
Plugs for Hearing Protection
Determine if a Propane Supply Tank is Used for Liquid or for
Vapor Service or for Both
Most stationary engines used
in agricultural applications will
be supplied propane from the
same type of tank used to supply
propane for farm or ranch
building heat. In the propane
industry this type of tank is
often called a “domestic” or
“residential” ASME tank.
Such tanks are built to comply
with the American Society of
Mechanical Engineers Code for
Pressure Vessels.
Typical ASME Tank Valve and Fitting Connections
A domestic ASME tank is
typically used to supply propane
vapor through the vapor
pressure regulator. It may also
be used to supply propane
liquid from the tank if a supply
valve is connected to the liquid
withdrawal valve opening.
6
Tank Valves and Fittings Connected
to the Tank’s Vapor Space
Tank Liquid Withdrawal Excess Flow
Valve. If a valve is installed here, it is
connected to the tank’s liquid space.
Procedures for Controlling Propane Hazards During
Purging Operations
In most cases, purging propane from engine fuel systems and reducing internal component
pressure to atmospheric pressure does not involve a large volume of propane.
Step 1:
Verify Ignition Sources Are
Eliminated or Controlled.
Inspect the area where the purged propane
will be directed during the purging process.
Be sure that propane is only released
that contains no ignition sources. Verify
that the engine is shut down and that
starting controls are locked out and/
or tagged out according to company
procedures. Always remove the start-run
key and disconnect the negative battery cable.
Step 2:
Close the Fuel Supply Valve(s) on the Propane Tank.
a. Close any liquid service valve(s) that
cooled engines used to drive irrigation
pumps or large electrical generators.
b. Close any vapor service valve(s) that
engine.
7
1.0
Step 3:
Close Any In-line Valve(s) Installed
Near the Fuel System Pressure
Regulator or Converter.
Determine if any in-line fuel valves
are located in the fuel piping system to
element replacement.
If present, close any and all in-line
fuel valves.
Step 4:
Outdoors, Loosen and Partially Disconnect a Union or Other Propane
Supply Line Swivel Fitting.
Wearing suitable personal protective equipment and working outdoors at
the propane supply tank, use the correct sized wrench to loosen the fuel line
connection at the closed vapor or liquid service valve(s), whichever applies.
8
Step 5:
After the Initial Venting of Product and Reduction of Pressure, Open
Any In-Line Valve(s) Closed in Step 3, Then Slowly Disconnect the
Fitting to Ensure Pressure Is Relieved.
Step 6:
Verify Entire Fuel System Pressure Is Reduced to Atmospheric
Pressure.
1.0
Lab Activity
Demonstrate Safety Measures to Apply When
Working on Propane Engine Fuel Systems
Directions: Complete each task to demonstrate proper safety measures for
venting and de-pressurizing a propane engine fuel system.
for Valve B shown below, place a in the box next to the correct answer.
O Propane Liquid O Propane Vapor
O Propane Liquid O Propane Vapor Valve B.
Valve A.
2. Applying your employer’s procedures, identify Personal Protective Equipment (PPE)
to use when purging propane from propane fuel lines and reducing propane pressure
to atmospheric pressure prior to disassembling a component in the fuel system.
For PPE A, B, and C, shown below, place a in the box below each correct answer
for the listed purging operation.
A.
Purging liquid propane (high pressure)
Purging propane vapor (reduced pressure)
B.
C.
Vinyl
Gloves
Eye
Protection
Hearing
Protection
O
O
O
O
O
O
9
1.0
3. Determine the safest area to vent purged fuel gas when preparing to disassemble a
propane fuel system component. On the diagram shown below, place the following
lettered items in the best location on the diagram to indicate steps in purging propane
from the fuel system and de-pressurizing the system.
a.
b. Location for purging propane in a well-ventilated area away from ignition sources.
c. Location to verify that propane pressure has been reduced to atmospheric pressure.
10
2.0
Characteristics of
Propane Fuel Systems
for Stationary Engines
11
2.0
INTRODUCTION
A working knowledge of propane engine fuel systems begins with identifying the components
that make up the system and how the components differ from smaller air-cooled engines to
larger glycol-water mixture – cooled engines.
2.1
Identify how the propane boiling process operates in a fuel supply container.
2.2
Identify the components of a propane fuel system for a small air-cooled engine.
2.3
Identify the components of a propane vapor fuel system for a large engine that is
glycol-water mixture-cooled and propane is vaporized in the fuel supply tank.
2.4
Identify the components of a propane vapor fuel system for a large engine that is glycolwater mixture-cooled and propane is vaporized in a fuel system component.
2.5
Identify the characteristics of a propane fuel system for a large engine in which the
propane is injected into the engine in either a vapor or liquid state.
2.6
Identify the primary codes and safety standards that apply to propane installations.
IDENTIFYING HOW THE PROPANE BOILING PROCESS
OPERATES IN A FUEL SUPPLY CONTAINER
Boiling: The change of physical state from liquid to vapor
Unlike gasoline or diesel engine fuel systems, most propane and natural gas engine fuel systems
process a dry gas (vapor state) fuel and combine it proportionally with air to provide the
engine’s combustion mixture. This dry gas characteristic of natural gas and propane fuels is
due to their relatively low boiling points at atmospheric pressure. Conversely, gasoline and
diesel are handled as liquids at atmospheric pressure due to their relatively high boiling points.
A material’s boiling point is the temperature at
atmospheric pressure required for the material to change
from its liquid state to its vapor state. Following are some
facts about the storage, handling, and use of propane as a
fuel help in understanding propane fuel systems.
Energy in the form of heat and pressure tends to reach
a point of equilibrium in a sealed storage container at
temperatures above a liquid’s boiling point; boiling of
liquid and vapor and, the balance of heat and pressure
forces results in the ceasing of vaporization.
12
Characteristics of Propane Fuel Systems for Stationary Engines
If vapor is withdrawn from a propane storage
container, the decrease in container pressure allows
boiling to resume, converting liquid
to vapor.
A change of state requires energy input in the
form of heat.
Because heat for vaporization is transferred to the
propane liquid from the air surrounding the container
through the metal wall of the fuel tank, there are
limits on a propane storage/supply container’s
a. Wetted surface area — As the amount of
liquid in a fuel tank decreases, heat exchanger area decreases.
As heat transfer decreases, the rate and amount of liquid vaporization decreases.
b. Air temperature — Heat needed for vaporization is transferred from the
air surrounding the fuel tank. In colder weather the rate and amount of liquid
vaporization decrease compared to vapor available in hot weather.
c. High air humidity and tank refrigeration — As propane vaporizes, the tank
surface is refrigerated. High relative humidity (water-saturated air) may result in
water condensation — or in colder conditions — water freezing on the tank. Either
condition will reduce the rate of vaporization and volume of vapor available for fuel.
IDENTIFYING THE COMPONENTS OF A PROPANE FUEL
SYSTEM FOR A SMALL AIR-COOLED ENGINE
Standby or dedicated electrical power generators represent a
widespread application for small propane-fueled stationary
engines. Farm and ranch operators located in moderate
vapor to the generator engine.
The principal components of a small engine supplied with
propane vapor from a tank are illustrated in the diagram
on the next page.
Courtesy of Marathon Engine Systems
13
2.0
Typically, on small air-cooled engines [25 brake horsepower (bhp) and smaller], vapor fuel
systems are used, where the fuel is vaporized in the fuel tank and reduced to a pressure
suitable for the propane-air mixing devices. Fuel demand for these engines is usually small
enough for vaporization of liquid propane to be provided by the storage/supply tank. A
pressure regulator installed at the tank decreases tank vapor pressure to approximately 5 to
10 psig pressure to downstream piping. Depending on the installation and manufacturer’s
instructions, an optional line service pressure regulator may be installed to further reduce
inlet pressure supplied to the electric lock-off valve.
A fuel lock-off valve, operated by engine vacuum or electrical current from the engine ignition
operating.
In a typical small engine propane fuel system, a pressure reducing valve is installed
downstream of the lock-off valve and upstream of the propane-air mixer to provide propane
vapor at a negative pressure. Mixing of propane vapor and air for combustion is done in the
propane-air mixer in response to the negative pressure of the engine’s piston intake stroke.
14
IDENTIFYING THE COMPONENTS OF A PROPANE VAPOR FUEL
SYSTEM FOR A LARGE GLYCOL-WATER MIXTURE-COOLED
ENGINE WHERE PROPANE IS VAPORIZED IN THE FUEL TANK
Engines larger than 25 brake horsepower typically produce heat exceeding the cooling ability
of air passing over and around the combustion cylinders. Liquid circulating through a radiator
and jackets surrounding the cylinders is required to prevent lubrication breakdown and
engine damage.
Although a number of stationary engines used to power electrical generators in the 15–25 kW
output range require liquid cooling, their propane vapor requirements often do not exceed
the vaporizing capacity of a 500-water-gallon-capacity propane tank (depending on location
factors). For these installations, the propane fuel system diagram shown on the previous page
would be suitable.
For larger engines, one or more 1,000-water-gallon-capacity propane supply tanks may be
required to meet engine vapor demand. The fuel system diagram shown above is typical for
larger displacement irrigation pump engines.
15
2.0
IDENTIFYING THE COMPONENTS OF A PROPANE VAPOR
FUEL SYSTEM FOR A LARGE GLYCOL-WATER MIXTURE COOLED ENGINE WHERE PROPANE IS VAPORIZED IN A
FUEL SYSTEM COMPONENT
Larger engines requiring propane vapor in quantities that exceed the vaporization capacity of
a typical propane storage tank require a vaporizer outside of the fuel tank. A typical propane
Important Propane Fuel-System Components
There are requirements for LP-gas hose or metallic piping conveying propane
LP-Gas Hose
a. Underwriters Laboratories, Inc. (UL) listed wire-braid stainless steel approved for
LP-gas service.
b. Must be able to withstand pressures of 5 times 35o psig working pressure (1750 psig
burst pressure).
c. Manufacturer name, product code, size, and pressure rating must be continuously
marked on the hose cover.
d. Typically #6 hose (5/16-inch nominal inside hose diameter).
16
Metallic Piping
a. Welded schedule 40 steel pipe is approved for liquid or vapor service not exceeding
supply container pressure. (Threaded schedule 40 pipe is not permitted for conveying
propane liquid or vapor at container pressure).
b. Threaded schedule 80 steel pipe is approved for liquid or vapor service.
c. Buried metallic piping must have adequate corrosion protection.
Hydrostatic Protection for Liquid Piping or Hose
a. A hydrostatic relief valve must be installed in any section of LP-gas piping or hose
conveying liquid propane that can be shut off at each end.
b. Hydrostatic relief valves must have a pressure setting of not less than 400 psig or more
than 500 psig.
Vacuum Lock-Off / Fuel Filter
This component serves two functions.
1. Liquid Propane Shutoff – Acting as a
safety device, the vacuum-operated lock-off
engine is not running. Interruption of negative
pressure (–0.2 inch water column) from the
fuel-air mixer air valve closes the internal
valve.
2. Fuel Filter –
and screen at the top of the cutaway body
picture remove solids such as pipe scale
from the liquid propane — material that
might damage regulator discs or plug valve
pressure regulators.
Cutaway View of Vacuum Lock-off Filter
17
2.0
Converter — Vaporizer/Pressure
Regulator
This component also serves two functions.
1. Liquid Propane Vaporizer — For
engines requiring propane vapor that
exceeds supply tank vaporizing capacity,
the converter uses engine coolant liquid to
assure adequate propane vapor is supplied.
A number of converter models are available.
Two things must be considered in the
selection of the proper model for a given
engine and application.
Converter for Engines up to 110 Brake Horsepower
Examples: 1.5L Inline 4-Cylinder Through
4.3L V-6 Engines
Engine displacement — volume of
all cylinders.
Vapor-combustion air mixture demand
throughout the engine’s power range.
Converter for Engines up to 350 Brake Horsepower,
up To and Including 8L Engines
The cutaway drawing to the
Propane liquid (darkest blue)
entering the vaporizer where
it meets the primary pressure
seat. At this point, propane
pressure is reduced from tank
pressure to approximately
1½ to 3 psi.
Heat is transferred from the circulating coolant (green) through metal jacket walls into
the vaporizing liquid (medium blue).
18
2. Vapor Pressure Regulator – After the propane passes through the primary pressure
The second-stage operating pressure is negative in response to negative pressure from the
engine. Propane vapor is not supplied to the propane-air mixer under positive pressure.
It is reduced to a
second-stage pressure
of –0.5 to –3.5 inches
water column.
Propane-Air Mixer
In the illustration
shown at right, a
propane-air mixer is
mated to a throttle
body, making a
complete propane
carburetor assembly.
