MaintainingRepairing PropaneStationaryEngines

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 QGXVHIXOLQLPSOHPHQWLQJDSSOLFDEOHFRGHVVWDQGDUGVDQGOHJDOUHTXLUHPHQWV7KLVPDWHULDOLVQRWintended 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)

Maintaining and Repairing Propane Fuel Systems on Stationary Engines

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 propanes 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 HQJLQHIXHOV\VWHPVDVWKH\DUHW\SLFDOO\FRQJXUHGIRUWKHIROORZLQJNLQGVRIHQJLQHV Air-cooled engines, often called small engines and used in electrical generators. Liquid-cooled engines, typically used with larger electrical generators and irrigation pumps.

'HQLWLRQVIRUWHUPVSULQWHGLQHLWKHUblue 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.

AcknowledgmentsThe 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 HaleTGP West Inc., 3250 El Camino Real, Suite 3, Atascadero, CA 93422 (805) 465-2849www.tgpwest.com

Rich Fisher and Dave CampbellContinental Controls Corporation, 8845 Rehco Road, San Diego, CA 92121 (858) 453-9880 www.continentalcontrols.com

Franz HofmannRailroad Commission of Texas, Alternative Fuels Research & Education Division, 6506 Bolm Road, Austin, Texas 78721 (512) 463-8501 [email protected]

Richard DlugoszSherwood 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 DVVLVWDQFHLQGHYHORSLQJWKHSURMHFWDQGDUUDQJLQJIRUSUHSXEOLFDWLRQHOGWHVWLQJRIWKHWUDLQLQJPDWHULDOV

ABOUT THE PROGRAM

Table of Contents

1.0 Physical Properties of Propane and Safety Precautions to Apply

2.0 Characteristics of Propane Fuel Systems for Stationary Engines

3.0 Propane-Fueled Stationary Engine Emission Control Systems

4.0 Propane-Fueled Engine Fuel System Maintenance and Repair

Appendix A: Glossary of Terms

Appendix B: Referenced Publications and General Information

Appendix C: Educational Materials

1

11

23

37

75

79

91

1Physical Properties of Propane and Safety Precautions to Apply

1.0

21.0

Working safely to maintain or repair propane fuel systems on stationary engines requires service personnel to be familiar with propanes 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

3URSDQHLVFODVVLHGDVDKD]DUGRXVPDWHULDO%\ODZDMaterial 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.

7KLVFKDSWHUZLOOGLVFXVVVSHFLFLQIRUPDWLRQIURPWKHMSDS 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 (44F), pressure-tight containers are used. Propane liquid stored in these containers at temperatures at or above 44F 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. Propanes 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 2530 pounds per square inch. (See the chart on the next page.)

INTRODUCTION


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.

41.0

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 C3H8 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 8293 95104 With octane being a measure of a fuels resistance to knock, propane can stand higher compression pressure and more initial advanced spark timing than gasoline.

Energy Density(Btu / Lb)LowerHigher(Btu / Gal)

(Btu / Cu Ft)LowerHigher

19,00020,360114,000

Not ApplicableNot Applicable

19,92021,65091,500

24882520

High hydrogen-to-carbon ratio fuels produce more heat per pound.

High carbon-to-hydrogen ratio fuels have more heat energy per gallon.

6SHFLF*UDYLW\

(Vapor)3.5 1.5 Both fuels vapors are heavier than air (1.0).

6SHFLF*UDYLW\

(Liquid)0.739 0.51 In liquid form, both gasoline and propane are lighter

than water (1.0).

Boiling Point 80 to 440F 44F Above 44F, 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

5DQJHRIDPPDELOLW\OLPLWVDUHIURPOHDQHVW

combustible mixture to the richest combustible mixture.

Stoichiometric Combustion Air : Fuel Required by Weight

14.7 : 1 15.5 :1 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 FRQQHGDUHD7KHUHIRUHDYRLGLQKDOLQJSURSDQH

Propane vapor is 1.5 times heavier than air. If released into still air, it may initially FRQFHQWUDWHLQORZO\LQJDUHDV+RZHYHULIWKHUHLVVXIFLHQWDLUPRYHPHQWHVSHFLDOO\outside, the vapor should dissipate in the air.

