Dual Tank LNG System Operation Manual ENP-064 Rev. C: July ...

Dual Tank LNG System Operation Manual

ENP-064

Rev. C: July 2017

ENP-064: Dual Tank LNG System Operation Manual (Printed Copy is Not Controlled) 2 of 33

Table of Contents

1. Safety..................................................................................................................................... 6

1.1 Qualified Personnel .............................................................................................................. 6

1.2 Safety Equipment ................................................................................................................. 6

1.3 General Safety Precautions ................................................................................................. 6

1.4 Natural Gas Vehicle Safety Precautions ............................................................................... 7

1.5 Welding & Hot Work Precautions ......................................................................................... 7

1.6 Codes and Compliances ...................................................................................................... 8

1.7 First Responder Guide ......................................................................................................... 8

2. System Schematics and General Assemblies .......................................................................11

3. LNG Fuel System Components .............................................................................................13

3.1 Fill Check Valve ..................................................................................................................13

3.2 Fuel Shutoff Valve (Red Handle) .........................................................................................13

3.3 Excess Flow Valve ..............................................................................................................13

3.4 Vapor Shutoff Valve (Gray Handle) .....................................................................................13

3.5 Pressure Control Regulator .................................................................................................13

3.6 Primary Relief Valve ............................................................................................................14

3.7 Secondary Relief Valve .......................................................................................................14

3.8 The Evacuation Port ............................................................................................................14

3.9 Fuel Gauge System ............................................................................................................14

3.10 Heat Exchanger ................................................................................................................14

3.11 Fuel Fitting ........................................................................................................................15

3.12 Automatic Fuel Shutoff Valve ............................................................................................16

3.13 Tank Pressure Gauge .......................................................................................................16

3.14 Over Pressure Regulator ...................................................................................................16

3.15 Vent Connector .................................................................................................................16

4. Methane Detection System ...................................................................................................16

4.1 Notes for California Vehicles Only .......................................................................................16

4.2 Test Procedure Notes – California Only ..............................................................................18

4.3 Test Procedure Notes – Non-California ...............................................................................21

5. LNG System Fueling and Engine Starting .............................................................................22

5.1 Fueling ................................................................................................................................22

5.2 Starting the Vehicle .............................................................................................................23

6. General LNG System Testing & Maintenance .......................................................................24


6.1 Maintenance Schedule ........................................................................................................25

6.2 Vacuum Loss ......................................................................................................................26

6.3 Pressure Rise Test ..............................................................................................................26

6.4 Fuel Gauge System Testing ................................................................................................26

6.5. Leak Testing ......................................................................................................................27

6.6. Flammable Gas Detectors ..................................................................................................28

6.7 Repairing Leaks ..................................................................................................................28

7. Depressurizing an LNG System ............................................................................................28

7.1 Re-Pressurizing an LNG System .........................................................................................29

8. LNG Tank De-Fueling ...........................................................................................................29

9. Appendix I: California Exemption Letter for LNG Systems .....................................................30


I. Proprietary Statement

The information provided within this manual is proprietary and confidential. All prior versions of this manual, including updates and revisions forwarded separately, are proprietary. The information provided by Agility Fuel Solutions (Agility) to its customers and clients is solely for the use of those customers and clients. No portion of this manual may be reproduced or distributed without express written consent from Agility. Agility reserves the right to utilize the intellectual property contained within this publication as content for any other Agility publication.

Portions of this manual were drawn from information provided by suppliers of Agility Fuel Solutions and used with permission.

Agility gives express consent to authorized dealers to utilize portions of this manual, or the manual in its entirety for the purposes of providing customers and clients of Agility with information pertaining to its compressed natural gas (CNG) fuel storage system with appropriate acknowledgement of copyright.

Trademark Notice

Agility® and TUFFSHELL® are registered trademarks of Agility Fuel Solutions. Drop-N-Go™ is a trademark of Agility Fuel Solutions. Trademarks of other manufacturers are the property of their respective companies.

II. Preface

This manual is designed as a supporting document to mechanics and operators trained in the operation and maintenance of liquefied natural gas (LNG) fuel systems by Agility.

No attempt should be made to fill, install, or maintain systems until this manual and all referenced supporting documentation have been read and fully understood.

III. Warning Statements Used in this Manual

Personal injury or death will occur if procedures are not followed.

Personal injury or death may occur if procedures are not followed.

Damage to equipment, fuel system or vehicle is possible if instructions are not followed.

Best practices or hints to help an operation or procedure go smoothly.


IV. Obtaining Product Support, Service or Parts

Fuel system in- or out- of warranty product support can be obtained by calling the Agility Fuel Solutions Customer Care Hotline at 949-267-7745 or toll free: 855-500-2445.