A propane-air mixer
is shown below. A
cutaway view of a
propane carburetor is
shown at bottom right.
IMPCO Model 100 Propane-Air Mixer for Engines
up to 106 Brake Horsepower
IMPCO Model 125 for Engines up to
126 Brake Horsepower
19
2.0
Propane-air mixers illustrated on the previous page operate on the principle of pressure
differential. Pressure differential operates when pressures are not equal on both sides of a
diaphragm, and in response, the diaphragm moves to the side with the lower pressure.
pressure from one side to the other. The resulting pressure differential moves the diaphragm
and the attached gas valve in proportion to the amount of air entering the engine.
Movement of the gas valve then allows a predetermined amount of propane vapor out of the
mixer to enter the air stream. The fuel mixes with air due to the turbulence generated by the air
and fuel changing direction several times as the engine intake valves open and close. Idle fuel
mixture is typically adjustable by setting a needle valve
screw located on the carburetor body.
Propane fuel systems and components illustrated and
discussed to this point are generally used on small to
moderate-sized stationary engines.
Clean Air Act regulations that apply to larger stationary
discussed in a later section of this manual. Propane
fuel-system components for some stationary engine
applications may utilize components such as the variable
load mixer shown to the right. Mixers of this type more
closely control gas-to-air ratios in response to electronic
signals from an exhaust manifold oxygen sensor and
electronic control module.
Continental Controls Corp EGC2
Electronic Gas Carburetor for Lean
Burn Engine missions Control
IDENTIFYING THE CHARACTERISTICS OF A PROPANE
FUEL SYSTEM FOR A LARGE ENGINE WHERE THE PROPANE
IS INJECTED INTO THE ENGINE IN EITHER A VAPOR OR
LIQUID STATE
Propane fuel systems based on injection of propane in either a gaseous or liquid state have
approaches developed for spark-combustion engines, the direct injection method appears to
offer the possibility of lower yield of undesired emissions, increased fuel economy, and engine
propane injection seems to offer. Consequently, propane injection systems are not currently
offered for stationary engine applications. Stationary spark ignition engines function well with
20
Continuous loading, resulting in relatively constant intake and manifold pressures.
Relatively constant engine rpm, resulting in relatively constant air-fuel demand and
mix ratio.
No change in altitude while operating, resulting in smaller changes in combustion air
density, etc.
Vehicle engines, by contrast, with their constantly changing combustion processes, may
IDENTIFYING THE PRIMARY CODES AND SAFETY
STANDARDS THAT APPLY TO PROPANE INSTALLATIONS
The following codes and standards should be consulted when planning a stationary engine
National Fire Protection Association (NFPA), 1 Batterymarch Park, Quincy, MA 02169-7471
www.nfpa.org
NFPA 10 Installation, Maintenance, and Use of Portable Fire Extinguishers
NFPA 30 Flammable and Combustible Liquids Code
NFPA 37 Stationary Combustion Engines and Gas Turbines
NFPA 70 National Electrical Code
Perhaps the most important of the NFPA publications listed above, and the one most directly
related to propane engine fuel systems, is NFPA 58. In addition to NFPA standards, the
following information pertaining to the installation and use of standby electrical systems
Article X, National Building Code, available from the American Insurance Association,
85 John Street, New York, N.Y. 10038
Agricultural Wiring Handbook, obtainable from the Food and Energy Council,
909 University Avenue, Columbia, MO, 65201
ASAE EP-364.2, Installation and Maintenance of Farm Standby Electric Power,
available from the American Society of Agricultural Engineers, 2950 Niles Road,
St. Joseph, MI 49085
21
2.0
2.0
Lab Activity
Identify the Components and Their Functions
on Typical Propane Engine Fuel Systems
Directions: Complete each task to demonstrate your ability to identify
components of a propane engine fuel system.
1. Fill in the numbered blanks in the diagram shown below to identify major components of a propane engine fuel system that uses propane vaporized in the supply tank.
2. Fill in the numbered blanks
in the diagram below to
identify major components of
a propane engine fuel system
that uses propane vaporized
in a fuel-system component.
22
3.0
Propane-Fueled
Stationary Engine
Emission Control Systems
23
3.0
INTRODUCTION
To minimize the production of undesirable exhaust emissions and to maximize the useful
work that can be obtained from an internal combustion engine, an engine emission control
system may be required. Federal and state environmental regulations may apply to new or
certain existing installations of stationary engines. Service personnel who are called upon to
maintain or repair stationary engines should understand the functions provided by emission
control system-equipped engines.
3.1
Identify the department of the U.S. government that enforces the Clean Air Act by
publishing regulations that address internal combustion engine emissions.
3.2
Identify the meaning of “stoichiometric combustion” and the ideal mixture ranges of
propane-air fuel mixtures that tend to yield the lowest quantities of carbon monoxide
and oxides of nitrogen.
3.3
Identify the general operating characteristics of an electronic emission control system,
and the typical components of a system.
3.4
In relation to emission control system operations, identify the meaning of “open loop”
and “closed loop.”
THE ROLE OF THE U.S. ENVIRONMENTAL PROTECTION
AGENCY (EPA) IN REGULATING STATIONARY ENGINE
EXHAUST EMISSIONS
Identifying EPA’s enforcement role for the Clean Air Act
The U.S. Congress established and charged the Environmental Protection Agency (EPA)
with responsibility to create and enforce regulations in support of the Clean Air Act.
EPA’s regulations are found in Title 40 of the Code of Regulations, and can be accessed on
the internet via www.epa.gov
at http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&tpl=%2Findex.tpl.
24
Propane-Fueled Stationary Engine Emission Control Systems
An example of a GPO Web page with links to
the EPA Clean Air regulations is shown to the
right. These important regulations affect the
installation, maintenance, and repair of spark40 CFR part 60, subpart JJJJ.
40 CFR part 63, subpart ZZZZ.
40 CFR part 1048 — Control of Emissions
From New, Large Nonroad Spark-Ignition
Engines.
EPA regulations are subject to change after
publication of a Notice of Proposed Rulemaking
in the Federal Register. Usually a 90-day
period for public comments is required before
the proposed regulations are adopted. A
compliance date is set after a Final Rule Notice
is published in a subsequent Federal Register.
An issue of the Federal Register is
published each weekday except for
federal government holidays. The most
recent EPA regulatory change related
to propane-fuel stationary engines was
published as a Final Rule in the January
18, 2008 issue. Those rule changes
became effective March 18, 2008.
25
3.0
State governments whose air quality compliance program plans have been reviewed and
approved by EPA also can create and enforce stationary engine air emissions regulations.
The California Air Resources Board is a leading state agency whose air quality standards and
enforcement actions impact stationary engine emissions and hazardous air pollution limits.
in 40 CFR §60.4248 that should be understood by technicians servicing stationary engines
Stoichiometric means the theoretical air-to-fuel ratio required for
complete combustion.
Rich-burn engine means any four-stroke spark-ignited engine where the
manufacturer’s recommended operating air/fuel ratio divided by the stoichiometric air/
fuel ratio at full load conditions is less than or equal to 1.1.
Lean-burn engine means any two-stroke or four-stroke spark-ignited engine that does
IDENTIFYING THE IDEAL COMBUSTION AIR-TO-PROPANE
RATIO FOR SPARK-IGNITED INTERNAL COMBUSTION ENGINES
Identifying the meaning
of the terms “stoichiometric
combustion,” “lean,”
and “rich”
Stoichiometric combustion of a fuel would
result in complete burning of the fuel.
In the case of propane, which is made up of
hydrogen and carbon, complete combustion
would produce only carbon dioxide, water, and
minute quantities of oxides of nitrogen, the
predominant constituent of air besides oxygen.
Before exhaust emissions were a concern,
stationary propane and natural gas engines were
designed to run with excess air. These engines
ran very well with 5% to 20% excess air.
26
Excess air ratio is referred to as Lambda (λ). Stoichiometric air-fuel ratio is 1.0 (the blue line)
lean-burn operation is any ratio to the right of the stoichiometric point. (For EPA regulatory
purposes, a “lean-burn” engine is one with a λ ratio greater than or equal to 1.1.)
The air-fuel ratio would often vary with load, and as long as the engines would carry the load
Typically, carbon monoxide (CO) output is highest when an engine is running rich.
Hydrocarbon (HC) emissions, which represent unburned fuel, are highest when an engine
is running rich and lowest at stoichiometric, but will increase again when running lean due
to incomplete combustion. Oxides of nitrogen (NOx) are lowest when running rich, due to
the lower percentage of air to fuel, and highest when slightly lean of stoichiometric. NOx will
decrease at further lean mixtures due to reduced combustion temperatures. Carbon dioxide
(CO2) is typically highest at stoichiometric and is generally considered a measure of ideal
combustion. Oxygen (O2) is lowest when running rich and highest when running lean.
As exhaust emissions and reducing hazardous air pollutants became increasingly important,
it was discovered that these engines were running with very high NOx levels, sometimes at
the peak of the NOx curve. Two strategies evolved to reduce the NOx while limiting the carbon
monoxide (CO) and unburned hydrocarbons (HC).
lean-burn combustion.
1. Rich-Burn Combustion –
the engines at a stoichiometric fuel mixture. A stoichiometric mixture is the chemically
correct fuel mixture for combustion, with near zero oxygen left over in the exhaust. This
method of operation is suitable for a three-way catalytic converter. The mixture must be
precisely controlled in order for the reaction in a catalytic converter to oxidize the CO to
CO2 and reduce the NO and NO2 to N2 and O2 and not have undesirable products left over.
a. Rich-Burn Oxygen Sensor – In order to achieve the precision in the control of the
mixture required for the catalyst, an O2 sensor is placed in the exhaust before the catalytic
converter. The output of the O2 sensor is fed back to the control device to close the loop
on the amount of oxygen in the exhaust. The mixture is controlled to maintain very low
oxygen content, less than 0.02 percent in the exhaust, as indicated by the voltage
produced by the O2 sensor. This indicates that the combustion process is consuming
nearly all of the oxygen. If higher oxygen content is indicated, the engine is running too
lean. If lower oxygen content is indicated, the mixture is too rich.
27
3.0
The ideal switch point is determined by the design of the O2 sensor, but typically, 0.5
volts (500mv) is ideal. Oxygen sensors are available to meet a variety of engine
applications, and therefore may have different switch points, but rarely are their switch
points lower than 0.45 volts (450mv) or greater than 0.5 volts.
Wide-band O2
ranges may be experienced. Where traditional automotive engine O2 sensors produce a
rough “rich-lean” signal output, the wide-band O2 sensor produces a true signal showing
the actual air-fuel ratio. These two types of sensors are NOT interchangeable.
b. Characteristics of Rich Burn –
mode with a catalytic converter is they operate with very small quantities of NOx and CO
in the exhaust. At the discharge of the catalytic converter, NOx in the range of a few parts
per million is achievable.
A two-way exhaust catalyst converts HC and CO into CO2 and H2O.
A three-way exhaust catalyst is used where NOx
converted into CO2 and H2O. An engine using an exhaust catalyst should use electronic
fuel-mixture controls to keep the catalyst operating in its optimal range for catalytic
fuel mixtures can vary outside of the desired range of the catalyst due to component age
In general terms, gaseous-fueled engines may run hotter when running rich rather than
when running lean because no liquid fuel is evaporating and producing a cooling effect
inside the combustion chamber. An engine running at stoichiometric to approximately
10% rich will produce more power. Conversely, an engine running leaner than
stoichiometric will improve economy but produce less power.
2. Lean-Burn Combustion – The second strategy for reducing emissions is to run the
combustion process must be controlled within a narrow operating window. Charge air
temperatures and volume, together with air-to-fuel ratio and other operating conditions,
must be constantly monitored. The microprocessor-based engine controller regulates the
Many engines running in excess lean-burn mode utilize a turbocharger to bring the engine
power back to normal levels.
28
a. Lean-Burn Oxygen Sensor – The oxygen sensors used for lean-burn engines, unlike
the sensors used with rich burn, indicate a very wide range of oxygen in the exhaust.
These sensors are often referred to as lambda sensors, where lambda is the air-fuel ratio
that the engine is running at divided by the stoichiometric air-fuel ratio. Most engines
running in lean-burn mode use a wide-band O2 sensor because the traditional O2 sensor
b.
Engines running in the lean-burn mode offer several
important advantages including lower combustion temperatures, reduced emissions, and
decreased fuel consumption.
Identifying the ideal mixture of propane-air ratios that tend to
yield the lowest exhaust quantities of carbon monoxide and
oxides of nitrogen
The chart illustrates that, as a propane-air mixture goes from rich to lean, the emissions that
EPA regulations seek to control are reduced. Although unburned hydrocarbons (HC) initially
peak up, they are reduced. NOx, CO2, and CO all are trending down on the chart as the engine
is moved to the lean-burn side.