When the physical and combustion properties of propane are considered together, these KD]DUGVFDQEHLGHQWLHGIRUDQXQFRQWUROOHGUHOHDVHRISURSDQH

Chemical hazards 3URSDQHLVKLJKO\DPPDEOHDQGSUHVHQWVULVNRIUH 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 UHVXOWLQ\LQJSDUWVRUSURGXFWSURSHOOHGXQGHUSUHVVXUH

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.

61.0

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.

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.

A domestic ASME tank is typically used to supply propane vapor through the vapor VHUYLFHYDOYHDQGDUVWVWDJHpressure 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.

Vinyl Gloves

Safety Glasses

Acoustical Ear Muff and Ear Plugs for Hearing Protection

Typical ASME Tank Valve and Fitting Connections

Tank Valves and Fittings Connected to the Tanks Vapor Space

Tank Liquid Withdrawal Excess Flow Valve. If a valve is installed here, it is connected to the tanks 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 RXWGRRUVLQXQFRQQHGDQGRHSQVSDFHthat 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.

$VLWDSSOLHV a. Close any liquid service valve(s) that

FRQWUROVSURSDQHOLTXLGRZWROLTXLGcooled engines used to drive irrigation pumps or large electrical generators.

b. Close any vapor service valve(s) that FRQWUROVSURSDQHYDSRURZWRWKHengine.

81.0

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 IDFLOLWDWHVHUYLFHRSHUDWLRQVVXFKDVOWHUelement 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.

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.

6WRSWKHRZRISURSDQHIURPWKHVXSSO\WDQNWRWKHHQJLQHIXHOV\VWHP)RU9DOYH$DQGfor Valve B shown below, place a in the box next to the correct answer.

Valve A. O Propane Liquid O Propane VaporO Propane Liquid O Propane Vapor Valve B.

2. Applying your employers 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. B.

C.

Purging liquid propane (high pressure) O O OPurging propane vapor (reduced pressure) O O O

VinylGloves

EyeProtection

HearingProtection

10

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. 9DOYHVWRFORVHWRVWRSSURSDQHRZIURPWKHVXSSO\WDQNV 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.

11

Characteristics of Propane Fuel Systems for Stationary Engines

2.0

12

2.0

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.

The objectives of this chapter are to: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 glycol-water 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 engines 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 materials 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 liquids boiling point; boiling of WKHOLTXLGVWRSVDIWHUWKHVWRUDJHFRQWDLQHULVOOHGZLWKliquid and vapor and, the balance of heat and pressure forces results in the ceasing of vaporization.

INTRODUCTION

13


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 containers YDSRUL]DWLRQFDSDFLW\/LPLWLQJIDFWRUVDUH

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 FOLPDWHVW\SLFDOO\QGWKDWSURSDQHYDSRUL]HGLQWKHIXHOVXSSO\WDQNLVVXIFLHQWWRSURYLGHDGHTXDWHYROXPHRISURSDQHvapor 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

14

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 manufacturers 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 FLUFXLWLVDFRGHUHTXLUHPHQWWRHQVXUHWKDWSURSDQHRZLVVWRSSHGZKHQWKHHQJLQHLVQRWoperating.

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 engines piston intake stroke.

15


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 1525 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.

16

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 IXHOV\VWHPXVLQJOLTXLGFRRODQWWRFRQYHUWSURSDQHOLTXLGWRYDSRUFRQVLVWVRI

Important Propane Fuel-System Components

There are requirements for LP-gas hose or metallic piping conveying propane OLTXLGWRWKHORFNRIIIXHOOWHU

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).

17


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 VWRSVWKHRZRIOLTXLGSURSDQHZKHQWKHengine 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 7KHZKLWHFRWWRQOWHUHOHPHQWand 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 RULFHVLQWKHORFNRIIRUGRZQVWUHDP pressure regulators.

Cutaway View of Vacuum Lock-off Filter

18

2.0

Converter for Engines up to 110 Brake HorsepowerExamples: 1.5L Inline 4-Cylinder Through

4.3L V-6 Engines

Converter for Engines up to 350 Brake Horsepower,up To and Including 8L Engines

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.

Engine displacement volume of all cylinders.

Vapor-combustion air mixture demand throughout the engines power range.

The cutaway drawing to the ULJKWLOOXVWUDWHV

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 1 to 3 psi.

Heat is transferred from the circulating coolant (green) through metal jacket walls into the vaporizing liquid (medium blue).