Customer Care: [email protected]

Parts: [email protected]

Visit our website for more information, including CNG and LNG fuel system videos. Go to www.agilityfuelsolutions.com

Agility Fuel Solutions | 3335 Susan St Suite 100 | Costa Mesa, CA 92677

REVISION DESCRIPTION AUTHOR APPROVED

BY DATE

-- Initial Release W. Yoshida Y. Coy 5/13/13

A Clarified fuel requirements, Sect. 4.2.1 based on ECN 10131

W. Yoshida A Bhakta 2/18/15

B

Updated company identity marks, added ANSI Z535 safety icons, updated pictures, added Calif. requirements, new cover image, re-formatted document

W. Yoshida M. Meyer 7/26/17


1. Safety

In the interest of ensuring the safety of all personnel involved with liquefied natural gas (LNG) fuel storage systems, this section outlines general guidelines that must be adhered to when operating and servicing equipment provided by Agility Fuel Solutions. Please consider the following procedures and recommendations:

1.1 Qualified Personnel

LNG systems should be maintained and inspected by trained personnel.

1.2 Safety Equipment

1. Because LNG is odorless, methane detectors must be used in the building and in the vehicle.

2. LNG safety signage should be visible at all applicable locations as stipulated by federal, state, and municipal law.

3. Natural gas rated fire extinguishers should be accessible and visible throughout all servicing and fueling areas. Be sure that fire extinguishers are charged, up to date and rated correctly.

4. Areas designated for LNG fueling systems must have adequate lighting that complies with all safety codes and standards.

5. Protective footwear and eyewear should be worn by all personnel in close proximity to a LNG system.

6. When locating the source of a leak use only certified leak detecting solutions and equipment such as FBI®, combustible gas detector, Swagelok Snoop®, Hoke Leak Detective®. Any other product or solutions are unacceptable.

7. Use tools that are in good working order with proper calibration.

8. Wear appropriate attire while servicing or maintaining any LNG system.

1.3 General Safety Precautions

1. Follow all maintenance procedures in the order in which they are written, do not skip any steps.

2. Never use an open flame as a source of illumination in proximity to a LNG system.

3. Any process or procedure that generates sparks, flames or heated particles should not be performed in areas designated for LNG.

4. LNG fuel delivery systems are to be serviced in designated areas that comply will all federal, state and municipal laws.

5. LNG servicing and fueling areas must be well ventilated as stipulated by federal, state and municipal law.

6. Perform all maintenance and service procedures in a dust free environment.


7. Never attempt to depressurize or vent a system by loosening a fitting.

1.4 Natural Gas Vehicle Safety Precautions

The following safety precautions should be considered at all times when operating natural gas fuel systems and equipment:

1. A portable fire extinguisher must be installed on the vehicle in an easily accessible location.

2. Do not start the engine if a natural gas leak is detected.

3. All systems must be grounded before transferring fuel from one vehicle to another, or during defueling. Transferring natural gas may cause a buildup of static electricity which could discharge and ignite the fuel.

4. Never attempt to open system components that are under pressure.

5. Do not smoke or produce an open flame within 30 feet of a LNG vehicle or an LNG dispensing/filling station.

1.5 Welding & Hot Work Precautions

A. Before performing any hot work procedure, make sure the fuel system is leak-free by performing a leak test with a suitable leak detection solution.

B. Before performing any welding on the vehicle chassis or body, ensure the main battery disconnect switch is turned off. Follow OEM or body builders’ manual for welding procedures.

For any welding in or near an LNG storage system, follow these additional safety recommendations:

1. Ensure the vehicle is parked in a well-ventilated area. Do not park the vehicle in an area where natural gas may accumulate.

2. If welding or hot work is performed more than six feet/two meters away from the vehicle, it is not necessary to defuel the system. However, the fuel system should be depressurized.

3. If performing hot work closer than six feet/two meters from the tanks, they must be de-fueled.

a. Cover all fuel system components, including the tank and fuel lines, with fireproof blankets or a metal shield. Isolation must prevent sparks and slag from hitting tanks and components.

b. If the tank or any components are hit by a spark or slag, the vehicle must be taken out of service and inspected.


1.6 Codes and Compliances

For more information about natural gas codes and regulations please refer to the following

USA and Canada

National Fire Protection Association, www.nfpa.org: NFPA 52

Standards Council of Canada, www.scc.ca/en: CSA B109

American National Standards Institute, www.ansi.org: ANSI/AGA NGV 3.1/CGA 12.3 and NGV 12.3-M95

International

Society of Automotive Engineers (SAE), www.sae.org: J2343

Information on Handling Cryogenic Liquids Compressed Gas Association, www.cganet.com: CGA P-12

1.7 First Responder Guide

Refer to the Agility Fuel Solutions First Responder Guide, ENP-084 for CNG and LNG firefighter first responder information.