29
3.0
IDENTIFYING THE GENERAL OPERATING CHARACTERISTICS
OF AN ELECTRONIC EMISSION CONTROL SYSTEM
Identifying the typical components used in an emissions
control system and their functions
Electronic controls are made up of at least three items.
1. The fuel-control valve may be a stand-alone device or incorporated into other
components, including the carburetor or mixer assembly, and the vaporizer. The fuela. A pulse width solenoid that modulates air-valve vacuum, which alters the air-fuel ratio
by changing the vaporizer outlet pressures.
b. An electrical or pneumatically actuated valve mounted in the vapor or dry gas hose
between the vaporizer and the mixer body.
c. An internally mounted valve in a fully self-contained fuel carburetor assembly. This
device may operate by varying the size of the fuel outlet port through the use of a
an adjustable internally mounted regulator.
2. The control module may be a stand-alone device or incorporated into other components,
including the carburetor or mixer assembly or the vaporizer. Most modules control only
air-fuel mixtures.
3. The wiring, including the fuel-control switch.
Oxygen sensor — the primary emission
control system sensor, which is installed
in the exhaust system between the engine
RPM reference sensor — typically
magneto, or injector pump location.
Manifold air temperature sensor —
detects air density. Colder air is denser than
warmer air and may contain more oxygen by
volume.
30
Coolant temperature sensor — Measuring engine operating temperature is critical to
delivering the proper air-fuel mixture. Cold engines typically require a slightly richer airfuel mixture than engines that have reached the proper operating temperature. Gaseousfuel engines are not severely affected by rich fuel mixtures when cold, since the fuel is
already vaporized.
IDENTIFYING THE TERMINOLOGY USED TO DESCRIBE THE
OPERATING MODES OF THE EMISSION CONTROL SYSTEM
Open Loop Operation
1. On engines not equipped with electronic microprocessor fuel-air mixture and emissions
controls.
2. On engines equipped with electronic microprocessor control systems during the
period when the engine is started but has not yet reached operating temperature.
At such times the engine requires a richer propane-air cranking mixture, and some
of the sensors are temporarily not used to monitor exhaust gas, air density, and
other operating conditions.
Engines typically transition from open to closed loop at an operating temperature that is
pre-determined by the fuel system manufacturer. Some systems use the engine coolant
temperature sensor, while others use the oxygen sensor.
The average transition from open to closed loop will usually occur at around 160°F engine
coolant temperature. If the O2 sensor has reached the proper operating temperature
(generally at or around 600°F), or a voltage signal has transitioned from lean to rich,
crossing the center switch point, the system may have enough information to initiate the
transition. Some fuel systems may include a timer to ensure that enough time has passed
Closed Loop Operation
In closed loop operation, engine fuel-air mixtures, cylinder charging, and spark timing are
typically varied in response to exhaust gas sensor and other sensor outputs, as they are read
and interpreted by one or more microprocessors (electronic computers).
Simple closed loop fuel control systems may use as few as two inputs:
Ignition on.
O2 sensor.
31
3.0
More common systems will use:
Ignition on.
O2 sensor.
RPM reference.
More advanced systems will use:
Ignition on.
O2 sensor (either a rich-lean sensor or a wide-band Lambda sensor).
RPM reference.
Battery feed.
Manifold air pressure (MAP).
Throttle position (TPS).
Engine coolant temperature sensor (CTS).
The most advanced fuel systems use all or most of the following:
Ignition on.
O2 sensor (either a rich-lean sensor or a wide-band lambda sensor).
RPM reference.
Battery feed.
Manifold air pressure (MAP).
Throttle position (TPS, typically with drive-by-wire throttle control, integrated
into the governor).
Engine coolant temperature sensor (CTS).
Air temperature.
Fuel temperature.
Fuel pressure.
More precise control of the air-fuel mixture is possible when the processor can receive more
information (inputs) resulting in more accurate outputs to manage the combustion process.
Closed loop output fuel controls may be simple vacuum solenoids that pulse vacuum to the
engine. Other controls use an electric or vacuum-operated valve, which mounts in the pipe
changing the volume of propane and the vacuum signal seen between the regulator/vaporizer
and the engine/mixer.
32
Emission Control System Components Illustrated
The numbered components on the picture above are:
No.
Component
Function
1.
Mixer assembly (Woodward, N-CA200)
2.
Vaporizer (Woodward N-H420;
closely resembles the IMPCO Model L)
Converts liquid propane to vapor and reduces
container pressure to low pressure (negative)
3.
Fuel lock-off (AFC 121 or AFC 123,
Woodward #N3-0165-2)
not running
4.
Fuel control solenoid
Varies fuel supply to mixer in response to O2
sensor input to the control module
5.
Ignition coil
Provides proper voltage to spark plugs
6.
Control module
Converts O2 sensor and other inputs to fuel system
operating commands
7.
Engine RPM reference for the Murphy® panel
Monitors engine and provides engine over rpm
protection; may also provide input to control module
Not shown is the O2 sensor connection. Typically, the O2 sensor is close to the junction of the
left and right bank exhaust headers, or on one exhaust manifold. Some newer engines that
use an exhaust catalyst may use two or more O2 sensors. The primary sensor determines the
exhaust composition and sends information back to the fuel control module; the secondary
the catalyst is working properly. If the secondary sensor produces an output signal that closely
follows the primary sensor, the exhaust catalyst is not working.
33
3.0
Engines may also use three or four sensors. These are called Bank sensors, where Bank 1 is the
cylinder bank where the #1 cylinder is located and Bank 2 is the opposite bank. For example,
2 sensor in the cylinder bank where
sensor in the opposite bank, and B2S2 indicates the rear sensor in that bank. Although this
technology has been used mostly in over-the-road applications, there is a trend to adapt it for
off-road engines, especially where air quality is monitored.
The numbered components on the picture above are:
No.
Component
Function
1.
Original crankshaft position sensor
2.
Engine RPM reference for the Murphy panel
Monitors engine and provides engine over rpm
protection; may also provide input to control module
3.
Ignition module
Provides ignition timing to DIS coils
4.
O2 sensor
Monitors O2 in exhaust gases, inputting to air-fuel
control processor built into component number 5
5.
Unitized carburetor, pressure regulator,
air-fuel mixer
Provides air-fuel management system responding to
the O2 sensor inputs
6.
May be called “Coil-On-Plug” or “Coil-Over-Plug”
Distributorless Ignition System (DIS)
Provides ignition voltage to spark plugs
Provides ignition timing inputs
®
The Continental Controls system illustrated on the previous page is fully self-contained,
relying on inputs from the engine RPM and O2 sensors. Once the system is installed and
the initial setup is completed, the unit requires no further calibration. Setup requires a
proprietary computer program and the appropriate calibration tables for that particular
engine series (engine family). These values are not user-adjustable.
34
3.0
Lab Activity
Identify the Components of an Emissions Control
System and Each Component’s Function
Directions: Complete each task to demonstrate your ability to identify
components of a propane-fueled engine emission system.
1. Fill in the numbered blanks below the picture to identify each numbered component and
emission control and the component’s function.
Component
Function
1
2
3
4
5
6
7
35
3.0
2. Fill in the numbered blanks below the picture to identify each numbered component and
emission control and the component’s function.
Component
1
2
3
4
5
6
36
Function
4.0
Propane-Fueled
Engine Fuel System
Maintenance and Repair
37
4.0
INTRODUCTION
While maintaining propane-fueled engines, technicians often use the same patterns of
inspection, testing, and troubleshooting they use on any other engine type. Many times the only
difference in diagnosing propane fuel-system problems versus other fuel-systems centers on
the mechanical operation of the propane fuel system components and checking for abnormal
conditions within the pressure-regulating and fuel-to-air metering components of the system.
4.1 Identify basic diagnostic tools needed for determining proper operating condition of
propane engine fuel-system components.
4.2 Identify a preliminary list of abnormal operating conditions for an engine that are not
caused by the propane fuel system.
4.3 Identify a preliminary list of propane fuel-system inspection points to check before
disassembling any fuel-system component.
4.4 Perform inspections and tests to determine the operating condition of propane fuelsystem components.
4.5 Perform maintenance operations on propane fuel-system components.
4.6 Identify inspection and testing procedures to determine proper operating condition of
emission control systems.
IDENTIFYING BASIC DIAGNOSTIC TOOLS NEEDED FOR
DETERMINING PROPER OPERATING CONDITION OF
PROPANE ENGINE FUEL-SYSTEM COMPONENTS
Early internal combustion engine technology was easy to understand for most service
technicians because it used mechanical devices to control combustion. Whether the engine
used spark ignition (gasoline or gaseous fuels like propane) or compression ignition (diesel),
Fuel and air mixture.
Spark (or compression).
Timing (spark and dwell for gas, or fuel injection for diesel).
These criteria for proper engine operation continue to apply. Current and future efforts to
Electronic sensors and controls (to more precisely regulate fuel and air mix, ignition, and
combustion timing).
38
Propane-Fueled Engine Fuel System Maintenance and Repair
To determine the operating condition of propane engine fuel components and to diagnose
problems, service technicians should have test equipment to measure each of the four areas
and recommendations should guide in the selection of diagnostic tools and test equipment.
a.
b.
c.
d.
0–5 psi.
0–15 psi.
0–30 psi.
0–200 (or 0-300) psi.
A water column manometer capable of reading positive and negative pressures from 0-12
inches water column.
1/4- and 1/8-inch NPT test tap adapters for use with test gauges and water column
manometer hoses.
A digital volt and ohm meter (DVOM) — A DVOM with resolution in the 0 to 1000mv and
0 to 20 VDC range with averaging functions is recommended.
For example, IMPCO recommends technicians servicing its fuel
system components to have the IMPCO ITK-1 test kit designed
for testing and troubleshooting IMPCO gaseous fuel systems.
0–200 PSI gauge – For measuring fuel container
pressure or (on dual fuel systems) to measure gasoline
fuel system pressure.
0–5 PSI Gauge – For measuring IMPCO pressure
regulator, primary pressure.
0–10" H2O column gauge – For measuring
IMPCO pressure regulator, secondary pressure.
G2–2 lever gauge – For correct adjustment of
the IMPCO pressure regulator, secondary lever.
Gas Exhaust Gas Analyzer
analyzer (such as the Infrared Industries FGA-5000).
39
4.0
IDENTIFYING A PRELIMINARY CHECKLIST OF ABNORMAL
OPERATING CONDITIONS NOT CAUSED BY THE PROPANE
FUEL SYSTEM
Inoperative or defective engine safety switch.
a. Engine oil low-pressure interlock.
b. Low fuel-pressure interlock.
c. Low coolant interlock.
d.
Fault in ignition system.
a. Battery, alternator, or wiring fault.
b. Improper spark plug wire routing to spark plug(s).
c. Disconnected, damaged, or grounded spark plug wire.
e. Damaged or inoperative primary section of the ignition system (points, condenser,
ignition module, Hall Effect switch, pickup coil).
f. Damaged or inoperative secondary or high-voltage section of system (coil outage).
g. Damaged, improperly gapped, or improper spark plug type.
Spark timing fault indicator.
Inoperative mechanical or electric engine speed control.
Disconnected, damaged, or leaking vacuum hose or connection.
Disconnected or damaged sensor or control wiring cannon plug or terminal connector.
a.
b.
c.
d.
Head gasket failure.
Improperly installed or failed timing chain.
Excessive engine wear.
Low or erratic compression.
Erratic engine operation or complete
a. Wiring problems in the safety control
panel box.
b. Weak signal from a sensor such as
an oil level, oil pressure, coolant
temperature, or rpm sensor.
Making it a habit to always check the
“Murphy®” switches and their wiring
should be an early step in your
diagnostic routine.
40
For example, the picture to the right was
taken of an irrigation engine reported
by the customer to have a propane fuelrelated fault. Upon further investigation,
the engine’s safety system switch wiring
caused erratic operation of the engine.
The white wire was gnawed through,
but intermittently completed a control
circuit. A ground wire also was found to
be stripped of insulation.
It’s important to check for electrical
control problems, low lubrication, or low
coolant levels before taking on the fuel
system or ignition systems.
IDENTIFYING A PRELIMINARY CHECKLIST OF PROPANE
FUEL-SYSTEM INSPECTION POINTS TO CHECK BEFORE
DISASSEMBLING ANY FUEL-SYSTEM COMPONENT
Out of fuel or low fuel condition in supply tank.
Inadequate vaporization capacity of storage container or converter/vaporizer as indicated
by frosting, low fuel inlet pressure, or low coolant level.
Coolant leakage at converter.
Inoperative fuel lock-off.
Rough engine operation at idle or no response to increased throttling.
Seized air valve in air-valve-equipped mixer.
