Dual Tank LNG System Operation Manual ENP-064 2 2
Table of Contents
Glossary ... 3 Proprietary Statement ... 3 Preface ... 4 1. Safety ... 52. System Schematics and General Assemblies ... 8
3. Fuel System Components... 9
4. System Operation & Fueling ... 12
5. General LNG System Testing & Maintenance ... 13
Figures
Figure 1 LNG Diamond ... 6Figure 2 Dual Tank Plumbing Schematic ... 8
Figure 3 Tank Detail Showing Major Components ... 9
Figure 4 Evacuation Port ... 10
Figure 5 Heat Exchanger ... 11
Figure 6 Automatic Fuel Shutoff Valve ... 11
Figure 7 Mechanical Tank Pressure Gauge ... 11
Figure 8 Overpressure Regulator ... 11
Figure 9 Fuel Tank Vent Connector ... 11
Figure 10 Tank Detail, Major Components ... 16
Tables
Table 1 Revision Level ... 4Table 2 Plumbing BOM ... 8
Table 3 Tank Major Components ... 9
Glossary
AGA American Gas Association
ANSI American National Standards Institute ASM Assembly
BOM Bill of Materials
CAN National Standards of Canada CGA Compressed Gas Association CNG Compressed Natural Gas CSA Canadian Standards Association FMM Fuel Management Module
HP High Pressure LNG Liquefied Natural Gas LP Low Pressure
NFPA National Fire Protection Association NGV Natural Gas Vehicle
OEM Original Equipment Manufacturer PRD Pressure Relive Device
PSI Pounds per square inch (lb./in2)
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 Systems 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 of Agility Fuel Systems. Agility Fuel Systems reserves the right to utilize the intellectual property contained within this publication as content for any other publication produced by Agility Fuel Systems.
Agility Fuel Systems gives express consent to our customers to utilize portions of this manual, or the manual in its entirety, for the purposes of providing their customers and clients with information pertaining to the Agility Fuel Systems liquefied natural gas (LNG) fuel storage system as used on their LNG vehicles with appropriate acknowledgement of copyright.
It should be noted that the version of this manual dated 05/06/2013 replaces any prior version. Any information reproduced by our customers for their use, or that of their customers and clients, should be drawn from this manual.
Agility Fuel Systems 1815 Carnegie Ave Santa Ana, CA 92705 USA Product Support +1-949-267-7745 support@agilityfs.com www.agilityfs.com
Dual Tank LNG System Operation Manual ENP-064 4
ENP-045 Oct 2012
Preface
This manual is designed as a supporting document to mechanics and operators trained in the operation procedures and maintenance of the liquefied natural gas (LNG) fuel system provided by Agility Fuel Systems.
No attempt shall be made to fill, install, or maintain this system until this manual and all referenced supporting documentation have been read and fully understood.
OEM Replacement parts may be obtained by contacting Agility Fuel Systems.
CAUTION:
All replacement parts must adhere to the accepted standards and ratings as specified by Agility Fuel Systems. The usage of any part that is not approved by Agility Fuel Systems is not
recommended and may compromise the integrity and safety of the system.
Do not remove components from original packaging until absolutely necessary. Any components that are to be reinstalled must be thoroughly cleaned, inspected, and stored in a satisfactory manner until reinstallation.
Table 1 Revision Level
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 Systems. Please consider the following procedures and recommendations:
1.1 Personnel
LNG systems should be maintained and inspected by trained personnel.
1.2 Safety Equipment
1. LNG safety signage should be visible at all applicable locations as stipulated by federal, state, and municipal law.
2. 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. 3. Areas designated for LNG fueling systems must have adequate lighting that complies with all safety codes and standards.
4. Protective footwear and eyewear should be worn by all personnel in close proximity to a LNG system.
5. 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.
6. Only use tools that are in good working order with proper calibration.
7. 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 steps without explicit permission to do so. 2. Never use an open flame as a source of illumination in proximity to a LNG system. Natural gas is flammable.3. Any process or procedure that generates sparks, flames, or heated particles should not be applied in areas designated for LNG. 4. If an LNG system does require a process or procedure that generates sparks, flames, or significant heat, conduct the procedure in an isolated area and make sure that the LNG system has been completely purged with an inert gas.
5. LNG fuel delivery systems are to be serviced in designated areas that comply will all federal, state, and municipal laws.
6. LNG servicing and fueling areas must be well ventilated as stipulated by federal, state, and municipal law.
7. Perform all maintenance and service procedures in a dust free environment. 8. Never attempt to depressurize or vent a system by loosening a fitting.
1.4 Natural Gas Vehicle Safety
Precautions
WARNING: Strict compliance with proper safety and handling practices is essential when operating any natural gas fuel system.
The following safety precautions should be considered at all times when operating natural gas fuel systems and equipment:
Dual Tank LNG System Operation Manual ENP-064 6 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. Ensure that all systems are 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.