1.7.1 Identifying an LNG Vehicle

A vehicle equipped with liquid natural gas will have a blue reflective decal on the rear of the vehicle identifying the fuel as liquid natural gas (LNG).

Figure 1 LNG diamond on an LNG-fueled bus.


1.7.2 General Information

Natural gas possesses unique hazards that are not present in gasoline or diesel fuel. Liquefied natural gas is predominantly methane (CH4) that has been converted to liquid form for storage and transport by cooling it to -260° F.

The LNG fuel tank is a cryogenic container. This means that it stores the natural gas fuel as a refrigerated liquid under pressure from about 70 psi to 230 psi.

1.7.3 LNG Hazards

Flammability

Although pure LNG is not flammable, it rapidly evaporates in air into large volumes of gas. So even small liquid leaks can pose a large fire hazard near the leak. The gas is flammable in concentrations of between 5% and 15% in air versus 1% to 99% for gasoline.

Cryogenic Temperatures

LNG is stored at -220°F to -212°F / -140°C to -136°C. Since this liquid is stored under pressure you can be cryogenically burned by a pressurized liquid stream or by touching a cryogenic fuel line.

Large Expansion Ratio

LNG expands to 600 times its original volume when warmed to a room temperature gas and will build to over 3000 psi if trapped in lines. Pressures this high may cause lines and fittings to fail. Care must be taken during maintenance operations to assure that liquid cannot become trapped between two valves.

An Inert Gas

Although natural gas is non-toxic, it is an inert gas and can cause asphyxiation if present in very large concentrations. Always keep LNG fueled vehicles in well-ventilated areas or outdoors in open air.

1.7.4 LNG Emergency Response

A. DO NOT add water to a natural gas spill. Water spray can cause LNG to violently splatter, increasing the fire danger. Allow the LNG to vaporize and dissipate into the atmosphere. Use properly rated extinguishers

B. Be especially cautious when handling an LNG leak. Cryogenic LNG can cause first degree burns and frostbite on contact. Remove sources of ignition and allow LNG to disperse into the atmosphere.


If the vehicle is damaged or a gas leak is detected:

1. Do not approach the vehicle if any sources of ignition are present, including but not limited to: fire, sparks, electrostatic charges, lights or electronic devices. Do not smoke. Do not use road flares.

2. Turn the ignition switch off, set the parking brake, and turn off the battery at the main disconnect.

3. If it is safe to do so, isolate the fuel by shutting-off the “Red Handle” valve at the end of the tank.

4. LNG is NOT odorized and CANNOT be detected by smell.

5. Make sure that traffic and pedestrians steer well clear.

6. Keep the vehicle doors open for air circulation.

7. If the vehicle is indoors, open windows and doors to allow ventilation. Avoid turning on any lights or electronics which may spark. Pay special attention to overhead ignition sources since natural gas is lighter than air and will rise.

8. Beware that gas may continue to leak even if the ignition is turned off and the manual shut-off valves are closed.

9. The leaks should be repaired by a qualified natural gas technician immediately.

1.7.5 Vehicle Fire Procedures

In the event of an LNG fire it is imperative that the vehicle operator acts quickly and efficiently by observing to the following steps:

1. Call 9-1-1.

2. Evacuate the area.

3. Get passengers out of the vehicle as quickly as possible.

4. Extinguish the fire using an appropriately rated fire extinguisher.


2. System Schematics and General Assemblies

General schematics and high level assembly drawings can be found in the section below. Drawings are intended for reference only.

Figure 2 Dual tank LNG fuel system.

ITEM DESCRIPTION

1 FILL CHECK VALVE

2 FUEL SHUTOFF VALVE (RED HANDLE)

3 EXCESS FLOW VALVE

4 VAPOR SHUTOFF VALVE

5 PRESSURE CONTROL REGULATOR (ECONOMIZER)

6 PRIMARY RELIEF VALVE (230 PSI)

7 SECONDARY RELIEF VALVE (350 PSI) AND RED CAP

8 FUEL GAUGE SYSTEM

9 HEAT EXCHANGER

10 FUEL FITTING & DUST CAP

11 AUTOMATIC FUEL SHUTOFF VALVE

12 TANK PRESSURE GAUGE & BUSHING

13 OVER PRESSURE REGULATOR 30-100 PSI

14 MALE VENT CONNECTOR & DUST CAP

15 VENT CHECK VALVE


Figure 3 Typical LNG tank valve end components.