Seized throttle control shaft.
NOTE:
Whenever you perform a stationary engine service operation,
1. You read and apply OEM operating and troubleshooting instructions
and follow the procedures given in them.
2. You comply with all applicable engine emissions regulations
and requirements.
41
4.0
PERFORM INSPECTIONS AND TESTS TO DETERMINE
THE OPERATING CONDITION OF PROPANE FUEL-SYSTEM
COMPONENTS
Take these steps before proceeding with disassembly, internal
1. Shut off the propane at the supply tank and at any line valve(s).
2. Safely vent the propane to an area free of ignition sources.
Internal component pressure must be reduced to atmospheric
pressure.
Inspecting and Testing To Determine the Operating Condition
of Propane Fuel Lock-offs
Vacuum Lock-offs
First, check for a broken
or missing vacuum line or
connection. Typically they
are designed to operate
with 0.2 inches water
column opening vacuum
(mixer air-valve vacuum
only). This vacuum is
stable between 4 and 8
inches of negative water
column pressure under
almost all engine operating conditions.
a.
oil-soaked, or otherwise damaged.
b. With the engine operating under load, inspect the lock-off. If the lock-off body is cold,
42
Replacement
a.
a compressed cotton pad; its
ten micron range.
b.
any debris found.
Vacuum Operated Fuel Filter/Lock-off Cutaway View
c. If the debris is a reddish powder, it
will usually cure this problem.
d. If the debris is a gray powder, the material may be metallic particles from the propane
marketer’s delivery vehicles or bulk plant.
e. If the debris is black (the most common debris seen), it is typically excess carbon from
the fuel tank. Much of this carbon is created during the tank manufacturing process
and may also be called “milling” or “rolling” scale.
f. If the debris is black but crumbles easily, it might indicate rubber hose deterioration
engine and tank are located).
Testing the Vacuum Diaphragm
a. Apply light vacuum to the vacuum port. The vacuum should hold steady. The
diaphragm should move to the open position at approximately –0.2 inches water
column. This test will verify a problem with the vacuum supply, hose, or diaphragm.
b. If you cannot apply vacuum to the port, you may insert a suitable probe (for example,
a clean piece of welding rod) into the vent hole in the back side of the vacuum lockoff and depress approximately 3/4 of an inch. If pressurized air (connected in place
probably ruptured.
c. If pressurized air comes out of the vacuum port, the stem of the lip seal in the LP outlet
is extremely worn, the body may be worn past service limits, requiring replacement of
the complete unit. If this is the problem, the engine will exhibit excessive idle and low
air-fuel mixture.
43
4.0
Electric Lock-offs
An electric lock-off is a magnetic coil
(solenoid). When energized, the coil
becomes an electromagnet that moves a
When the electrical current stops, the
magnetic force acting on the piston ceases,
and a spring forces the piston back down
Electric lock-offs are widely used in
Two Styles of Electric Lock-offs
automotive applications, especially on
dual-fuel systems in pickups and on
industrial lift trucks. They are not commonly found on stationary industrial engines, where
vacuum lock-offs are typical.
Electrical lock-offs are not polarity sensitive. Some are internally grounded, while others are
grounded with a second electrical lead. If the lock-off is internally grounded, the technician
should verify that the attached components are grounded to the chassis or support structure.
Filter Replacement
a.
off shown above on the left is a
looks like a small ball of yarn.
b.
separate from the lock-off is used
with the lock-off style shown above
in the picture to the right, resemble the
c.
44
Testing an Electric Lock-off
a. With the engine shut down, use a 12-volt supply to verify operation. Energize the
lock-off with a jumper wire from the battery or other 12-volt source. An audible “click”
should be heard. If no sound is present, check the solenoid ground.
b. Verify that all wiring connections are either soldered and heat-shrink-tubing wrapped,
or are well-sealed automotive type (cannon plug or boot) connectors. Piercing-type or
twisted wire and wire nut connections are not recommended. If present, these types of
connections should be replaced to assure reliable operation.
Electric Lock-off Maintenance/Repair
a. If the electric lock-off does not work properly with the engine shut down and when
energized by a known 12-volt source, replace the unit.
b. If the electric lock-off works properly with the engine shut down and when energized
actual current source (for example, an oil pressure sensor) should be checked for
c. Most electrical lock-offs are designed to operate with the coil in a vertical orientation
(with the coil on top). This is to ensure that the internal pilot piston does not become
immobile due to accumulation of “heavy ends.” Propane contains trace amounts of
components such as propylene that when heated above 160°F may condense out in a
In-Line Cartridge Filter Maintenance
a. Used in the vapor line to catch
any pipe scale or small particles,
b.
1. After the run-in period, a few
operating hours after the system is
placed into service.
2. After replacing the propane tank
and/or connecting piping.
3. According to a periodic
maintenance program.
In-Line Cartridge Filter Installed Below
(Upstream of) the Second-Stage Regulator
45
4.0
Inspecting and Testing
to Determine the Operating
Condition of Propane Fuel
Pressure Regulators
Pressure regulators used with propane
vapor-fueled engines should be selected and
installed according to the engine and regulator
manufacturers’ instructions.
First-Stage Regulator (Typically Red Colored)
at the supply tank reduces vapor pressure from
variable tank pressure to a stable pressure of
10-psig or less. These regulators are usually painted
plugged test ports for verifying output pressure
using a test gauge.
A second-stage regulator may be installed outdoors
at the engine. These regulators are typically painted
gray, brown, or green by the manufacturer. Pressure
output from the second-stage regulator is typically
6 to 8 inches water column. Verify that the secondengine fuel load.
Second-Stage Regulator
(Typically Tan, Gray, or Green)
For pressure stability to the propane-air mixer,
immediately upstream of the mixer.
Final Stage In-Line Regulator
46
Regulator Inspection: First and Second Stage Regulators
a. First- and second-stage regulators are provided with a vent to allow air movement in
and out of the area above their diaphragms and to vent propane vapor from an internal
the regulator from closing (“locking up”) when there is no downstream demand.
b. They must be installed with the vent pointing down, or otherwise protected under a
dome or other structure to prevent vent blockage due to snow, ice, or other debris.
c. An insect screen should be in place at the regulator vent, and the adjusting screw cap
should be in place to seal the regulator body.
d. Regulator installations should comply with the manufacturer’s instructions and NFPA 58.
Courtesy of Sherwood LPG Products
Inspecting and Testing to
Determine the Operating Condition
of Fuel Converter (Vaporizer)
One of the most important diagnostic steps in an engine
no-start, hard-start, or slow-start condition is to test
vaporizer pressures.
Excessively high primary pressure will prevent the fuelmixture controller from maintaining proper air-fuel ratios.
High or low secondary pressure will result in poor control of
other operating problems.
Pressure Testing Procedure for IMPCO and
Woodward Vaporizers
With the engine shut down
1. Remove the 1/8-inch test port plug in the low-pressure section and install a pressure
gauge or manometer marked in inches of water column.
47
4.0
2. Remove the 1/8-inch test port plug in the high-pressure section and install a 0- to 15-psig
pressure gauge.
3.
a. High-pressure readings should be no more than 5 psig with engine off, and no more
than in the 1.5- to 3.5-psig range with the engine running.
b. Low-pressure readings should be in the –0.5 to –3.5 inches water column range with
the engine running.
Inspecting and Testing To Determine the Operating Condition
of the Propane-Air Mixer and Throttle Body
To this point in the discussion of fundamental evaluation of fuel-system components,
one or more relatively simple measurements give an indication of proper component
operation. Inspecting and testing propane-air mixers and throttle bodies call for applying the
troubleshooting procedures given in the OEM instructions for the engine and for the OEM
Equipment manufacturers specify different procedures for determining the operating condition
of the mixer and throttle body that make up a propane carburetor for a small stationary engine
driving an electrical generator, versus a large engine driving an irrigation pump.
Correct measurements of engine exhaust gases must also be made at prescribed operating
conditions from idle to fully loaded before adjustments or repairs can be made. Prior to making
these exacting measurements, or performing maintenance on propane carburetors, be certain that
all upstream fuel-system components and emission controls are apparently operating properly.
PERFORM MAINTENANCE/REPAIR OPERATIONS ON
PROPANE FUEL-SYSTEM
COMPONENTS
Perform Maintenance
Operations on Propane Fuel
Lock-Offs and Fuel Filters
Inspection of fuel lock-offs and associated
completed at each service interval set out in
the OEM operating instructions. A periodic
maintenance schedule for irrigation engines is
located in Appendix B to this training guide.
“Trap-it”-Type Fuel Filter
according to the manufacturer’s
48
Adjust Propane Fuel-Pressure Regulators to Proper Output
Setting If Appropriate
These are types of regulators a turbocharged
irrigation engine supplied vapor from a
supply tank.
A second-stage regulator located at the
engine fuel piping riser.
An in-line regulator which may be a direct
operating regulator, or may function as a
pilot (or “sub-regulator’) connected to the
second-stage (“main regulator”).
Cut-away View of a “Sub-Regulator”
Courtesy of IMPCO Technologies, Inc.
Diagram of Carburetor, Air/Fuel Ratio Controller, Pilot Regulator, and Main Regulator
Diagram Courtesy of IMPCO Technologies, Inc.
A pilot regulator (sometimes called a “sub-regulator”) is often used with a turbocharged
engine to give quicker response to pressure change when the engine rpm is varied from idle
to full load.
regulator. Verifying proper pressure output setting of the second-stage and any connected
sub-regulator may be necessary if engine performance is not as it should be, or if a regulator
is replaced.
49
4.0
OEM instructions for adjusting pilot
and main regulator output pressures
must be strictly followed to obtain
proper operating fuel supply to the
engine, especially an engine equipped
with a turbocharger.
Improper regulator output settings
may result in poor engine performance,
that do not comply with clean air
regulations.
Manufacturer’s Diagram of Pressure Measurements Needed for
Adjustment of Sub-Regulator and Main Regulator
Diagram Courtesy of IMPCO Technologies, Inc.
Perform Maintenance and/or Repair Operations on Fuel
Converter (Vaporizer/Pressure Regulator)
If testing or inspection of a propane converter (vaporizer/pressure regulator) is required, obtain
the appropriate manufacturer’s repair parts kit, and follow the manufacturer’s instructions.
Phillips #2 screwdriver (some models)
Appropriately sized male Torx screwdriver (Most, but not all, models manufactured after
1996 were equipped with Torx drive screws.)
Pair of needle-nose pliers
G2-2 lever height measurement tool (may be supplied in overhaul kit)
NOTE:
pressure in the fuel system. Remove the vaporizer from the engine and
clean off any oil or dirt accumulation. Place the unit on a work bench or
clean work area.
50
Using an IMPCO model E as an example, the basic
1. Remove the eight top cover screws. Remove the
cover and set it aside.
IMPCO Model E Cover
2. Remove the secondary diaphragm and inspect
for damage. (Note if any oil has collected in the
vaporizer body.)
3. Use a soft, clean towel or shop cloth to remove
any debris from the diaphragm. (DO NOT use
carburetor spray cleaner on any diaphragm or
seat material.)
4. If any perforation, tear, layer separation, or
other damage is seen on the diaphragm, replace
it with a new diaphragm (provided in the rebuild
parts kit).
5. Inspect the vaporizer body for oil and debris.
Using a soft, clean towel or shop cloth, remove
any oil or debris.
Inspect the diaphragm
for damage.
Note any oil pooling.
.
51
4.0
6. Remove the secondary lever fulcrum pin by
the right, and the retaining pin only, setting the
retaining pin aside for inspection.
Remove this screw.
Remove this pin.
7. Inspect the green secondary fuel seat for severe
imprint, tears, cuts, perforation, and a concentric
imprint pattern. Inspect the metal fuel outlet for
a sharp edge, cuts, nicks, or concentric shape. If
the edge is sharp use 220-grit abrasive paper and
lightly polish the outlet to remove the edge.
Inspect these areas
for damage.
8. Next, remove the primary plate.
a.
shown, leaving two in place.
b. While holding the plate down
(it’s spring-loaded), remove
the two remaining screws.
The plate will retain the
primary pressure diaphragm
and two springs.
a.
b.
9. Carefully remove the primary cover. Inspect the springs for damage; then place them in a
secure location. Do not modify the spring tension.
52
10. Remove the primary diaphragm and primary
seat actuating pin.
a. Carefully remove the diaphragm. If
the diaphragm shows any signs of oil
contamination, swelling, or torn edges,
it MUST be replaced.
a.
Carefully remove
the diaphragm.
b.
Now remove the
primary pin.
c.
Remove these two
remaining screws.
b. Remove the small pin located under
the small extension of the primary
diaphragm.
c. Remove the two remaining screws to
the lower body that retain the vapor
chamber.
d. Separate the two halves and discard the
rubber gasket.