19


IMPCO Model 100 Propane-Air Mixer for Engines up to 106 Brake Horsepower

IMPCO Model 125 for Engines up to 126 Brake Horsepower

2. Vapor Pressure Regulator After the propane passes through the primary pressure UHGXFWLRQVWDJHIXUWKHURZLVVWRSSHGE\WKHVHFRQGVWDJHSUHVVXUHVHDW

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.

20

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.

$QDLUYDOYHPL[HUXVHVDGLDSKUDJPRUDSLVWRQZLWKPHWHUHGRULFHVWKDWWUDQVIHUORZpressure 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 HQJLQHVDQGIXWXUHHPLVVLRQVUHGXFWLRQVZLOOEHEULH\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.

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 EHHQWKHVXEMHFWRIUHVHDUFKDQGGHYHORSPHQWE\DQXPEHURIUPVDQGRUJDQL]DWLRQV2IWKHapproaches 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 HIFLHQF\DFURVVWKHZLGHVWUDQJHRISHUIRUPDQFHUHTXLUHPHQWV

9HKLFOHHQJLQHRSHUDWLQJUHTXLUHPHQWVPRUHFORVHO\UHODWHWRWKHSRWHQWLDOEHQHWVWKDWpropane injection seems to offer. Consequently, propane injection systems are not currently offered for stationary engine applications. Stationary spark ignition engines function well with

Continental Controls Corp EGC2 Electronic Gas Carburetor for Lean

Burn Engine missions Control

21


OHVVH[SHQVLYHDQGFRPSOH[SURSDQHIXHOV\VWHPVGXHWRWKHLURSHUDWLQJFKDUDFWHULVWLFV

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 REWDLQWKHKLJKHVWEHQHWWRFRVWUDWLRVIURPPRUHFRPSOH[IXHOLQMHFWLRQV\VWHPV

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 LQVWDOODWLRQRUDV\VWHPPRGLFDWLRQ

National Fire Protection Association (NFPA), 1 Batterymarch Park, Quincy, MA 02169-7471www.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 1)3$ /LTXHHG3HWUROHXP*DV&RGH 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 LVDYDLODEOH

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

22

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 compo-nents 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.

23

Propane-Fueled Stationary Engine

Emission Control Systems

3.0

24

3.0

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.

The objectives of this chapter are to: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 EPAs 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.

EPAs regulations are found in Title 40 of the Code of Regulations, and can be accessed on the internet via www.epa.govRUE\JRLQJWRWKH*RYHUQPHQW3ULQWLQJ2IFH*32:HEVLWHat http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&tpl=%2Findex.tpl.

INTRODUCTION

25

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 spark-LJQLWLRQVWDWLRQDU\HQJLQHV 40 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.

26

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.

,PSRUWDQWWHUPVDQGGHQLWLRQVWKDWDUHXVHGLQ(3$UHJXODWLRQVDUHOLVWHGLQ$SSHQGL[$LQWKH*ORVVDU\6HFWLRQDWWKHHQGRIWKLVPDQXDO7KHIROORZLQJDUHDPRQJWKHWHUPVGHQHGin 40 CFR 60.4248 that should be understood by technicians servicing stationary engines UHJXODWHGE\(3$

Stoichiometric means the theoretical air-to-fuel ratio required for complete combustion. Rich-burn engine means any four-stroke spark-ignited engine where the manufacturers 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 QRWPHHWWKHGHQLWLRQRIDULFKEXUQHQJLQH

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.

27


Excess air ratio is referred to as Lambda (). Stoichiometric air-fuel ratio is 1.0 (the blue line) LQWKHJXUHRQSDJH5LFKEXUQRSHUDWLRQLVWRWKHOHIWRIWKHVWRLFKLRPHWULFSRLQWDQGlean-burn operation is any ratio to the right of the stoichiometric point. (For EPA regulatory purposes, a lean-burn engine is one with a 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 DQGGLGQWGHWRQDWHRUPLVUHWKHLURZQHUVDQGRSHUDWRUVZHUHVDWLVHG

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.

7KHVHYHH[KDXVWJDVHVDUHW\SLFDOO\PHDVXUHGGXULQJFRPEXVWLRQDQDO\VLVZKLOHVHWWLQJXSDQHQJLQHLQWKHHOGRUZKHQYHULI\LQJSURSHURSHUDWLRQRIDQHQJLQHGXULQJSHULRGLFPDLQWHQDQFH

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).

