Dual Tank LNG System Operation Manual
Dual Tank LNG System Operation Manual
Dual Tank LNG System Operation Manual
ENP-064
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Dual Tank LNG System Operation Manual
Table of Contents
Glossary ......................................................................................................................................................... 3
Proprietary Statement .................................................................................................................................. 3
Preface .......................................................................................................................................................... 4
1. Safety ........................................................................................................................................................ 5
2. 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 .................................................................................................................................. 6
Figure 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 ................................................................................................................................... 4
Table 2 Plumbing BOM ................................................................................................................................. 8
Table 3 Tank Major Components .................................................................................................................. 9
Table 4 Maintenance Schedule ................................................................................................................... 14
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Glossary
AGA
ANSI
ASM
BOM
CAN
CGA
CNG
CSA
FMM
American Gas Association
American National Standards Institute
Assembly
Bill of Materials
National Standards of Canada
Compressed Gas Association
Compressed Natural Gas
Canadian Standards Association
Fuel Management Module
HP
LNG
LP
NFPA
NGV
OEM
PRD
PSI
High Pressure
Liquefied Natural Gas
Low Pressure
National Fire Protection Association
Natural Gas Vehicle
Original Equipment Manufacturer
Pressure Relive Device
2
Pounds per square inch (lb./in )
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
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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
ECN# REV
BY
Dual Tank LNG System Operation Manual
DATE
DESCRIPTION
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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.
Dual Tank LNG System Operation Manual
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:
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1. A portable fire extinguisher must be installed
on the vehicle in an easily accessible location.
vehicle identifying the fuel as liquid natural gas
(LNG).
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.
Figure 1 LNG Diamond
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 the
Dual Tank LNG System Operation Manual
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
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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. 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.
1.6.4 LNG Emergency Response
6. Keep the vehicle doors open for air
circulation.
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-KPowder (PKP) extinguishers
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.
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:
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:
1. Evacuate the area.
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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
Figure 2 Dual Tank Plumbing Schematic
Table 2 Plumbing BOM, Major Components
Item
No.
Description
Item
No.
Description
1
Fill Check Valve
9
Heat Exchanger
2
3
Fuel Shutoff Valve (Red Handle)
Excess Flow Valve
10
Fuel Fitting & Dust Cap
4
5
Vapor Shutoff Valve
Pressure Control Regulator
(Economizer)
Primary Relief Valve (230 psi)
11
12
13
Automatic Fuel Shutoff Valve
Tank Pressure Gauge & Bushing
Over Pressure Regulator 30-100 psi
(Red Handle)
14
Male Vent Connector & Dust Cap
15
Vent Check Valve
6
7
8
Secondary Relief Valve (350 psi) and
Red Cap
Fuel Gauge System
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Table 3 Tank Major Components
Item
No.
Description
1
Fill Check Valve
2
Fuel Shutoff Valve (Red Handle)
3
Excess Flow Valve
4
5
6
Vapor Shutoff Valve
Pressure Control Regulator
(Economizer)
Primary Relief Valve
7
Secondary Relief Valve
8
To Fuel Gauge Sender
10
Fuel Fitting & Dust Cap
12
Line to Tank Pressure Gauge
Figure 3 Tank Detail Showing Major Components
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
Dual Tank LNG System Operation Manual
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
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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.
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.
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.
Figure 4 Evacuation Port
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 dashmounted 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.
3.7 Secondary Relief Valve (7)
3.9 Heat Exchanger (9)
A brass cryogenic relief valve, set to 1.5 times
the maximum allowable working pressure of
the tank, prevents tank failure if the primary
The LNG heat exchanger warms and thus
vaporizes the cryogenic liquid fuel for engine
use. The heat exchanger connects to the engine
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cooling system water jacket via flexible lines,
and is mounted near the LNG tank.
Figure 7 Mechanical Tank Pressure Gauge
3.13 Over Pressure Regulator (13)
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.
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 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.
3.11 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.
Figure 8 Over Pressure Regulator
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
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.
Figure 9 Fuel Tank Vent Connector
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4. System Operation & Fueling
WARNING: The primary hazard of
leaking natural gas is flammability. If the airgas 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 startup 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.
Dual Tank LNG System Operation Manual
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 overfilling.
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.
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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.
Dual Tank LNG System Operation Manual
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.
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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
Monthly
inspection
Pressure rise
Annually
test
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
Dual Tank LNG System Operation Manual
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 vehicleside 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 defectopen 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
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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
Dual Tank LNG System Operation Manual
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 Orings, 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.
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Dual Tank LNG System Operation Manual
5. If this does not stop the leak,
depressurize the system again and call
Agility Fuel Systems support at 1-949267-7745.
Refer to the callout numbers in Figure 10.
5.6 Depressurizing an LNG System
1. Turn the ignition off and ground the
chassis.
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.
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.
5.7 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 (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.
Dual Tank LNG System Operation Manual
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
12
Line to Tank Pressure Gauge
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