7. Do not smoke or produce an open flame within 30 feet of a LNG vehicle or an LNG dispensing/filling station.
1.5 Codes and Compliances
For more information about LNG codes and regulations please refer to the following: USA
National Fire Protection Association, www.nfpa.org: NFPA 52
Canada
Standards Council of Canada, www.scc.ca/en: CSA B109
USA and Canada
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
1.6 First Responder Guide
1.6.1 Identifying a Natural Gas vehicle A vehicle equipped with liquid natural gas will have a blue reflective decal on the rear of thevehicle identifying the fuel as liquid natural gas (LNG).
Figure 1 LNG Diamond
1.6.2 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 temporarily to liquid form for ease of storage and transport by cooling it to -260° F.
This process reduces its volume by a factor of more than 600 over natural gas at zero pressure.
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 psig to 230 psig.
1.6.3 LNG Hazards Flammability
Although pure LNG is not flammable, it rapidly evaporates in air into large volumes of gas. The gas expands to 600 times its original liquid volume. 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
The liquid LNG is below -200° F. Since this liquid is stored under pressure you can be
cryogenically burned very easily by coming in contact with a pressurized liquid stream. You
can also be cryogenically burned upon contact with a cryogenic temperature fuel line. Large Expansion Ratio
Since LNG will expand to 600 times its original volume when warmed from a cryogenic liquid to a room temperature gas it will build extremely high pressures (over 3000 psig) if trapped in lines. Pressures this high will cause lines and fittings to fail. Care must be taken during maintenance operations to assure that liquid cannot become trapped between two valves.
Inert Gas
Although natural gas is non-toxic it is an inert gas and can cause asphyxiation if present in very large concentrations. This is a minimal hazard with vehicle fuel systems as they simply don’t contain enough gas to displace large quantities of oxygen around the vehicle. 1.6.4 LNG Emergency Response
WARNING: 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 dry powder or Purple-K-Powder (PKP) extinguishers
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 has sustained damage 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, electronic devices. Do not smoke or allow anyone else to smoke in the vicinity of the vehicle. Avoid using 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 located inside the “Cage” at the end of the LNG 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 sources of ignition; natural gas is lighter than air and will rise. 8. Beware that gas may continue to leak
once ignition is turned off and the manual shut-off valves are closed. 9. Check the fuel system again for leaks. 1.6.5 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:
Dual Tank LNG System Operation Manual ENP-064 8 2. Get passengers out of the vehicle as
quickly as possible.
3. Extinguish the fire using an
appropriately rated fire extinguisher. 4. If the vehicle has been subjected to a fire or collision exceeding 5 mph, the
fuel storage system must be inspected by a certified inspector before it can be returned to service
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
Table 2 Plumbing BOM, Major Components
Item
No. 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
Item
No. Description
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
(Red Handle)
14 Male Vent Connector & Dust Cap 15 Vent Check Valve
3. Fuel System Components
This section describes major system components as shown in Figures 2 and 3 and Tables 2 and 3. All figures and illustrations are intended for general reference only and do not necessarily reflect the exact configuration for any given system. Illustrations are not to scale.
3.1 Fill Check Valve (1)
A bronze swing check or swing poppet style valve with soft seat 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 (2)
The fuel shutoff valve (liquid valve) is a bronze globe type with a soft seat. It provides a
positive fuel line shutoff for service and
maintenance operations. 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 (3)
The excess flow valve is a specialized check valve with a hard metal seat designed to cut off fuel flow if it exceeds a certain limit. It is not a positive shutoff valve. The hard seat allows a
Figure 3 Tank Detail Showing Major Components
Item
No. 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 7 Secondary Relief Valve 8 To Fuel Gauge Sender 10 Fuel Fitting & Dust Cap 12 Line to Tank Pressure Gauge
Dual Tank LNG System Operation Manual ENP-064 10 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 (4)
The vapor shutoff valve (vent valve) is a bronze globe valve with a soft seat. It 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 (5)
The pressure control regulator (economizer) is a bronze pressure-reducing valve that 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 (6)
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 pipe away adapter to vent gasses to a safe location away from the vehicle.
3.7 Secondary Relief Valve (7)
A brass cryogenic relief valve, set to 1.5 times the maximum allowable working pressure of the tank, prevents tank failure if the primaryrelief 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.
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.
3.8 Fuel Gauge System (8)
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.
3.9 Heat Exchanger (9)
The LNG heat exchanger warms and thus vaporizes the cryogenic liquid fuel for engine use. The heat exchanger connects to the engine
Figure 8 Over Pressure Regulator Figure 7 Mechanical Tank Pressure Gauge
cooling system water jacket via flexible lines, and is mounted near the LNG tank.
Figure 5 Heat Exchanger
3.10 Fuel Fitting (10)
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.
3.11 Automatic Fuel Shutoff Valve
(11)
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.
3.12 Tank Pressure Gauge (12)
A mechanical pressure gauge is located on the primary relief valve tee at the 12 o’clock position on the plumbing manifold.3.13 Over Pressure Regulator (13)
Some natural gas engines must operate at pressure ranges below the MAWP of the fuel tank. Fuel systems for these engines must include an overpressure regulator in addition to the pressure control regulator. The overpressure 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.