7KHUVWVWUDWHJ\LVVWRLFKLRPHWULFRUULFKEXUQFRPEXVWLRQ7KHVHFRQGVWUDWHJ\LVFDOOHGlean-burn combustion.

1. Rich-Burn Combustion 7KHUVWPHWKRGDQGHDVLHVWWRLPSOHPHQWZDVWRRSHUDWH 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.

28

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 O2VHQVRUVDUHXVHGIRUVSHFLFDSSOLFDWLRQVZKHUHH[WUHPHIXHOPL[WXUH 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 2QHRIWKHEHQHWVRIHQJLQHVUXQQLQJLQDULFKEXUQ 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 NOxLVFRQYHUWHGUVWWKHQ+&DQG&2DUH 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 FRQYHUVLRQ7KLVLVGLIFXOWWRDFFRPSOLVKZLWKDIXOO\PHFKDQLFDOV\VWHPVLQFHWKHDLU fuel mixtures can vary outside of the desired range of the catalyst due to component age DQGZHDUIXHOFRPSRVLWLRQYDULDWLRQVDQGDPELHQWWHPSHUDWXUHXFWXDWLRQV 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 HQJLQHZLWKDVPXFKH[FHVVDLUDVSRVVLEOH7RSUHYHQWHLWKHUNQRFNLQJRUPLVULQJWKH 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 IXHORZDLUJDVPL[WXUHDQGLJQLWLRQWLPLQJ Many engines running in excess lean-burn mode utilize a turbocharger to bring the engine power back to normal levels.

29


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 GRHVQRWKDYHVXIFLHQWRSHUDWLRQDOUHVROXWLRQLQOHDQPRGH

b. %HQHWVRI/HDQ%XUQ 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.

30

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 fuel-FRQWUROYDOYHPD\WDNHDQ\RIWKHVHIRUPV

a. 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 PRYDEOHVOLGHDGLJLWDOO\FRQWUROOHGVWHSSHUPRWRUWKDWFRQWUROVDYDULDEOHRULFHRUan 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.

$W\SLFDOFRQWUROPRGXOHUHDGVRXWSXWVIURPWKHIROORZLQJGHYLFHV

Oxygen sensor the primary emission control system sensor, which is installed in the exhaust system between the engine DQGDQ\FDWDO\WLFFRQYHUWHUDQGRUPXIHU

RPM reference sensor typically LQVWDOOHGDWWKH\ZKHHOIURQWEDODQFHUmagneto, 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.

31


Coolant temperature sensor Measuring engine operating temperature is critical to delivering the proper air-fuel mixture. Cold engines typically require a slightly richer air-fuel mixture than engines that have reached the proper operating temperature. Gaseous-fuel 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

2SHQORRSRSHUDWLRQLVXVHGLQWZRZD\VUHODWHGWRHQJLQHHPLVVLRQFRQWUROV\VWHPV

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 160F engine coolant temperature. If the O2 sensor has reached the proper operating temperature (generally at or around 600F), 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 WRDOORZVXIFLHQWKHDWLQJRIWKHH[KDXVWFDWDO\VW

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.

32

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. 0DVVDLURZVHQVRU0$)

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 YDSRUL]HUDOWHULQJGHOLYHU\SUHVVXUHZKLFKFKDQJHVWKHQDODPRXQWRIIXHOGHOLYHUHGWRWKHengine. Other controls use an electric or vacuum-operated valve, which mounts in the pipe EHWZHHQWKHQDOUHJXODWRUDQGWKHHQJLQHFDUEXUHWRUPL[HU7KLVPRWRUZLOORSHQRUFORVHchanging the volume of propane and the vacuum signal seen between the regulator/vaporizer and the engine/mixer.

33


Emission Control System Components Illustrated

The numbered components on the picture above are:

No. Component Function1. Mixer assembly (Woodward, N-CA200) 3URYLGHVVSHFLHGHQJLQHIXHODLUPL[WXUH2. 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)

6WRSVWKHRZRISURSDQHZKHQWKHHQJLQHLV 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 plugs6. Control module Converts O2 sensor and other inputs to fuel system

operating commands7. 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 VHQVRULVPRXQWHGDIWHUWKHH[KDXVWFDWDO\VW7KLVVHQVRUPRQLWRUVWKHHIFLHQF\RIWKHH[KDXVWFDWDO\VW,IWKHVHFRQGDU\VHQVRUSURGXFHVDFRQVLVWHQWUHODWLYHO\DWRXWSXWVLJQDOthe catalyst is working properly. If the secondary sensor produces an output signal that closely follows the primary sensor, the exhaust catalyst is not working.