11. Inspect the yellow sponge (used only on the
model E vaporizer). The sponge absorbs any
liquid propane, giving it a chance to vaporize
before entering the engine.
The yellow sponge
absorbs liquid fuel
until it vaporizes.
53
4.0
12. Inspect the primary seat.
a. Remove the primary inlet seat and
spring. Inspect the rubberized surface for
tears, perforation, excessive hardness, or
a gum-like consistency (indications that
replacement is necessary). The primary
seat is the component of the vaporizer
most subject to “wear and tear” failure.
b.
for sharp corners that contribute to
binding and hanging in the open position.
c. Inspect the fuel inlet for damage
including cracks, looseness, corrosion,
or concentric surface.
a.
Inspect the rubber
surface for damage.
b.
c.
Inspect the fuel
inlet for damage.
13. Inspect the vaporizer body.
a. Inspect the vaporizer body dividers and
channels for corrosion, cuts, and cracks.
a.
High pressure tap.
Coolant drain.
Inspect rows for
corrosion or damage.
54
b. Turn the body over and remove the six
remaining screws. Separate the two
metal body pieces and remove the rubber
gasket/insulator.
b.
Remove the screws.
c.
Inspect for corrosion
or damage.
c. Inspect the lower plate for corrosion
or damage. The outer circumference is
especially susceptible to corrosion when
an improper coolant mixture is used.
If any corrosion is present along the
edge, the body must be surface-ground
to return the gasket sealing surface to a
Reassembly
14. Reassemble the lower coolant chamber, replacing the rubber gasket/insulator. Tighten the
screws screwdriver-tight (approximately 50 inch-pounds). Do not over-tighten the screws.
15. Reassemble the lower body and sponge.
a. Install the new primary spring/seat
and new sponge.
a.
Inspect new primary
seat and sponge.
55
4.0
b. Place the vapor chamber with a new
start two screws. Do not tighten the screws
at this time.
b.
c. Assemble the primary plate by placing
the primary actuating pin in the hole.
Place the primary diaphragm over
the four line-up pins.
Place the two springs over the
diaphragm.
Place the cover over the two springs,
then press fully down.
Hold the cover down with one hand
and start the two pan-head screws.
Tighten those two screws.
Start the remaining screws but do not
tighten them until the diaphragm is
visible around the perimeter of the
primary diaphragm plate.
16. Install the secondary valve pin and
fulcrum assembly.
a. Insert the pin.
b. Install the remaining screw.
c. Tighten all screws to approximately
50 inch-pounds (screwdriver tight).
d. Insert the secondary balance spring
(either blue or orange colored,
depending on pressure requirements).
56
Finger-tighten
these two screws.
Use your thumb to hold
the plate down.
Install these
c.
Insert pin, then install
screw. Tighten screws.
17. Set the lever height.
a. Install the G2-2 gauge and set the lever
height by placing the tool across the top
surface of the vaporizer body. The latch
is required to hook the latch pin, or if the
latch pin raises the gauging tool, adjust the
lever by bending it at the fulcrum point.
b. If the gauging tool is not available,
set the latch pin height to no more than
0.125" below the top surface of the
vapor chamber.
Use G2-2 gauge and
test lever height.
Complete the converter reassembly by performing the previous steps in
reverse order.
57
4.0
Perform Maintenance and/or Repair Operations on
Propane-Air Mixer
IMPCO Technologies Propane-Air Mixer
Continental Controls Corp. Propane-Air Mixer
When service is performed on propane-air mixers and carburetor systems, the following
information must be remembered and applied.
Highest
Fuel Btu Content
Lowest
The body of a mixer may be the same for any of these gases, but internal components will
differ. For example, gas valves, diaphragms, air valves, and gas inlet bodies and adjusting
components must be selected for the gas application.
Throttle bodies will have different bore diameters for the gas application.
Component options for stoichiometric or lean-burn gas valves by gas type must be
matched to the engine application.
When a mixer, mixer component, or throttle body is repaired or replaced, engine exhaust
gases must be analyzed, and the repaired/replaced unit must be adjusted to obtain
the best settings for engine performance, fuel economy, and emissions that meet the
In general terms, when a propane-air mixer is adjusted in open loop operation at full power (engine
Power.
Fuel economy.
Emissions.
58
Servicing Propane-Air Mixers
assembly.” The section of the assembly upstream of the throttle body mixes air and propane
for combustion in the engine cylinders and is called a mixer. In this discussion of propaneair mixer maintenance, an IMPCO Technologies model 425 is used to illustrate steps in
teardown, inspection, and installation of a repair kit.
All IMPCO 425 propane mixers utilize a “fuel on demand” operating method, meaning that
fuel is pulled in by demand, NOT blown in or supplied to the mixer under pressure. The fuel
is supplied from the source through at least one and up to three pressure regulators. Typical
fuel inlet “pressure” is from –.5 to –1.5 inches water column, negative pressure. Note that the
greater the negative pressure number, the greater the water column vacuum required to draw
the fuel in.
An IMPCO 425 air-fuel mixer is
typically robust and easy to service.
A single 425 carburetor assembly
can be used for a number of engine
applications, providing adequate
air and fuel for up to approximately
325 brake horsepower.
In normal use, the mixer assembly
will last many hundreds to thousands
of hours with little maintenance.
Idle Adjustment Side View
Fuel Inlet Side View
During normal propane fuel usage, light oil deposits may accumulate on the mixer’s internal
components. If not cleaned on a regular basis, these deposits may impede the movement of
the air valve or cause improper fuel metering. The following steps outline a typical teardown,
inspection, and reassembly process of an IMPCO 425, and will outline several areas that have
traditionally caused some in-service issues.
Installing a Propane-Air Mixer Repair Kit
The body assembly.
The body cover, also called a “lid.”
The air-gas valve assembly, which includes the valve, diaphragm, and reinforcing plate.
The air-gas spring.
The idle diaphragm cover, which includes the spring.
The idle diaphragm.
The idle diaphragm gasket.
59
4.0
The mixer may be disassembled on the engine, since there are few components that can
easily fall into the engine. During mixer service, the technician should cover the open mixer
assembly with a suitable cover.
It is recommended that the engine be decommissioned during mixer service. Remove the
engine start key, or prevent the engine from starting by some other means.
To disassemble, inspect, install replacement parts, and reassemble the mixer, you will need
A standard screwdriver.
Torx® screwdriver (for models that use Torx head screws).
A thin blade knife or putty knife.
A ruler.
Suitable cleaning solvent — do not use carburetor cleaner or immerse mixer components
in carburetor cleaners.
Clean, dry shop cloths.
Inspecting/Replacing the Air Valve
1. Remove the four screws located on the top lid.
Gently lift the lid off of the body assembly. It is
common for the air-valve diaphragm to stick to the
mixer lid. If it does, gently pry the diaphragm loose.
The diaphragm is spring loaded; be careful not to
lose the spring.
IMPCO Model 425 Top View
2. Examine the diaphragm and spring. Notice the
a. The yellow diaphragm material.
b. The silver decal.
The yellow diaphragm material is the premium
silicone.
60
3. If the diaphragm is cracked, torn, cut, or otherwise damaged, it should be replaced with
425. ” Add a “dash 2” (-2) to include the premium yellow diaphragm material for both the
neoprene, also called “Hydrin” diaphragms. In all cases, any mixer may be (or should be)
upgraded to “-2” quality during rebuild.
number. Individual letters and numbers in the air valve part number (AV1-1651-2) have
a.
b.
c.
4. The side view of the air-gas valve shows
machine any surface of the valve. If the valve
is dirty, use a suitable chemical cleaner that
will dissolve the accumulated oil and dirt.
Air Valve Side View
The bottom of the air-gas valve shows the fuel
metering cone. The general taper of the cone,
along with the grooves, controls the delivery
of fuel, depending on the amount of lift of the
valve assembly in response to engine vacuum.
Air Valve Bottom View
61
4.0
The #19 air-gas valve is the
standard valve used with noncomputer-controlled engines,
designed for stoichiometric
air-fuel mixtures.
The #44 air-gas valve is designed
for stoichiometric idle mixtures,
changing proportionally to
approximately 15 percent lean at
mid to wide open throttle.
The #51 air-gas valve is designed
for use with computer-controlled
engines. This valve is calibrated
for approximately 10 percent
excess fuel, relying on the
computer to command a lean
mixture through vacuum controls
at the vaporizer.
A comparison of the different gas valve shapes reveals that the narrowest valve allows the
most fuel to bypass, providing the richest fuel mixture. The thickest valve allows the least
amount of fuel to bypass, resulting in the leanest fuel mixture.
The shape of the taper also affects fuel-air mixture. If the valve taper is stepped, the valve may
Finally, the number and position of the notches machined into the sides of the gas valve
determine the overall fuel mixture. If the notches extend down to the cushion seal, a richer
mix is produced off of idle. Notches machined starting mid range down the taper will be richer
at that point.
Most IMPCO 425 mixers used in industrial applications are mounted vertically. Occasionally,
one may be mounted horizontally due to mounting logistics or other constraints. Horizontally
mounted mixers may exhibit accelerated wear in the air-gas valve guide area. The fuel
opening and valve guide bushing may become egg-shaped. If this is the case, the mixer cannot
be successfully re-used and must be replaced.
62
5. When inspecting the fuel delivery portion
of the air-gas valve and the mixer body,
check for any cuts or scratches on the
mixer’s fuel outlet opening. There are two
sealing surfaces in the mixer body. The
lower surface is the opening where fuel is
delivered against the tapered gas valve.
The upper surface is the guide for the
valve assembly.
Look for corresponding scratches on the Delrin© guide bushing on the air-gas valve.
Also inspect the black cushion seal at the base of the tapered gas valve where it attaches
to the assembly.
If the black cushion seal is damaged or missing, the engine will be hard to start and may
have severe low-speed fuel-mixture irregularities.
Place a clean air-valve assembly in the mixer body and slowly rotate. The air-gas valve
assembly should rotate smoothly without any noticeable resistance. If there are any tight
spots, check both the air-gas valve guide bushing and the mixer body for contamination,
cuts, scratches, or any polished spots, which may indicate excessive contact.
If the mixer body is excessively dirty, clean the mixer with a suitable cleaning solvent.
Reinstall the air-gas valve back into the mixer body with the valve portion wet with solvent.
Slowly rotate the air-gas valve assembly and lift throughout its travel to ensure that there is
no binding at any point.
63
4.0
Inspecting/Replacing the Idle Diaphragm and Seat Disc
The IMPCO 425 utilizes an idle diaphragm to control idle and low-speed fuel mixtures. This
diaphragm senses air-valve vacuum and allows fuel to bypass the air-valve metering portion
directly into the base of the mixer body.
1. Remove the four screws holding the
diaphragm cover.
Gently pry the cover from the mixer body.
2. Carefully remove the gasket using a thin blade
knife or scraper blade. It is common for the
gasket to tear. The gasket is usually NOT glued
to the diaphragm.
Carefully remove the diaphragm and inspect
for cracks or tears.
64
3. Carefully inspect the lever assembly for
installed or overtightened idle adjusting
screw can bend the lever.
Inspect the seat disc (bottom side of lever
pictured—on the right end). Inspect the
rubberized surface for tears, perforation,
excessive hardness, or a gum-like
consistency (indications that replacement
is necessary).
4. Inspect the cavity under the diaphragm
for accumulated dirt or heavy ends. Verify
a. The small hole at the lower/center of
the cavity must NOT be plugged.
b. The large hole directly above the
smaller one allows fuel into the air
plenum, into the gap between the
upper and lower fuel passage.
c. The opening at the right side is the
fuel supply.
Reassembly
To reassemble the IMPCO 425 air-fuel mixer assembly, reverse the steps listed for teardown,
installing replacement parts as needed.
1. Place the idle diaphragm over the four guides in the mixer body, followed by the gasket.
Ensure that the tapered balance spring is fully seated in the idle diaphragm cover (the
to hold the lever in the upward position when installing the cover. It may also help to back
the screw out four to six turns, and then return to the original position.
Tighten the four screws to approximately 25 inch/lbs. (light screwdriver torque).
65
4.0
2. For initial starting reference, the idle adjusting
screw may be set to 3/4 inch, measured from the
base of the plate to the top of the head.
3. Place the air-gas valve in the mixer body. Ensure
full movement (about 1/2 inch travel).
Verify that the diaphragm vacuum opening is
as shown in the image at right.
4. Reinstall the spring (do NOT modify the spring by increasing tension, clipping coils, or
adding shims). Basically, if the spring is weakened, the diaphragm will lift early and will
make the fuel mixture leaner, not richer. If the spring is strengthened by stretching or
shimming, the overall mixture will be richer, but not progressively. Any experimentation
should ALWAYS be accompanied by a means of returning the component back to its
original state.