ITEM DESCRIPTION

1 FUEL SHUTOFF VALVE (RED HANDLE)

2 VAPOR (VENT) SHUTOFF VALVE (GRAY HANDLE)

3 PRESSURE CONTROL REGULATOR (ECONOMIZER)

4 FILL CHECK VALVE

5 EXCESS FLOW VALVE 3/8-IN. NPT SS, SHROUDED TANK

6 LNG DUAL TANK 0.5 TO 4.5 FUEL LEVEL SENDER

7 PRESSURE RELIEF, VENT

8 PRESSURE GAUGE 300 PSI, 1/4 NPT (SMALL)

9 PRESSURE RELIEF, PRIMARY, 230 PSI

10a PRESSURE RELIEF, SECONDARY, 350 PSI

10b RED VINYL CAP (ON SECONDARY RELIEF VALVE)

11 NYLON RELIEF VALVE TUBE

12 NYLON ELBOW 1/2-IN. OD x 3/8-IN.

-- BLACK VINYL CAP, NOT VISIBLE

13 3/4-IN. NPT FEMALE FILL FITTING

14 FILL FITTING DUST CAP AND TETHER

15 VENT CONNECTION AND DUST CAP (1/4 TURN QD -3/8 NPT)

16 PRESSURE GAUGE 300 PSI, 1/4 NPT (LARGE)

4

5

3

9

10a/10b

12

11

13

14

8

16

7

6 15

1

2


3. LNG Fuel System Components

This section describes major system components shown in Figures 2 through 5. All figures and illustrations are intended for general reference only and do not necessarily reflect the exact configuration for any given system.

3.1 Fill Check Valve

The fill check valve prevents backflow through the fill line if a fuel coupler fails or vehicle accident occurs. It relies on tank pressure to seal and should not be regarded as a positive shutoff valve. The fill check valve connects to a top fill line inside the tank.

3.2 Fuel Shutoff Valve (Red Handle)

The fuel shutoff valve (liquid valve) provides a positive fuel line shutoff for service and maintenance. The fuel shutoff valve connects to the liquid withdrawal line at the bottom of the tank and to the vapor withdrawal line at the top of the tank through the pressure control regulator. The fuel shutoff valve is open during normal vehicle operation.

3.3 Excess Flow Valve

The excess flow valve is a specialized check valve designed to cut off fuel flow if it exceeds a certain limit. It is not a positive shutoff valve. The hard seat allows a small flow to make the valve automatically reset when the fuel shutoff valve is closed. It prevents an uncontrolled fuel release between the tank and heat exchanger if a vehicle accident occurs.

3.4 Vapor Shutoff Valve (Gray Handle)

The vapor shutoff valve (vent or vapor valve) provides a positive shutoff of the vapor withdrawal line for service and maintenance operations. The valve connects to the vapor withdrawal line at the top of the tank. The vapor shutoff valve is closed for normal vehicle operation.

3.5 Pressure Control Regulator

The pressure control regulator (economizer) opens at pressures above its set point (120 psi) and closes at pressures below its set point. An internal check valve in the fuel pickup line provides a two psi bias pressure to assist vapor flow. The regulator is factory-set and should not be adjusted.


3.6 Primary Relief Valve

A brass cryogenic relief valve sets the maximum allowable working pressure (MAWP) of the tank. Its function is to vent gas to the atmosphere if the tank pressure exceeds the MAWP, or relieves excess pressure caused by fuel expansion in the tank. It is connected to the top fill line and prevents over pressurizing the tank during filling operations. The primary relief valve is equipped with a vent tube adapter to vent gas to a safe location away from the vehicle.

3.7 Secondary Relief Valve

A brass cryogenic relief valve, set to 1.5 times the maximum allowable working pressure of the tank, prevents tank failure if the primary relief valve or line fails. It is connected to the vapor withdrawal line and provides a secondary relief path for the tank. A red vinyl cap protects the valve from debris entry and damage. If the red cap is missing, the vehicle should be immediately removed from service and the primary and secondary relief system should be inspected.

3.8 The Evacuation Port

Located on the non-plumbing head of the tank, the evacuation port provides a re-sealable connection for tank evacuation. Its secondary function is to provide a pressure relief path for leaks in the vacuum space. The evacuation port plug should not be removed, since it will cause the tank to lose vacuum, and will void your warranty.

3.9 Fuel Gauge System

The LNG system comes with an electronic fuel gauge, consisting of an in-tank level probe, a sender unit mounted on the tank and a dash-mounted gauge. The sender is a solid state, sealed unit and no adjustments are possible. It has an accuracy of ± 1/16th of a tank. Note: The fuel gauge is calibrated as a system and must be replaced with identical parts to maintain accuracy.

3.10 Heat Exchanger

The heat exchanger connects to the engine block cooling system and is mounted near the LNG tank. The heat exchanger warms the cryogenic liquid fuel, converting it into a gaseous state. This conversion also increases pressure and pushes the fuel to the engine. This is a passive system, no pumps are required. Two configurations are common, as shown in Figures 4 and 5.


Figure 4 A chassis-mounted, remote heat exchanger uses engine coolant to warm the cryogenic fuel, converting the liquid to a gas, and increases pressure to push the fuel to

the engine.

Figure 5 Some LNG systems have a U-shaped heat exchanger mounted on the valve side of the LNG tank.