34

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, DGLDJQRVWLFVFDQQHUPD\VKRZ%6LQGLFDWLQJWKHUVW22 sensor in the cylinder bank where WKHF\OLQGHULVORFDWHG,QWKLVH[DPSOH%6LVWKHUHDUVHQVRU%6LQGLFDWHVWKHUVWsensor 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 Function1. Original crankshaft position sensor Provides ignition timing inputs 2. Engine RPM reference for the Murphy panel Monitors engine and provides engine over rpm

protection; may also provide input to control module3. Ignition module Provides ignition timing to DIS coils4. O2 sensor Monitors O2 in exhaust gases, inputting to air-fuel

control processor built into component number 55. Unitized carburetor, pressure regulator,

air-fuel mixerProvides 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

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.

35


3.0 Lab Activity

Identify the Components of an Emissions Control System and Each Components 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 components function.

Component Function1234567

36

3.0

2. Fill in the numbered blanks below the picture to identify each numbered component and emission control and the components function.

Component Function123456

37

Propane-Fueled Engine Fuel System

Maintenance and Repair

4.0

38

4.0

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.

The objectives of this chapter are to: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 fuel-system 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), DPHFKDQLFORRNHGIRUSURSHUHQJLQHRSHUDWLRQLQWKHIROORZLQJDUHDV

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 UHGXFHKDUPIXOH[KDXVWHPLVVLRQVKDYHDGGHGDQRWKHUFULWHULRQWKDWPXVWEHH[DPLQHG

Electronic sensors and controls (to more precisely regulate fuel and air mix, ignition, and combustion timing).

INTRODUCTION

39

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 OLVWHG3URSDQHIXHOV\VWHPDQGHQJLQHRULJLQDOHTXLSPHQWPDQXIDFWXUHUV2(0VSHFLFDWLRQVand recommendations should guide in the selection of diagnostic tools and test equipment.

$WDPLQLPXPDSURSDQHHQJLQHIXHOV\VWHPWHFKQLFLDQVKRXOGKDYHDYDLODEOH

*RRGTXDOLW\OLTXLGOOHGRUVQXEEHUSURWHFWHGSUHVVXUHJDXJHVLQWKHUDQJHVRI a. 05 psi. b. 015 psi. c. 030 psi. d. 0200 (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.

$YHJDVH[KDXVWJDVDQDO\]HU

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.

7KHNLWFRQWDLQVWKHIROORZLQJ 0200 PSI gauge For measuring fuel container

pressure or (on dual fuel systems) to measure gasoline fuel system pressure.

05 PSI Gauge For measuring IMPCO pressure regulator, primary pressure.

010" H2O column gauge For measuring IMPCO pressure regulator, secondary pressure.

G22 lever gauge For correct adjustment of the IMPCO pressure regulator, secondary lever.

$VVRUWHGWWLQJVKRVHDQGLQVWUXFWLRQV

Gas Exhaust Gas Analyzer

,03&2UHFRPPHQGVWKHXVHRIDYHJDVH[KDXVWJDVanalyzer (such as the Infrared Industries FGA-5000).

40

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. $LUFOHDQHUOWHULQWHUORFN

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.

,QWHUQDOHQJLQHPHFKDQLFDOIDXOWZKLFKZRXOGLQFOXGHEXWQRWEHOLPLWHGWR a. Head gasket failure. b. Improperly installed or failed timing chain. c. Excessive engine wear. d. Low or erratic compression.

Erratic engine operation or complete HQJLQHVKXWGRZQPD\UHVXOWIURP 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.

41


For example, the picture to the right was taken of an irrigation engine reported by the customer to have a propane fuel-related fault. Upon further investigation, LWZDVIRXQGWKDWHOGPLFHJQDZLQJRQthe engines 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.

Its 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. /RZFRRODQWOHYHOEORFNDJHRIFRRODQWRZ 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, %(&(57$,17+$71. 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.