5. Reinstall the top cover and tighten the screws to approximately 25 inch/lbs.
(screwdriver torque).
Whereas idle mixtures are adjusted at the idle screw, full-load fuel mixtures are adjusted
at the load screw, also called the “power valve.” Although opening the “power valve”
All mid-range fuel mixtures are managed by the shape of the gas valve, or electronic
engine control unit.
66
The base full-load fuel mixture may be
of the mixer to the top of the bolt head.
Note that these baseline measurements are for
initial fuel mixture settings and will probably
possible to get the engine running, the engine
testing is performed.
A stand-alone emission analyzer.
A closed-loop engine management
system with monitoring capabilities.
A wide-range oxygen sensor
(also called a wide-band, broad-band,
or Lambda sensor).
A standard oxygen sensor.
Adjusting the Engine Using a Four-Gas or Five-Gas
Emissions Analyzer
Start the engine and allow it to reach the operating temperature, usually a minimum of 160°F.
Engine Idle Adjustment
Follow the instructions on initializing the analyzer. Insert the exhaust gas probe into the
exhaust pipe opening. Adjust the CO for the lowest value, usually from 0.3 percent to 0.7
percent. Monitor the HC and O2 at the same time you are adjusting the CO. If the HCs begin
to climb while you are attempting to lower the CO, the engine is at its leanest condition. The
.
2
Try to balance the CO, HC, and O2 for their lowest values at the same time.
If the analyzer has a NOx function, adjust the engine for lowest NOx and let the other values
adjust where they will.
If the engine is equipped with a computer-controlled air-fuel ratio system, follow the
manufacturer’s recommendations for setting the mixture.
67
4.0
If the engine is equipped with a wide-band Lambda sensor, adjust the fuel mixture for
Lambda = 1 for stoichiometric, or by the manufacturer’s recommendations if the engine is a
lean-burn engine.
If the engine is equipped with a standard oxygen sensor, connect a digital volt-ohm meter to
the sensor output wire. Adjust the idle mixture for a sensor reading of approximately 0.450
volts (450 millivolts).
Adjustments at Rated Engine RPM and Load
running rich throughout the load range, it may have the incorrect air-gas valve. If it is running
at a normal air-fuel ratio at low to mid range but richer at full load, slowly turn the load screw
counterclockwise until the air-fuel ratio is stabilized. Attempt to reach the same exhaust
emission values at load as those that were seen at idle.
If possible, use a laser-type thermal sensor and monitor the exhaust manifold temperatures.
Exhaust temperatures should be recorded for future reference. Temperatures that are higher
than normal indicate a rich air-fuel ratio. This may also be accompanied by the exhaust
manifolds that have a red appearance (not red from engine radiant heat but from the metal
reacting to excessive heat and oxidization).
68
IDENTIFYING INSPECTION AND TESTING PROCEDURES TO
DETERMINE PROPER OPERATING CONDITION OF EMISSION
CONTROL SYSTEMS
Under closed-loop operating conditions, the
best combination of power, fuel economy,
and emissions can be obtained with the use of
computer software and programmable emissions
controls and air and fuel input controls.
To properly adjust propane-air mixtures, follow
following required items.
Emission gas analyzer.
Computer software.
Engine fuel and emission control equipment.
Adjusting Propane-Air for Best Operation
Exhaust Gas Analyzer and Laptop Computer Used to
Obtain Best Operating Adjustments for Power, Fuel
Economy, and Emissions
Closer View of Exhaust Gas Analyzer
69
4.0
analyzer shown to the right is a
compact exhaust gas measuring unit.
Accessories for the device include a
docking station with computer output
Courtesy of Bridge Analyzers, Inc.
Closing Comments
require fewer periodic adjustments than an engine operating on open loop. Some closed-loop
controllers are simple self-contained air-fuel controllers that require minimal engine inputs
and are easily installed, while others are full-authority engine management controllers.
The effective operation of these devices still relies upon a functioning engine and fuel system.
are the result of installing an engine that is not properly matched to the work load.
For a review of the sensor inputs and basic air-fuel controllers, please refer to chapter 3.
70
4.1
Lab Activity
Disassemble, Inspect, and
Perform Maintenance and/or Repairs on
Propane Fuel-System Components
Directions: Fill in the blanks provided to identify each item shown and how to
determine if a repair or replacement action is needed.
1. The component being removed from the converter is the __
_________________________________________
_________________________________________
It should be inspected for the presence of ____________
_________________________________________
_________________________________________
_________________________________________
_________________________________________
_________________________________________
2. The condition shown in the picture to the right indicates __
_________________________________________
_________________________________________
The action to take to restore proper operation is ________
_________________________________________
_________________________________________
3. The purpose of the maintenance operation shown to the
right is ___________________________________
_________________________________________
_________________________________________
_________________________________________
_________________________________________
4. In the picture, the technician rebuilding the converter is
holding the _________________________________
_________________________________________
It should be inspected for _______________________
_________________________________________
_________________________________________
It should be replaced if _________________________
_________________________________________
71
4.0
5. The converter part shown to the right is the ___________
_________________________________________
_________________________________________
_________________________________________
6. The part shown to the right is a ___________________
_________________________________________
_________________________________________
_________________________________________
7. The component in the center of the picture to the right is
the _______________________________________
_________________________________________
_________________________________________
To verify that it is correct for the engine emissions control
system (lean burn, Stoichiometric, etc.), check the ______
_________________________________________
_________________________________________
8. The part shown to the right is the __________________
_________________________________________
The lever should be ___________________________
_________________________________________
It may be bent as the result of ____________________
_________________________________________
_________________________________________
_________________________________________
72
9. After rebuilding an IMPCO 425 mixer and before checking
for proper operation using an engine emissions analyzer, for
initial starting reference the idle adjusting screw may be set
to _______________________________________
from the base of the plate to the top of the head.
The initial base full-load fuel mixture may be pre-set to ___
_________________________________________
measured from the body of the mixer to the top of the
bolt head.
4.2
Lab Activity
Test an Electronic Emissions Control System
for Proper Operation
Directions: Observe the procedures demonstrated by your instructor for setting
up the engine using an emissions analyzer. Use the blank space provided below
Follow any instructions given by your instructor. Be aware of how your actions
may affect others nearby, and how their actions could affect you.
73
4.0
NOTES
74
Appendix A
Glossary of Terms
75
A
GLOSSARY OF TERMS
Air-fuel ratio is frequently used in the analysis of the combustion process. It is usually
AF = (mass of Air) / (mass of Fuel)
or
Air-Fuel Ratio equals
(mass of Air)
(mass of Fuel)
Boiling point is the temperature, at atmospheric pressure, where a liquid changes to a vapor
(gaseous) state.
A 3-way catalytic converter is an exhaust system component (installed downstream of
Reduces nitrogen oxides to nitrogen and oxygen.
Oxidizes carbon monoxide to carbon dioxide.
Oxidizes unburned hydrocarbons to carbon dioxide and water by heat and
chemical reaction.
A converter — vaporizer/pressure regulator uses engine heat (from circulating
coolant) to vaporize liquid propane and then reduces the vapor pressure supplied to the
propane-air mixer.
EGR refers to exhaust gas recirculation, a method that may be used by an engine
manufacturer to reduce NOx compounds in the exhaust gases by decreasing the amount of
oxygen in the combustion chamber. High combustion temperatures are the primary cause of
NOx formation. By recirculating a small amount of exhaust gas back into the cylinders, the
combustion temperature is reduced by eliminating excess oxygen.
An electric lock-off valve
not operating.
Excess air
common to use more air than the stoichiometric amount in the combustion chamber to
increase the chances of complete combustion. Excess air can also be used to provide some
temperature control of the combustion chamber.
76
Glossary of Terms
Hydrostatic protection for liquid piping or hose is a code
requirement to prevent the bursting of piping or hose sections that
contain liquid propane and that can be closed at each end of the
section. If each end of the liquid piping or hose section is closed,
an increase in temperature could result in a pressure increase in
excess of the maximum working pressure rating of the pipe or hose.
Installing a hydrostatic relief valve in the piping or hose section
meets the code requirement for hydrostatic protection.
The Greek letter Lambda (λ) represents the difference between an engine’s actual air-fuel
ratio and its chemically correct (stoichiometric) air-fuel ratio. Lambda ratios greater than
1.0 signify excess air.
A Lambda (λ) sensor may be used to refer to a wide-range oxygen (O2) sensor installed in
the exhaust system as part of the emission control system of a lean-burn engine. The sensor
must be located between the exhaust manifold and upstream of any catalytic converter.
A lean-burn engine for EPA regulatory purposes is an engine with a λ ratio of 1.1 or greater.
An odorant is a chemical compound added to a fuel gas that does not substantially change
the properties of the gas, yet provides a warning that the gas is present in the atmosphere in
the event of a gas leak. Fuel gas odorants are added in a concentration that is detectable by a
fuel gas.
A propane-air mixer is a device in a propane engine fuel system that controls the amounts
of propane and air to provide the desired fuel mixture for combustion.
A pressure-reducing valve is an in-line pressure regulator used to control propane’s vapor
pressure immediately before it enters the propane-air mixer.
Stoichiometric or theoretical combustion is the ideal air-fuel ratio at which a fuel is
burned completely. Complete combustion means all the carbon (C) is oxidized to carbon
dioxide (CO2), all hydrogen (H) is oxidized to water (H2O), and all sulfur (S) is oxidized to
sulfur dioxide (SO2).
If there are unburned components in the exhaust gas, such as C (carbon), H2 (hydrogen), or
CO (carbon monoxide), the combustion process is incomplete.
A
77
A
78
Appendix B
Referenced
Publications and
General Information
79
B
Material Safety Data Sheet – Odorized Propane
CHEMICAL PROPANE AND
COMPANY IDENTIFICATION
Product Name: Odorized
Commercial Propane
Chemical Name: Propane
Chemical Family: Hydrocarbon
Formula: C3H8
Synonyms: Dimethylmethane,
(LPG), Propane, Propyl Hydride
Transportation Emergency No.:
800/424-9300 (CHEMTREC)
COMPOSITION/INFORMATION ON INGREDIENTS
INGREDIENT NAME / CAS NUMBER
Propane/74-98-6
Ethane/74-84-0
Propylene/115-07-1
Butanes/various
Ethyl Mercaptan/75-08-1
PERCENTAGE
87.5–100
0–7.5
0–10.0
0–2.5
16–25 ppm
HAZARDS IDENTIFICATION
Emergency Overview
DANGER!
and all other ignition sources. Vapor replaces
oxygen available for breathing and may cause
adequate ventilation. Odor may not provide
adequate warning of potentially hazardous
concentrations. Vapor is heavier than air.
Liquid can cause freeze burn similar to frostbite.
Do not get liquid in eyes, on skin, or on clothing.
Avoid breathing of vapor. Keep container valve
closed when not in use.
80
OSHA PEL
1,000 ppm
1,000 ppm
1,000 ppm
1,000 ppm
0.5 ppm
Referenced Publications and General Information
POTENTIAL HEALTH EFFECTS INFORMATION
ROUTES OF EXPOSURE:
INHALATION: Asphyxiant. It should be noted that before suffocation could occur,
may cause dizziness. Exposure to atmospheres containing eight percent to ten percent
or less oxygen will bring about unconsciousness without warning, and so quickly that
serious injury or death.
EYE CONTACT: Contact with liquid can cause freezing of tissue.
SKIN CONTACT: Contact with liquid can cause frostbite.
[SKIN ABSORPTION]: None.
[INGESTION]: Liquid can cause freeze burn similar to frostbite. Ingestion not expected
to occur in normal use.
CHRONIC EFFECTS: None.
MEDICAL CONDITIONS AGGRAVATED BY OVEREXPOSURE: None.
OTHER EFFECTS OF OVEREXPOSURE: None.
CARCINOGENICITY: Propane is not listed by NTP, OSHA, or IARC.
FIRST AID MEASURES
INHALATION: Persons suffering from lack of oxygen should be removed to fresh
administer oxygen. Obtain prompt medical attention.
EYE CONTACT:
lukewarm water. Obtain medical attention immediately.
SKIN CONTACT: Contact with liquid can cause frostbite. Remove saturated clothes,
shoes, and jewelry. Immerse affected area in lukewarm water not exceeding 105°F. Keep
immersed. Get prompt medical attention.
INGESTION: If swallowed, get immediate medical attention.
NOTES TO PHYSICIAN: None.