3.11 Fuel Fitting

The fuel fitting connects to the re-fueling station and enables cryogenic pressure transfer. The fitting incorporates a positive shutoff device to prevent fuel leakage when disconnected. Fuel fittings include a dust cap to prevent water or debris from entering the fuel tank and system.


3.12 Automatic Fuel Shutoff Valve

The automatic fuel shutoff (solenoid) valve cuts the fuel flow to the engine when the ignition is switched off or when activated by an out of limit sensor. It is designed to protect piping downstream (warm gas side) of the heat exchanger.

3.13 Tank Pressure Gauge

A mechanical pressure gauge is located on the primary relief valve tee at the 12 o’clock position on the plumbing manifold.

3.14 Over Pressure Regulator

Some natural gas engines must operate at pressure ranges below the maximum allowable working pressure of the fuel tank. Fuel systems for these engines must include an overpressure regulator in addition to the pressure control regulator. The over pressure regulator is set to 145 psi and is mounted in the engine fuel line downstream of the heat exchanger and automatic shutoff valve. The regulator should not be adjusted.

3.15 Vent Connector

If tank venting is required at the fueling station, a compatible vent connector should be used as shown in the system schematic. Note: A relief valve in the vent line may be necessary to prevent LNG from becoming trapped between the vapor shutoff valve and the vent connector.

4. Methane Detection System

4.1 Notes for California Vehicles Only

Liquefied natural gas (LNG) fuel system vehicles in California must comply with CA Code of Regulations (13 CCR Section 935 (b) (2)), which requires the following:

Every motor vehicle equipped with an LNG fuel system shall be equipped with a methane gas detection system which shall warn of the presence of methane in the engine compartment, driver's compartment and any passenger compartments.

At a minimum, the methane gas detection system shall provide a warning before the methane gas concentration reaches 25% of the Lower Flammability Limit. Such warning shall be plainly audible and visible to the driver before entering the driver's compartment and while seated in the normal driving position.

The gas detection system shall function continuously at all times, whether or not the engine is operating, when the vehicle is operated or parked on public roadways or other areas open to the public.


At a minimum, the gas detection system shall be tested three times per calendar year at equal intervals. The testing procedure shall simulate the same gaseous fuel and operating environment in which the vehicle is used.

Test results, validating the performance of the gas detection system within the parameters established by the component manufacturer(s), shall be maintained as a permanent part of the vehicle service history records.

In addition to the above, the California Highway Patrol will be adopting a requirement for the testing of two stages of flammability warning, the first at a range of 20 percent to 30 percent and the second stage at a range of 50 percent and 60 percent. A letter explaining these requirements is attached at the end of this document. A copy of the letter is to be carried in the vehicle and a copy is to be kept on file with the vehicle maintenance records. The letter must be presented to any inspecting officer if requested.

When properly installed, the Amerex AMGaDS III two zone system meets the requirements. For methane detector testing, the Amerex 20188 Calibration Kit may be used to comply with requirements. The Amerex 20188 Calibration Kit can be purchased from Agility or an authorized Amerex dealer or distributor.


Figure 6 The Amerex part number 20188 Calibration Kit may be used to test the methane detection system for LNG-fueled vehicles in California.

DESCRIPTION AGILITY PART

NUMBER

AMEREX CALIBRATION KIT PART NUMBER: 20188 10100033

REPLACEMENT SUPPLIES

25% LEL TEST GAS, AMEREX PART NUMBER 20165 10100034

55% LEL TEST GAS, AMEREX PART NUMBER: 20166 24101121

4.2 Test Procedure Notes – California Only

The methane detection system or components (sensors, control panel, wiring) must not be removed from the vehicle, since the methane detection system inspection and test “. . . shall simulate the same gaseous fuel and operating environment in which the vehicle is used.”

4.2.1 Sensor Inspection – Visual

1. Check each sensor membrane under the end cover to make sure it is not covered with dust, oil, grease or other debris.

2. Make sure all cables and connectors are clean and are not kinked or abraded.

3. Make sure the sensors and connecting cables are properly clipped and support the sensor securely.


4.2.2 System Test for Gas Levels – Lower Limit Testing, 25 Percent Methane

Test the two sensors with 25 percent methane gas first. When using the calibration test kit, DO NOT press the control panel “Push to Test” button.

Figure 7 Typical Zone 1 sensor location. Visible in this picture: (1) two-zone control panel, (2) warning buzzer, (3) sensor (4) alarm indicator (red light) and (5) system normal

(green light). The low temperature warning light at the bottom right is not part of the methane detection system.