42

4.0

PERFORM INSPECTIONS AND TESTS TO DETERMINE THE OPERATING CONDITION OF PROPANE FUEL-SYSTEM COMPONENTS

Take these steps before proceeding with disassembly, internal LQVSHFWLRQRUVHUYLFLQJDQ\SURSDQHIXHOV\VWHPFRPSRQHQW1. 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. &KHFNYDFXXPKRVHDQGWWLQJVRQWKHORFNRIIDQGRQWKHFDUEXUHWRUWKURWWOHERG\5HSODFHDQ\FUDFNHGRUEURNHQWWLQJV5HSODFHDQ\KRVHWKDWLVEXUQHGFUDFNHG oil-soaked, or otherwise damaged.

b. With the engine operating under load, inspect the lock-off. If the lock-off body is cold,

IURVW\RULVVZHDWLQJFOHDQRUUHSODFHWKHOWHUHOHPHQW

43


)LOWHU,GHQWLFDWLRQDQGReplacement

a. 7KHOWHUVKRZQDWULJKWUHVHPEOHVa compressed cotton pad; its OWUDWLRQFDSDELOLWLHVDUHLQWKH ten micron range.

b. :KHQUHSODFLQJWKHOWHULQVSHFWany debris found.

c. If the debris is a reddish powder, it LQGLFDWHVUXVWLQWKHIXHOV\VWHPVXSSO\WDQNRULURQSLSLQJ&KDQJLQJWKHOWHURQFHwill usually cure this problem.

d. If the debris is a gray powder, the material may be metallic particles from the propane marketers 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 UHPHPEHUWKHUHPD\EHH[LEOHUXEEHUOLQHGKRVHVHOVHZKHUHEHVLGHVZKHUHWKHengine 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 lock-off and depress approximately 3/4 of an inch. If pressurized air (connected in place RIWKHOLTXLGSURSDQHLQOHWVXSSO\QRZRZVWKURXJKWKHXQLWWKHQWKHGLDSKUDJPLVprobably ruptured.

c. If pressurized air comes out of the vacuum port, the stem of the lip seal in the LP outlet LVZRUQH[FHVVLYHO\$QRYHUKDXORIWKHXQLWZLOOXVXDOO\[WKLVSUREOHPEXWLIWKHVWHPis 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 VSHHGRYHUIXHOLQJRUULFKQHVVLGHQWLHGE\WKHLQDELOLW\WRSURSHUO\DGMXVWWKHLGOH air-fuel mixture.

Vacuum Operated Fuel Filter/Lock-off Cutaway View

44

4.0

Electric Lock-offsAn electric lock-off is a magnetic coil (solenoid). When energized, the coil becomes an electromagnet that moves a SLVWRQRIILWVVHDWDOORZLQJIXHOWRRZ When the electrical current stops, the magnetic force acting on the piston ceases, and a spring forces the piston back down RQWKHVHDWVWRSSLQJIXHORZ

Electric lock-offs are widely used in 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. 7KHIXHOOWHUIRUWKHVW\OHRIORFN

off shown above on the left is a VSXQEHUW\SHWKDWWVLQVLGHWKHOWHUVHFWLRQRIWKHORFNRIIDQGlooks like a small ball of yarn.

b. $QH[WHUQDOUHSODFHPHQWOWHUseparate from the lock-off is used with the lock-off style shown above RQWKHULJKW7KHVHOWHUVDVVKRZQin the picture to the right, resemble the EXOEW\SHUHIULJHUDQWOWHUVXVHGLQDLUFRQGLWLRQLQJV\VWHPV

c. ,IWKHOWHUVHFWLRQLVFROGRULVVZHDWLQJGXULQJORDGHGHQJLQHRSHUDWLRQUHSODFHWKHOWHUXQLWRUOWHUPDWHULDODVQHHGHG

Two Styles of Electric Lock-offs

45


Testing an Electric Lock-offa. 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/Repaira. 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 E\DNQRZQYROWVRXUFHEXWIXHOGRHVQRWRZZKHQWKHHQJLQHLVFUDQNHGWKHactual current source (for example, an oil pressure sensor) should be checked for FXUUHQWRZXVLQJDQHOHFWULFDOPXOWLPHWHU

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 160F may condense out in a SDUDIQOLNHIRUPDQGJUDGXDOO\EXLOGXSLQIXHOV\VWHPFRPSRQHQWV

In-Line Cartridge Filter Maintenancea. Used in the vapor line to catch

any pipe scale or small particles, WKHVHOWHUVKDYHUHSODFHDEOHSDSHUOWHUFDUWULGJHV

b. 7\SLFDOO\WKHVHOWHUVDUHFKDQJHG1. 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

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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.