81
B
FIRE-FIGHTING MEASURES
FLASH POINT: –156°F (–104°C)
AUTOIGNITION: 842°F (432°C)
IGNITION TEMPERATURE IN AIR: 920–1120°F
FLAMMABLE LIMITS IN AIR BY VOLUME:
EXTINGUISHING MEDIA: Dry chemical, CO2, water spray or fog for surrounding
SPECIAL FIRE-FIGHTING INSTRUCTIONS: Evacuate personnel from danger area.
Evacuated personnel should stay upwind and away from tank ends, and move to a distance at
(especially upper half) with water spray from maximum distance and the sides of containers,
UNUSUAL FIRE AND EXPLOSION HAZARDS: Propane is easily ignited. It is
heavier than air; therefore, it can collect in low areas while dissipating. Vapors may be
moved by wind or water spray. Vapors may move to areas where ignition sources are
to heat, and container may rupture if pressure relief devices fail to function.
HAZARDOUS COMBUSTION PRODUCTS: In typical use in properly adjusted and
maintained gas appliances — None. If propane combustion is incomplete, poisonous
carbon monoxide (CO) may be produced. Defective, improperly installed, adjusted,
maintained or vented appliances may produce carbon monoxide or irritating aldehydes.
ACCIDENTAL RELEASE MEASURES
STEPS TO BE TAKEN IF MATERIAL IS RELEASED OR SPILLED: Evacuate
the immediate area. Eliminate any possible sources of ignition and provide maximum
ventilation. Shut off source of propane, if possible. If leaking from container or valve,
HANDLING AND STORAGE
HANDLING PRECAUTIONS: Propane vapor is heavier than air and can collect in
off prior to connecting or disconnecting. If container valve does not operate properly,
discontinue use and contact supplier. Never insert an object (e.g. wrench, screwdriver,
pry bar, etc.) into pressure relief valve or cylinder cap openings. Do not drop or abuse
cylinder. Never strike an arc on a gas container or make a container part of an electrical
circuit. See Section 16, OTHER INFORMATION, for additional precautions.
82
STORAGE PRECAUTIONS: Store in a safe, authorized location (outside, detached
should never be allowed to reach temperatures exceeding 125°F (52°C). Isolate from
combustible materials. Provide separate storage locations for other compressed and
oxidizers, by a minimum distance of 20 feet, or by a barrier of non-combustible material
be segregated. Store cylinders in upright position, or with pressure relief valve in vapor
space. Cylinders should be arranged so that pressure relief valves are not directed toward
other cylinders. Do not drop or abuse cylinders. Keep container valve closed and plugged
or capped when not in use. Install protective caps when cylinders are not connected for
use. Empty containers retain some residue and should be treated as if they were full.
EXPOSURE CONTROLS/PERSONAL PROTECTION
ENGINEERING CONTROLS
Ventilation:
Ignition Source Control: Electrical wiring in liquid transfer areas must be Class I,
Group D, and Explosion-proof. Other possible ignition sources should be kept away from
transfer areas. NO SMOKING signs should be posted at all approaches and entries to
and vegetation.
RESPIRATORY PROTECTION (SPECIFY TYPE)
General Use: None.
Emergency Use: If concentrations are high enough to warrant supplied-air or self-
PROTECTIVE CLOTHING: Avoid skin contact with liquid propane because of the
possibility of freeze burn. Wear gloves and protective clothing that are impervious to
the product for the duration of the anticipated exposure.
EYE PROTECTION:
cylinders.
OTHER PROTECTIVE EQUIPMENT: Safety shoes are recommended when
handling cylinders.
83
B
EXPOSURE CONTROLS/PERSONAL PROTECTION
BOILING POINT: @ 14.7 psia = –44°F
SPECIFIC GRAVITY (DENSITY) OF VAPOR (Air = 1) at 60°F: 1.50
SPECIFIC GRAVITY OF LIQUID (Water = 1) at 60°F: 0.504
VAPOR PRESSURE: @ 70°F = 127 psig
@ 105°F = 210 psig
EXPANSION RATIO (From liquid to gas @ 14.7 psia): 1 to 270
SOLUBILITY IN WATER: Slight, 0.1 to 1.0%
APPEARANCE AND ODOR: A colorless and tasteless gas at normal temperature and
pressure. An odorant has been added to provide a strong unpleasant odor.
ODORANT WARNING: Odorant is added to aid in the detection of leaks. One common
odorant is ethyl mercaptan, CAS No. 75-08-01. Odorant has a foul smell. The ability of
people to detect odors varies widely. In addition, certain chemical reactions with material
in the propane system, or fugitive propane gas from underground leaks passing through
certain soils, can reduce the odor level. No odorant will be 100% effective in all
circumstances. If odorant appears to be weak, notify propane supplier immediately.
STABILITY AND REACTIVITY
STABILITY: Stable.
Conditions to Avoid: Keep away from high heat, strong oxidizing agents, and sources
of ignition.
REACTIVITY:
Hazardous Decomposition Products: Products of combustion are fumes, smoke,
carbon monoxide and aldehydes, and other decomposition products. Incomplete
combustion can cause carbon monoxide, a toxic gas, while burning, and may occur
when propane is used as an engine fuel.
Hazardous Polymerization: Will not occur.
TOXICOLOGICAL INFORMATION
Propane is non-toxic and is a simple asphyxiate, however, it does have slight anesthetic
properties and higher concentrations may cause dizziness.
[IRRITANCY OF MATERIAL]
84
[SENSITIZATION TO MATERIAL]
[REPRODUCTIVE EFFECTS]
[TERATOGENICITY]: None
[MUTAGENICITY]: None
[SYNERGISTIC MATERIALS]: None
ECOLOGICAL INFORMATION
No adverse ecological effects are expected. Propane does not contain any Class I or Class
II ozone-depleting chemicals (40 CFR Part 82). Propane is not listed as a marine pollutant
by DOT (49 CFR Part 171).
DISPOSAL CONSIDERATIONS
WASTE DISPOSAL METHOD: Do not attempt to dispose of residual or unused
product in the container. Return to supplier for safe disposal.
Residual product within process system may be burned at a controlled rate, if a suitable
federal, state, and local regulations.
TRANSPORTATION INFORMATION
DOT SHIPPING NAME:
HAZARD CLASS: 2.1 (Flammable Gas)
IDENTIFICATION NUMBER: UN 1075
PRODUCT RQ: None
SHIPPING LABEL(S): Flammable gas
IMO SHIPPING NAME: Propane
PLACARD (When Required): Flammable gas
IMO IDENTIFICATION NUMBER: UN 1978
SPECIAL SHIPPING INFORMATION: Container should be transported in a secure,
upright position in a well-ventilated vehicle.
85
B
REGULATORY INFORMATION
The following information concerns selected regulatory requirements potentially applicable to
their own regulatory compliance on a federal, state [provincial], and local level.
U.S. FEDERAL REGULATIONS
EPA – Environmental Protection Agency
CERCLA – Comprehensive Environmental Response, Compensation, and
Liability Act of 1980 (40 CFR Parts 117 and 302)
SARA – Superfund Amendment and Reauthorization Act
(TPQ) and release reporting on reportable quantities (RQ) of EPA extremely
hazardous substances (40 CFR Part 355).
appear in 40 CFR Part 372. Propane does not require reporting under Section 313.
40 CFR PART 68 Risk Management for Chemical Accidental Release
TSCA – Toxic Substance Control Act
Propane is not listed on the TSCA inventory.
OSHA – Occupational Safety and Health Administration
FDA – Food and Drug Administration
when used as a propellant, aerating agent, and gas.
86
OTHER INFORMATION
SPECIAL PRECAUTIONS: Use piping and equipment adequately designed to
withstand pressures to be encountered.
NFPA 58
and OSHA 29 CFR 1910.110 require that all
persons employed in handling LP gases be trained in proper handling and operating
procedures, which the employer shall document. Contact your propane supplier to arrange
propane containers and systems.
WARNING: Be aware that with odorized propane, the intensity of ethyl mercaptan stench
(its odor) may fade due to chemical oxidation (in the presence of rust, air, or moisture),
adsorption, or absorption. Some people have nasal perception problems and may not be able
to smell the ethyl mercaptan stench. Leaking propane from underground lines may lose its
odor as it passes through certain soils. While ethyl mercaptan may not impart the warning of
the presence of propane in every instance, it is generally effective in a majority of situations.
Familiarize yourself, your employees, and customers with this warning and other facts
associated with the so-called odor-fade phenomenon. If you do not already know all the facts,
contact your propane supplier for more information about odor, electronic gas alarms, and
other safety considerations associated with the handling, storage, and use of propane.
This material safety data sheet and the information it contains is offered to you in good faith
as accurate. Much of the information contained in this data sheet was received from outside
sources. To the best of our knowledge this information is accurate, but the Propane Education
& Research Council does not guarantee its accuracy or completeness. Health and safety
precautions in this data sheet may not be adequate for all individuals and/or situations. It is
the user’s obligation to evaluate and use this product safely, comply with all applicable laws
and regulations, and to assume the risks involved in the use of this product.
NO WARRANTY OF MERCHANTABILITY, FITNESS FOR ANY PARTICULAR PURPOSES,
OR ANY OTHER WARRANTY IS EXPRESSED OR IS TO BE IMPLIED REGARDING
THE ACCURACY OR COMPLETENESS OF THIS INFORMATION, THE RESULTS TO BE
OBTAINED FROM THE USE OF THIS INFORMATION OR THE PRODUCT, THE SAFETY
OF THIS PRODUCT, OR THE HAZARDS RELATED TO ITS USE.
The purpose of this MSDS is to set forth general safety information and warnings related to
the use of propane. It is not intended to be an exhaustive treatment of the subject, and should
not be interpreted as precluding other authoritative information, or safety procedures that
would enhance safe LP-gas storage, handling, or use. Issuance of this MSDS is not intended
nor should it be construed as an undertaking to perform services on behalf of any party either
for their protection or for the protection of third parties. The Propane Education & Research
Council assumes no liability for reliance on the contents of this material safety data sheet.
87
B
Estimating Propane Supply Tank Vaporization
“RULE OF THUMB” ESTIMATED VAPORIZATION RATES FOR 500 AND 1,000 WATER
GALLON ABOVEGROUND ASME TANKS @ 20°F AMBIENT TEMPERATURE (Btu/hr)
Liquid
Propane in
Tank
Tank Capacity
(Gal. Water Capacity)
500
1,000
60%
880,000
1,590,800
50%
779,200
1,431,720
40%
710,400
1,272,640
30%
621,600
1,113,560
20%
532,800
954,480
1. Vaporization rates shown in Btu/hr will decrease
with increasing relative humidity if frost forms
on the tank, decreasing heat transfer to the
liquid propane.
2. Conversely, vaporization rates may increase at
ambient temperatures above 20°F.
3. Estimates are based on 20°F differential
between tank’s wetted surface area temperature
and the liquid propane’s temperature.
4. If a single tank cannot supply engine vapor
demand, there are two available options:
Manifold two (or more) tank’s vapor service.
Utilize liquid service and use engine heat to
vaporize the liquid propane.
Engine and Propane Fuel System Original Equipment
Manufacturer [OEM] Contact Information*
88
Engine OEMs
Contact Information
E-Mail Contact
Anderson Industrial Engines Co.,
Inc.
5532 Center Street
Omaha, NE 68106
(402) 558-8700
www.ai-engines.com
[email protected]
Buck's Engines
515 North I-27
Lubbock, TX 79403
806-762-0455
www.bucksengines.com
[email protected]
IMPCO Technologies
7100 E, 15 Mile Road
Sterling Heights, MI 48312
(586) 264-1200
www.impco.ws
[email protected]
Industrial Irrigation
Highway 6, 221 East J Street
Hastings, NE 68901
(402) 463-1377
www.industrial-irrigation.com
[email protected]
Kem Equipment, Inc.
10800 S.W. Herman Road
Tualatin, OR 97062
(503) 692-5012
www.kemequipment.com
(See Web site contact page.)
TGP West, Inc.
3250 El Camion Real Suite F3
Atascadero, CA 93422-2501
(805) 462-2849
www.tgpwest.com
Propane Fuel System OEMs
Contact Information
E-Mail Contact
Continental Controls Corporation
8845 Rehco Road
San Diego, CA 92121
(858)453-9880
www.continentalcontrols.com
IMPCO Technologies
3030 South Susan Street
Santa Ana, CA 92704
(714) 656-1200
www.impco.ws
Woodward Governor Company
P.O. Box 1519
1000 East Drake Road
Fort Collins, CO 80525
(970) 482-5811
www.woodward.com
*This list of manufacturers is not exhaustive, and listing here does not constitute an endorsement or recommendation.
Likewise, if an engine or propane fuel system manufacturer is not listed here it should not be inferred that such
manufacturer’s products are considered to be less serviceable, reliable, or suitable.
For Information on the E-Com JN Emissions Analyzer:
ECOM America, Ltd.