1. Remove the sensor from Zone 1 (usually in the cab) from its P-clip, but leave the wire harness connected.

2. Connect the regulator to the cylinder of 25 percent methane test gas.

3. Connect the length of plastic tubing to the regulator and the other end to the gas calibration adaptor assembly.

4. Push the adaptor onto the sensor.

5. Open the valve.

6. The trace light for Zone 1 should begin to flash within about one minute.

1

2 3

5

4


Figure 8 If the TRACE light flashes when exposed to the 25 percent test gas, the system passes for the zone under test. If the trace light does not flash – replace the sensor and

repeat the test.

7. If the trace light does not flash, the sensor is defective and must be replaced.

a. Turn off the gas, remove and replace the sensor.

b. Repeat the test.

8. When the one minute test is complete, turn off the gas, remove the calibration adaptor and re-install the sensor.

Figure 9 The Zone 2 sensor is usually located in the engine compartment.

9. Repeat the test with the Zone 2 sensor. The Zone 2 sensor is usually located in the engine compartment.

4.2.3 System Test for Gas Levels – Upper Limit Testing, 55 Percent Methane

Perform steps 1 through 6 for each sensor as described above, using the 55 percent LEL test gas, and then following additional steps:

1. After five to seven more seconds, the significant light should flash and the audible alarm should sound.


2. If the Sensor Fault lights, turn off the gas, and check the wiring.

3. Turn the gas on, and repeat the test.

4. If the Sensor Fault lights, replace the sensor and repeat the test.

Figure 10 The significant LED and buzzer should turn on after a few seconds.

5. This completes the test for Zone 1.

a. Turn off the gas, remove the calibration adaptor and re-install the sensor.

6. Repeat the procedure for Zone 2.

California Highway Patrol Exception Letter

A copy of the letter (see Appendix I) is to be carried in the vehicle and a copy is to be kept on file with the vehicle maintenance records. The letter must be presented to any inspecting officer if requested.

4.3 Test Procedure Notes – Non-California

For all other vehicles, an operational check and alarm demonstration can be used, twice per year. The detector manufacturer has the following recommendations.

4.3.1 Test Sensors and Display Module Twice a Year

1. The sensors and cables should remain on the vehicle. No need to remove anything.

2. Verify the membrane at the end of the sensor is intact and not covered by dirt, oil, grease or other contaminants.

3. Cables and connectors should be clean and intact.


4. Make sure the sensor and wire harness are securely mounted.

5. To test the display module, push the test button.

6. To test a sensor, expose it to a two second stream of unburned butane from a butane cigarette lighter, and verify the display panel indicates a SIGNIFICANT alarm.

7. Repeat this test for each sensor.

5. LNG System Fueling and Engine Starting

A. If the methane air-gas ratio is between 5% and 15%, the mixture becomes flammable. Make sure adequate ventilation is provided in fueling, parking and maintenance areas to prevent flammable conditions.

B. Personal protective gear must be worn when fueling LNG systems – gloves, face shield, anti-static coat, long pants and leather boots. Check with your local authority or fuel station to comply with their requirements.

C. This section includes general guidelines for fueling passive LNG systems. Always check your local fueling station for specific instructions.

5.1 Fueling

5.1.1 Fuel Requirements

The LNG fuel tank is designed to be filled from any saturated LNG fuel source. Fuel must be delivered in saturated condition at a minimum pressure of 100 psi and a minimum temperature of -200°F for proper system performance. Filtration must be 100 microns minimum.

5.1.2 Normal Fueling

The LNG fuel tank is designed to be top filled via a single hose. A return hose is not needed to achieve a 100% fill. A ullage tank above the liquid level inside the main tank prevents over-filling.

1. Most fuel stations automatically monitor fuel pressure and flow, so the only procedure is to properly connect the anti-static line, the fuel hose and push the start button to begin fueling.

2. When the tank is full, simply remove the fueling connector, return the filling nozzle to its holder and remove the ground connector.


5.1.3 Fueling a Warm Tank

An LNG fuel tank that has been idle for two to three weeks, still has fuel, and is at its relief valve pressure is considered to be a warm tank. A warm tank must be vented to or below the fuel station delivery pressure (usually 145 psi) before filling.

If pressure is above 150 psi, the tank should be vented to no lower than 145 psi.

When the proper tank pressure is achieved, follow the fueling procedures for first/hot tank fill.

5.1.4 First Fill or Hot Tank Fill

A new LNG tank is called a hot tank. Hot tanks build pressure rapidly during fueling, so fuel must be added slowly, in 5 to 10 gallon increments. Tank pressure should be 145 psi maximum during hot tank fueling. The tank may require venting between fills to maintain proper pressure.

Check the plumbing for leaks. Drive the vehicle for 10 to 15 minutes to bring the pressure and temperature to normal levels. Re-check for leaks and fill normally.

Note: The practice of vent filling, in which the vent is connected and open during the fueling process, is not recommended.

5.1.5 Rapid Pressure Changes

There are three main causes of rapid pressure rise on LNG fuel systems.