3.14 Vent Connector (14)
If tank venting is required at the refueling 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.
Figure 6 Automatic Fuel Shutoff Valve
Dual Tank LNG System Operation Manual ENP-064 12
4. System Operation & Fueling
WARNING: The primary hazard of leaking natural gas is flammability. If the air-gas concentration reaches 5%, the mixture becomes flammable. Make sure adequate ventilation is provided in parking and maintenance areas to prevent flammable conditions.
4.1 Starting the Vehicle
Starting a natural gas vehicle requires a delay between the battery power being turned on and the starter motor being activated. 1. Ensure that the system has been properly
leak tested, this can be accomplished by following the Testing for Leaks procedure described in Section 5.2
2. Ensure that the cylinder shut-off valves (one on each cylinder) are “OPEN/ON” and the manual shut-off valve is turned to the “OPEN/ON” position.
3. Follow the standard OEM pre-vehicle start-up procedures.
4. Start the engine.
5. If the vehicle is starting from cold, let the engine idle for five minutes. This will allow coolant to warm the fuel and ensure that the low-pressure lines do not freeze. 6. 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.)
4.2 Fueling
CAUTION: This section includes general guidelines for LNG fueling. Always check your local fueling station for specific rules and regulations.
WARNING: Personal protective gear must be worn when fueling – gloves, face shield, anti-static coat, long pants and leather boots. Check with your local authority to comply with their requirements.
4.2.1 Fuel Station 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 temperature of -200°F or higher for proper system performance. Filtration must be 100 microns minimum.
4.2.2 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.
4.2.3 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.
4.2.4 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.
4.2.5 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 psig per day. Any system that builds more than 40 psig per day should be checked and repaired.
4.2.6 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 will be vented to the atmosphere. The most common cause of overfilling is not shutting off a single hose fill properly.
5. General LNG System Testing & Maintenance
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. Routine inspection and maintenance of the natural gas fuel system will help maximize vehicle life. This section is intended to be a general overview of system components. Contact Agility Fuel Systems for more detailed service and repair information.
WARNING: System components must not be under pressure during servicing to prevent serious injury.
WARNING: 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 authorized trained personnel.
Dual Tank LNG System Operation Manual ENP-064 14
CAUTION: Replacement parts must be ordered through Agility Fuel Systems or through an approved Agility OEM dealer. Any other parts may be unsafe and will
subsequently void the warranty. All replacement parts and components must receive approval from Agility Fuel Systems prior to installation.
5.1 Maintenance Schedule
Table 4 Maintenance Schedule
Item Frequency
Storage System:
Leak test Monthly
Component
inspection Monthly
Pressure rise
test Annually
5.1.2 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.
5.1.3 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.
5.1.4 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.
5.2. Leak Testing
CAUTION: 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 such as FBI®, combustible gas detector, Swagelok Snoop® or Hoke Leak Detective®. Any other products are unacceptable.
5.2.1 Locating Leaks
1. Apply leak detecting solution and look for bubbling or foaming at the site of the leak. 2. Examine connections for icing or signs of condensation around the tubing.
3. Check for physical damage.
5.3. 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.
5.3.1 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.
5.3.2 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.
5.3.3 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.
5.4. 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 leak sources. A thorough inspection procedure includes the use of leak solution and optionally, electronic detectors.
5.5. Tightening Leaky Fittings
WARNING: Never tighten 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.
5.5.1 Repairing Leaks
1. Depressurize the system as described below.
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 leak testing as described in Section 5.2.
Dual Tank LNG System Operation Manual ENP-064 16 5. If this does not stop the leak,
depressurize the system again and call Agility Fuel Systems support at 1-949-267-7745.
Refer to the callout numbers in Figure 10.
5.6 Depressurizing an LNG System
1. Turn the ignition off and ground thechassis.
2. Close the red handle shutoff valve (2). 3. Locate the engine low pressure filter
petcock, and slowly “crack open” the handle counter-clockwise to vent LNG to the atmosphere
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.
5.7 Re-Pressurizing an LNG System
1. When work is completed, repressurizethe system as follows:
2. Close the engine low pressure filter petcock.
3. Leave the red handle shutoff valve (2) open for normal operation.
5.8 LNG Tank De-Fueling
1. Depressurize the system by following Section 5.6, steps 1-5.
2. Remove the excess flow valve (3) and the 3/8-inch line (12).
3. Install a 3/8-inch NPT elbow onto the fuel shutoff valve (2).
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 (2) 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 (4) to remove pressure in the vapor line.
9. When work is completed, remove the temporary vent tube, re-install the excess flow valve (3) and the line to the tank pressure gauge (12), and then repressurize and re-fuel the tank.
Figure 10 Tank Detail, Major Components
Item
No. 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
7 Secondary Relief Valve
8 To Fuel Gauge Sender
10 Fuel Fitting & Dust Cap