1628 Oakbrook Drive
Gainesville, GA 30507
[email protected]
For Information on the Bridge Analyzer:
Bridge Analyzers, Inc.
1805 Clement Avenue
Alameda, CA 94501
[email protected]
89
B
Typical Propane Irrigation/Large Generator Engine
Maintenance Schedule*
INTERVAL
300 hours
1,000 hours
MAINTENANCE REQUIREMENTS
Adjust fuel pressure
Adjust fuel mixture
Repair any leaks
Maintain coolant level
Oil reservoir level
Monitor oil
consumption
Tighten all bolts &
clamps
restriction
Battery water level Vibration test
Inspect damper
Clean and wash
unit Maintain
gearhead oil level
Adjust overhead
Maintain coolant
mixture
Compression test
Adjust overhead
oilers
Coolant system
pressure check
All preceding
service
Lube and inspect
U-joints
Check all hoses
Oil analysis
program
Drain catch tray
and skid
Repair any failed
component
Dispose of all
Adjust belts
All preceding service
1,500 hours
Starter draw test
Spark plugs
3,000 hours
Replace gearhead oil
5,000 hours
Replace belts
Replace hoses
Clean battery
connections
All preceding
service
10,000 hours
Replace universal
joints
Replace batteries
Replace water pump
Replace
thermostat
All preceding
service
20,000 hours
Replace damper
Overhead overhaul
30,000 hours
Major overhaul
Cylinder leakdown test
Test ignition
performance
Adjust Timing
*Propane engine maintenance schedule supplied by TGP West, Inc. in Atascadero, Calif., a major supplier of
propane engines since 1994. For more information, contact (805) 462-2849.
90
Appendix C
Educational Materials
91
C
A Message to Instructors
This course of instruction was designed to provide introductory level material for agricultural
service technicians, particularly service personnel who typically work for irrigation, pump,
and equipment/implement suppliers. In-depth training is available from propane carburetion
equipment manufacturers and may be offered by some stationary agricultural engine suppliers.
A goal for this course is to provide a preliminary level of training within an eight-hour time
frame. For the personal safety of technicians who may be called upon to work on propane
the propane Material Safety Data Sheet located in Appendix B.
Lab Activities at the end of each section are designed to simulate hands-on learning activities
for participants where stationary engines and propane fuel systems are not readily available.
Instructors should adapt the lab activities to provide actual hands-on experiences where
additional resources are available (for example, propane fuel-system components, cut-away
models, actual fuel-supply tanks, engines, electrical generators and irrigation sets, etc.).
Propane Education & Research Council (202) 452-8975 www.agpropane.com
A Training Quiz (Documentation of Training) is provided on the following pages to generate
a training record for participants and their employers.
This quiz is to be completed by the attendee receiving this manual at the end of the
training session or at the end of each section, as determined by the instructor.
The quiz must be corrected and signed by both the attendee and the instructor to verify
participation in this training course.
The quiz is designed for removal to allow for retention by the employer as documentation
of training. It is suggested that the participating individual (attendee) also retain a copy
for his or her own records.
92
This Training Quiz
your place of employment. It is also recommended that you keep a copy for yourself.
Except for the signature blanks, please PRINT ALL of the information requested in this
_______________________________________________________
_____________________________________________________
___________________________________________________
________________________________________________
Chapter 1
Directions: Each incomplete statement or question is followed by a list of responses. Select
the response that most correctly completes the statement or answers the question. Mark your
choice by placing an X in the parentheses to the left of the letter of your response [(X)].
1. What document gives safety information concerning the transferring, handling, and
storing of propane and should be available to employees where these activities occur?
(
(
(
(
) a.
) b.
) c.
) d.
Chemical Abstract for propane
Material Safety Data Sheet for propane (MSDS)
Community Right-to-Know Form
DHS Tier I Filing Form
2. What is propane’s boiling point?
(
(
(
(
) a.
) b.
) c.
) d.
31°F
–256°F
–44°F
0°C
3. A tank’s propane vapor pressure on a hot summer day will be approximately what?
(
(
(
(
) a.
) b.
) c.
) d.
200 psi
30 psi
70 psi
10 psi
93
C
Please PRINT your name and enter today’s date.
Your Name:
Date:
4. What is added to propane to make it likely that people will detect a leak?
(
(
(
(
) a.
) b.
) c.
) d.
An odorant
A dye
An eye and skin irritant
A water-reactive compound
5. What is propane’s liquid to vapor expansion ratio? (That is, if a given volume of liquid
propane is released to the atmosphere, how much propane vapor will result?)
(
(
(
(
) a.
) b.
) c.
) d.
1 to 10
1 to 270
1 to 100
1 to 27
6. If your skin or other tissues contact liquid propane, what if any physical condition
will result?
(
(
(
(
) a.
) b.
) c.
) d.
Nothing
Spontaneous combustion
Corrosive burns
Frostbite
7. How does the weight of propane vapor compare to the weight of air?
(
(
(
(
) a.
) b.
) c.
) d.
Propane and air weigh about the same.
Propane, like natural gas, is lighter than air.
Propane is heavier than air.
Air is 1.5 times heavier than propane vapor.
8. When propane is purged from a fuel system, where should the purged gas be directed?
( ) a. Away from ignition sources
( ) b. Outdoors
( ) c. Both a and b
94
Your Name:
Date:
9. Is the propane tank pictured below used in vapor service or liquid service?
( ) a. Vapor service
( ) b. Liquid service
( ) c. Both vapor and liquid service
10. Before performing a maintenance operation that requires disconnecting or disassembling
a propane fuel-system component, what must the technician verify?
(
(
(
(
) a.
) b.
) c.
) d.
Determine if any components are in warranty
Determine that pressure is reduced to atmospheric pressure
Determine if any component is subject to recall
Determine the grade of propane supplied to the system
95
C
Your Name:
Date:
Chapter 2
1. What causes liquid propane in a sealed container to vaporize?
(
(
(
(
) a.
) b.
) c.
) d.
Decrease in container pressure
Increase in container pressure
Decrease in container temperature
Increase in liquid volume
2. What is required for propane vaporization?
(
(
(
(
) a.
) b.
) c.
) d.
High relative humidity in air
Low relative humidity in air
Heat transfer
High air temperature
3. Of these propane fuel-system components, which is not typically used on small
air-cooled engines?
(
(
(
(
) a.
) b.
) c.
) d.
Electric lock-off valve
Pressure regulator
Converter
Pressure-reducing valve
4. What functions are performed by a typical vacuum lock-off?
( ) b. Filter small particles out of the fuel to protect other components
( ) c. Verify that engine vacuum is adequate for complete combustion
( ) d. Both a and b
5. In the case of engines operating on propane vapor supplied by the fuel tank, what is the
(
(
(
(
96
) a.
) b.
) c.
) d.
2 psi
Within a range of 5 to 10 psi
20 psi
30 psi
Your Name:
Date:
6. What is the function of a converter in a propane fuel system?
volume of fuel required
( ) b. Controlling the vapor pressure of the fuel supplied to the engine’s propane-air
mixer
( ) c. Preventing the buildup of “heavy ends” in the fuel system
( ) d. Both a and b
7. Of the following, which DIRECTLY relates to propane engine fuel-systems?
(
(
(
(
) b.
) c.
) d.
) e.
NFPA 10, Installation, Maintenance, and Use of Portable Fire Extinguishers
NFPA 30, Flammable and Combustible Liquids Code
NFPA 70, National Electrical Code
Both a and b
Chapter 3
40 CFR §60.4248?
(
(
(
(
) a.
) b.
) c.
) d.
Stoichiometric
Rich-burn engine
Lean-burn engine
All of the above
2. When stoichiometric combustion of propane occurs, what are the primary products of
combustion?
(
(
(
(
(
(
(
) a.
) b.
) c.
) d.
) e.
) f.
) g.
Carbon monoxide
Hydrocarbons
Carbon dioxide
Water vapor
a and d
c and d
a and b
97
C
Your Name:
Date:
3. What is the Greek letter used for the ratio of fuel to air in relation to stoichiometric?
( ) a. λ
( ) c.
( ) d.
β
Φ
combustion products?
(
(
(
(
) a.
) b.
) c.
) d.
HC, NOx, O2, CO, CO2
HC, NOx, H2O, CO, CO2
C3H8, NOx, H2O, CO, CO2
NH3, NOx, O2, CO, CO2
5. What emission control system component changes exhaust CO to CO2 and reduces the NO
and NO2 to N2 and O2?
(
(
(
(
) a.
) b.
) c.
) d.
O2 sensor
Catalytic converter
Air mass sensor
Lambda sensor input processor
6. What is an important advantage of running an engine in the lean-burn mode?
( ) a. Decreased fuel consumption
( ) b. Increased power
( ) c. Fewer engine components required
7. What emissions operating term would apply to engines that are not equipped with
electronic microprocessor fuel-air mixture and emissions controls?
( ) a. Open loop
( ) b. Closed loop
98
Your Name:
Date:
8. What emissions operating term would apply to engines after reaching operating
temperature and when fuel-air mixtures, cylinder charging, and spark timing are
varied in response to exhaust gas sensor and other sensor outputs, as they are read
and interpreted by one or more microprocessors?
( ) a. Open loop
( ) b. Closed loop
9. What emissions sensor initially generates the signal to switch to closed-loop mode in most
emission control systems?
(
(
(
(
) a.
) b.
) c.
) d.
RPM reference
O2 sensor
Throttle position sensor
Coolant temperature sensor
10. More precise control of the air-fuel mixture is possible when the processor, resulting in
more accurate outputs to manage the combustion process.
(
(
(
(
) a.
) b.
) c.
) d.
Can be manually bypassed
Inputs are taken downstream of any catalytic converter
Can receive more information (inputs)
Is not tied to any of the traditional engine-protection switches
Chapter 4
1. Of the following engine operating faults, which can be corrected by repairing/replacing a
propane fuel-system component?
(
(
(
(
) a.
) b.
) c.
) d.
Inoperative or defective engine safety switch
Fault in the ignition system
Disconnected, damaged, or leaking vacuum hose or connection
Seized air valve in an air valve-equipped mixer
99
C
Your Name:
(
(
(
(
) a.
) b.
) c.
) d.
Date:
Excessive turbocharger noise on an engine so equipped
Bulge or unusual casing expansion in fuel hose
Filter body is cold or is sweating during loaded engine operation
Propane venting from converter
3. What is the most common cause of an inoperative electric lock-off?
(
(
(
(
) a.
) b.
) c.
) d.
Lack of adequate electrical ground
Defective seat disc
Failure of the ignition coil
Broken solenoid coil winding
4. What is the most common cause of an inoperative vacuum lock-off?
(
(
(
(
) a.
) b.
) c.
) d.
Engine runs, but compression is low
Improper engine coolant mixture
Oil pressure is abnormally high
Cut, cracked, or disconnected vacuum line
5. Is the following statement true or false? Propane vapor pressure regulators used with
propane engine fuel systems are adjustable, but rarely need adjusting after the initial setup
unless engine no-start, hard-start, or slow-start, conditions develop.
( ) a. True
( ) b. False
6. To properly diagnose propane fuel-system operating conditions, the technician should have
typical mechanic’s tools, suitable pressure gauges with adapters, a water column manometer
capable of positive and negative pressure readings, a good quality DVOM, and _________.
( ) a. A distributor balancing machine
( ) b. An electronic ignition analyzer
( ) c. A hydrometer rated for high-pressure service
100
Your Name:
(
(
(
(
) a.
) b.
) c.
) d.
Date:
Manufacturer’s instructions and technical manuals
State air quality board regulations
EPA air quality regulations
ASE and SAE technical bulletins
8. What feature of an air-gas valve affects the propane-air mix at idle?
( ) a. Taper of the valve
( ) b. Length of the notches
( ) c. Diaphragm material used on the air valve
( ) e. Both a and b
9. What is the recommended installation orientation for a typical propane-air mixer that uses
an air valve?
(
(
(
(
) a.
) b.
) c.
) d.
Vertical
Horizontal
Horizontal to diagonal
No orientation recommendation applies
stoichiometric fuel-air engine operation?
( ) a. Yes
( ) b. No
11. Which of the following propane fuel-system components plays the largest part in
determining if the engine is a lean-burn, rich-burn, or stoichiometric engine?
(
(
(
(
) a.
) b.
) c.
) d.
Filter/lock-off
Pressure regulator
Propane-air mixer
Throttle body
101
Notes
102
103
Propane Education & Research Council
1140 Connecticut Avenue, N.W. Ste. 1075
Washington, D.C. 20036
(202)452-8975
©2009 Propane Education & Research Council [36801-2/09]
PRC 003900

Maintaining and Repairing Propane Fuel Systems on Stationary

Transcription

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