First, overfilling a tank can cause rapid pressure changes as the fuel warms and expands or cools and contracts.

Second, fuel system leaks will reduce pressure as the fuel escapes. While small leaks can be ignored (diffusion leaks), larger leaks may become dangerous and wastes fuel.

Third, loss of vacuum reduces insulating capability of the tank, and fuel becomes more susceptible to changes in outside temperature.

A properly functioning, properly filled LNG fuel system should build less than 15 psi per day. Any system that builds more than 40 psi per day should be checked and repaired.

5.1.6 Overfilling

If the fuel tank is overfilled there will be little or no space for the fuel to expand as it picks up heat through the insulation. This is wasteful, since the excess fuel is vented to the atmosphere. The most common cause of overfilling is not shutting off a single hose fill properly.

5.2 Starting the Vehicle

Starting a natural gas vehicle requires a delay between battery power turn-on and starter motor activation.

1. Ensure the system is leak-free.


2. All fuel shut-off valves (red handle on each tank) must be OPEN.

3. Make sure the vapor (vent valve, gray handle) is CLOSED.

4. Follow the standard OEM pre-vehicle start-up procedures.

5. Start the engine.

6. If the vehicle is starting from cold, let the engine idle for five minutes. This will allow coolant to warm the fuel and ensure the low-pressure lines do not freeze.

7. On extremely cold days, allow the vehicle to idle for a longer period until the coolant temperature is high enough to warm the fuel. (The vehicle defroster/heater output will be warm.)

6. General LNG System Testing & Maintenance

Figure 11 Leak detection and repair should be part of any vehicle maintenance program.

In general, the LNG system is relatively maintenance-free, although some mechanical components (heat exchanger, solenoid valve, pressure regulator) may fail due to normal wear. Leaks may develop and should be fixed as soon as possible.

Routine inspection and maintenance of the natural gas fuel system will help maximize vehicle life.

A. System components must not be under pressure during servicing to prevent serious injury.

B. This manual is intended as a supplement to training in operation and maintenance of the LNG fuel system. Operating and servicing the LNG system must be performed by qualified personnel.


C. Replacement parts must be ordered through Agility Fuel Solutions or through an approved Agility OEM dealer. Any other parts may be unsafe and will subsequently void the warranty.

6.1 Maintenance Schedule

Item Frequency

Leak test Monthly

Component inspection Monthly

Mounting bolts and straps Monthly

Pressure rise test Annually

Figure 12 Components connected directly to the tank knuckle cannot be isolated and must be defueled before working on the system.


6.2 Vacuum Loss

Total loss of vacuum (seen as outer shell frosting) is unusual for an LNG tank. However, normal vacuum will slowly decay over time as gasses diffuse out of the tank materials. As the tank ages, pressure rise times will occur more quickly and may exceed 40 psi per day.

When vacuum loss achieves this level, the tank should be re-evacuated by a competent maintenance facility.

Note: Normal vacuum life should exceed the engine life of the vehicle. We recommend performing tank re-evacuation as part of the engine overhaul or replacement procedure.

6.3 Pressure Rise Test

To establish the pressure rise of an LNG fuel system the following test should be performed. Fill the tank to between 1/2- and 3/4-full. Drive the vehicle for about 10 minutes. Park the vehicle. After 15 minutes, record the tank pressure. After at least 8 hours, record the pressure again. Check to see that the plumbing is thawed. Compare the difference between the two measurements. This is the pressure rise for the fuel system. Typical maximum pressure rise is about one psi per hour. Higher changes may require service.

6.4 Fuel Gauge System Testing

Problems with the fuel gauge system can be diagnosed with a fuel system tester. The tester enables diagnosis of both tank-side and vehicle-side circuits.

On dual tank systems, both tanks must be connected since the connecting cable is an active part of the circuit.

The fuel system tester plugs into the Weather Pack connector in series between the fuel gauge sender and vehicle wiring harness. The tester is powered from the vehicle. Turn on the power to the gauge circuit and observe the lights on the front panel. If the gauge circuit is functioning properly, all three green LEDs will be lit and the fuel gauge will read 1/4 full.

An open or short on either the fuel tank or the vehicle wiring is indicated by flashing LEDs.

If an intermittent problem is present, wiggle the wiring and connectors and observe the LED indicators.

The fuel tank can be tested off the vehicle. Connect the tester to the 3-pin Weather Pack connector on the tank and push the test top panel button. In this mode, only one green indicator will light if the tank side wiring is functioning correctly. (Sender OK). A fault condition is indicated by either sender defect-open or sender defect shorted.


6.5. Leak Testing

Large leaks will create bubbles so quickly they may burst and dry before they can be seen. It is recommended that general leak surveys be done with an ultrasonic leak detector or flammable gas detector in addition to bubble test solutions.