,QPRVWFDVHVDUVWVWDJHUHJXODWRULQVWDOOHG 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 UHGE\WKHPDQXIDFWXUHUDQGDUHWWHGZLWK 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 second-VWDJHUHJXODWRUKDVVXIFLHQW%WXKUDWLQJIRUWKHengine fuel load.

For pressure stability to the propane-air mixer, DQDOLQOLQHSUHVVXUHUHJXODWRULVLQVWDOOHGimmediately upstream of the mixer.

First-Stage Regulator (Typically Red Colored)

Second-Stage Regulator (Typically Tan, Gray, or Green)

Final Stage In-Line Regulator

47


Regulator Inspection: First and Second Stage Regulatorsa. 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 UHOLHIYDOYHLQWKHHYHQWWKDWGDPDJHRUGHEULVRQWKHLUPHWHULQJRULFHRUGLVFSUHYHQWVthe 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 manufacturers instructions and NFPA 58.

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 fuel-

mixture controller from maintaining proper air-fuel ratios.

High or low secondary pressure will result in poor control of IXHOPL[WXUHVDQGFDXVHRRGLQJVWDUYLQJVXUJLQJG\LQJDQGother operating problems.

Pressure Testing Procedure for IMPCO and Woodward Vaporizers

With the engine shut down1. 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.

Courtesy of Sherwood LPG Products

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2. Remove the 1/8-inch test port plug in the high-pressure section and install a 0- to 15-psig pressure gauge.

3. &KHFNDQGUHFRUGSUHVVXUHUHDGLQJV 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 FRPSRQHQWVVSHFLHGIRUWKHHQJLQHDQGDSSOLFDWLRQ

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 YDFXXPKRVHWWLQJVRUZLULQJVKRXOGEHcompleted 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.

)XHOOWHUHOHPHQWVVKRXOGEHUHSODFHGaccording to the manufacturers UHFRPPHQGDWLRQVRULIDQ\IXHORZUHVWULFWLRQLVREVHUYHGRUVXVSHFWHG

Trap-it-Type Fuel Filter

49


Adjust Propane Fuel-Pressure Regulators to Proper Output Setting If Appropriate

These are types of regulators a turbocharged irrigation engine supplied vapor from a SURSDQHVXSSO\WDQNPD\KDYH

$UVWVWDJHUHJXODWRUORFDWHGDWWKHsupply 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).

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.

7\SLFDOO\WKHWHFKQLFLDQLVQRWUHTXLUHGWRDGMXVWWKHSUHVVXUHRXWSXWRIWKHUVWVWDJHregulator. 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.

Cut-away View of a Sub-RegulatorCourtesy of IMPCO Technologies, Inc.

Diagram of Carburetor, Air/Fuel Ratio Controller, Pilot Regulator, and Main RegulatorDiagram Courtesy of IMPCO Technologies, Inc.

50

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, LQHIFLHQWIXHOXVDJHDQGHPLVVLRQVthat do not comply with clean air regulations.

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 manufacturers repair parts kit, and follow the manufacturers instructions.

7RROVQHHGHGIRU,03&2YDSRUL]HURYHUKDXO 6WDQGDUGDWEODGHVFUHZGULYHUPRGHOVSUH 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:

'2127DWWHPSWWRVHUYLFHWKHYDSRUL]HUIXHOOWHURUIXHOORFNRIIZLWKpressure 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.

Manufacturers Diagram of Pressure Measurements Needed for Adjustment of Sub-Regulator and Main Regulator

Diagram Courtesy of IMPCO Technologies, Inc.

51


Using an IMPCO model E as an example, the basic VWHSVRIDFRQYHUWHUUHEXLOGLQFOXGH

1. Remove the eight top cover screws. Remove the cover and set it aside.

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.

IMPCO Model E Cover

Inspect the diaphragm for damage.

Note any oil pooling.

.