System leaks usually occur at fittings and connectors and should be checked periodically. Use only certified leak detecting solutions and equipment. Any other products are unacceptable.

6.5.1 Locating Leaks

1. Apply leak detecting solution and look for bubbles or foam at the site of the leak.

2. Examine connections for ice, frost or condensation around the tubing.

3. Check for physical damage.

6.5.2 System Leaks

Leaks smaller than 100 cc per minute are best found with test solutions. Bubble testing will locate the source of small leaks.

Large leak bubbles may blow away before they can be seen, but they may be audible and should be repaired.

6.5.3 Small Flammable Leaks

Leaks between 25 cc per minute and 100 cc per minute are flammable in still air. If ignited the flame ranges from less than 1/16th of an inch to about 1 inch. This leak is characterized by bubbles that grow and burst at the site of the leak. These leaks pose no hazard in moving air, or in well ventilated compartments, but could accumulate inside small, poorly ventilated enclosed spaces. These leaks are typically caused by poor pipe support, routing or cyclic strain on joints.

6.5.4 Non Flammable Leaks

Leaks flowing at or less than 25 cc per minute are not flammable in air, but can be considered an economic nuisance. They are characterized by a stream of bubbles that grow and foam away from the leak. Typically the bubbles range from 1/8- to 3/8-inch in diameter. The largest leak in this group, 25 cc per minute, will cost a few dollars per year in lost LNG.

6.5.5 Insignificant Leaks (Diffusion)

Leaks smaller than 1/2 cc per minute are so small and diffuse so rapidly that they can be ignored. They are characterized by a series of tiny (smaller than a pinhead) bubbles or foam


emerging from the leak. This might show up immediately as foam around the leak or fitting for up to 5 minutes after the fitting is sprayed with solution. In either case the leaks are not flammable and will not accumulate in vehicle compartments.

6.6. Flammable Gas Detectors

Handheld flammable gas detectors are available in a wide variety of configurations and sensitivities. They are useful for surveying for leaks, but are not good at finding exact leak locations. A thorough inspection procedure includes the use of leak solution and electronic detectors.

6.7 Repairing Leaks

Never tighten or loosen a fitting when the system is under pressure. Always follow proper safety and service procedures when fixing a leak. Failure to follow safety standards and procedures may result in serious damage or personal injury.

6.7.1 Repairing Leaks

1. Depressurize the system.

2. Remove the fitting and clean all mating surfaces. Make sure all gaskets and O-rings, if used, are not damaged or worn. Apply nickel tape on the threads and replace/re-tighten the fittings.

3. Repressurize the system.

4. Perform a leak test.

5. If this does not stop the leak, depressurize the system again and call Agility Customer Care at 1-949-267-7745.

7. Depressurizing an LNG System

1. Turn the ignition off and ground the chassis.

2. Close the red handle shutoff valve.

3. Locate the engine low pressure filter petcock, and slowly “crack open” the handle counter-clockwise to vent the gas.

4. Turn the ignition switch to ON, but do not start the engine. This activates the solenoid valve and vents the tank.

5. The system is now depressurized and work may be performed. Note, the tank is still pressurized.


7.1 Re-Pressurizing an LNG System

1. When work is completed, repressurize the system as follows:

2. Close the engine low pressure filter petcock.

3. Leave the red handle shutoff valve open for normal operation.

8. LNG Tank De-Fueling

Figure 13 Defueling an LNG tank requires modification and special procedures.

Defueling an LNG system requires modification of plumbing components. A video of this procedure is posted on the Agility website, and a service bulletin is available for more details. (Contact Agility Customer Care for a copy of Field Service Bulletin ENP-462, “Depressurize or Defuel? Safely Working on LNG Fuel Systems.”)

1. Depressurize the system.

2. Remove the excess flow valve and the 3/8-inch line.


3. Install a 3/8-inch NPT elbow onto the fuel shutoff valve.

4. Install a length of 3/8-inch tube onto the elbow to create a temporary vent. The tubing should be long enough to safely carry vapor away.

5. Secure the tubing since there will be as much as 200 psi flowing from this tube when the venting starts.

6. Open the shutoff valve slowly and allow to drain completely.

NOTE: Although LNG is now removed, the tank may still be pressurized.

7. Connect to the station vent line

8. Open the vapor shutoff valve to remove pressure in the vapor line.

9. When work is completed, remove the temporary vent tube, re-install the excess flow valve and the line to the tank pressure gauge, and then repressurize and re-fuel the tank.

9. Appendix I: California Exemption Letter for LNG Systems

File name: CHP Exemption 7-6-09 (2) (2).pdf

A copy of the letter is to be carried in the vehicle and a copy is to be kept on file with the vehicle maintenance records. The letter must be presented to any inspecting officer upon request.

Dual Tank LNG System Operation Manual ENP-064 Rev. C: July ...

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