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6. Remove the secondary lever fulcrum pin by UHPRYLQJWKHVFUHZLGHQWLHGLQWKHSLFWXUHWRthe right, and the retaining pin only, setting the retaining pin aside for inspection.

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.

8. Next, remove the primary plate. a. 5HPRYHWKHYHVFUHZV

shown, leaving two in place.

b. While holding the plate down (its spring-loaded), remove the two remaining screws.

The plate will retain the primary pressure diaphragm and two springs.

9. Carefully remove the primary cover. Inspect the springs for damage; then place them in a secure location. Do not modify the spring tension.

Remove this screw.

Remove this pin.

Inspect these areas for damage.

a. b.

53


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.

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.

Remove these two remaining screws.

The yellow sponge absorbs liquid fuel until it vaporizes.

Now remove the primary pin.

Carefully remove the diaphragm.

c.

b.

a.

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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. ,QVSHFWWKHHQGVRIWKHEXWWHU\VSULQJfor 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.

13. Inspect the vaporizer body. a. Inspect the vaporizer body dividers and

channels for corrosion, cuts, and cracks.

Inspect the fuelinlet for damage.

Inspect rows for corrosion or damage.

Inspect the rubber surface for damage.

c.

a.

b.

a.

High pressure tap.

Coolant drain.

55


b. Turn the body over and remove the six remaining screws. Separate the two metal body pieces and remove the rubber gasket/insulator.

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 XVDEOHQLVK

Reassembly14. 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.

Inspect for corrosion or damage.

Remove the screws.

Inspect new primary seat and sponge.

c.

b.

a.

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4.0

b. Place the vapor chamber with a new JDVNHWRYHUWKHORZHUERG\DQGQJHUstart two screws. Do not tighten the screws at this time.

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).

Insert pin, then install screw. Tighten screws.

Install these WZRVFUHZVUVW

Finger-tighten these two screws.

c.

b.

Use your thumb to hold the plate down.

57


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 SLQVKRXOGMXVWWLQWKHKRRN,IDQ\IRUFHis 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.

127(7KHDERYHSURFHGXUHDSSOLHVWRWKH,03&2PRGHO(RQO\

Complete the converter reassembly by performing the previous steps in reverse order.

Use G2-2 gauge and test lever height.

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Perform Maintenance and/or Repair Operations on Propane-Air Mixer

When service is performed on propane-air mixers and carburetor systems, the following information must be remembered and applied.

0RVWHTXLSPHQWPDQXIDFWXUHUVRIIHUJDVHRXVIXHODLUPL[HUVIRUXVHZLWK

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 PDQXIDFWXUHUVVSHFLFDWLRQVDQGDSSOLFDEOHHQYLURQPHQWDOTXDOLW\UHJXODWLRQV

In general terms, when a propane-air mixer is adjusted in open loop operation at full power (engine UDWHGVSHHGXQGHUIXOOORDGLWFDQEHDGMXVWHGIRUEHVWRSHUDWLQJOHYHOVLQWKHIROORZLQJDUHDV Power. Fuel economy. Emissions.

Continental Controls Corp. Propane-Air MixerIMPCO Technologies Propane-Air Mixer

3URSDQH 1DWXUDOJDV 'LJHVWHUJDV /DQGOOJDV

Highest

Lowest

Fuel Btu Content

59


Servicing Propane-Air Mixers

$QDLUIXHOPL[HUFRPELQHGZLWKDWKURWWOHERG\EXWWHU\YDOYHLVFDOOHGDFDUEXUHWRUassembly. 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 propane-air 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.

During normal propane fuel usage, light oil deposits may accumulate on the mixers 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 Kit7KH,03&2PL[HUFRQVLVWVRIVHYHQEDVLFSDUWV 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.

Fuel Inlet Side ViewIdle Adjustment Side View

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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 WKHVHEDVLFWRROV 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 Valve1. 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.

2. Examine the diaphragm and spring. Notice the IROORZLQJLWHPV

a. The yellow diaphragm material. b. The silver decal.

The yellow diaphragm material is the premium GLDSKUDJP7KLVPDWHULDOLVEHUJODVVUHLQIRUFHGsilicone.

IMPCO Model 425 Top View

61


3. If the diaphragm is cracked, torn, cut, or otherwise damaged, it should be repl

MaintainingRepairing PropaneStationaryEngines

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