Vacuum Integrity Test Results
Pressure Increase Over Eight-
Hour Period
Remedy
More than 50 psi (345 kPa)
Remove vehicle from service and evacuate the tank per the tank manufacturer’s
instructions
Table 1, Vacuum Integrity Test Results
47–06 CNG Fuel System
Inspecting
WARNING
As with all pressure vessels, CNG/LNG storage
and fuel delivery systems are inherently danger-
ous and should be treated as such. Beyond the
visual inspections listed below, all maintenance
and repairs to compressed natural gas (CNG) or
liquified natural gas (LNG) systems should be per-
formed by trained personnel. Individuals who are
not trained in all aspects concerning CNG/ LNG
fuel delivery systems are not permitted to service,
maintain, test, or inspect a system in any way.
Failure to comply with safety regulations may lead
to fire or explosion, resulting in property damage,
personal injury, or death.
NOTICE
Do not use a high-pressure washer or steam
cleaner on natural gas fuel system plumbing com-
ponents, as this can introduce moisture and con-
taminants into the threads of the fittings and dam-
age the sealants. It can also harm the integrity of
the CNG tank, and can cause premature failure of
the pressure relief devices (PRDs) causing loss of
CNG.
Gas detection sensors are located on the cab
overhead console, the sleeper, and in the engine
compartment on the frontwall. The sensors are
located in high areas, where rising gas vapors will
pass by or accumulate. Do not use a high-
pressure washer, steam cleaner, or silicone-based
chemicals on the gas detection sensors, as this
may permanently disable the sensors. When
cleaning the vehicle, cover the sensors with a
plastic covering. Keep the sensors covered until
the area has been cleared of any cleaning fumes.
Harsh chemicals and extremely high temperatures
may damage the sensor.
IMPORTANT: Use an approved NG leak check-
ing solution while preforming the following in-
spection.
For Fuel Managements System inspections refer to
the suppliers procedures and best practices. These
below should be competed in accordance with FMS
inspections.
1.
Ensure that the fuel cylinder storage box is se-
cured to the frame. Inspect for any signs of
looseness. If necessary, tighten the storage box
mounting bolts 160 lbf·ft (217 N·m). See
Fig. 7
.
If necessary, tighten frame-rail-mounted tank
mounting nuts and bolts as follows. See
Fig. 8
.
•
Tank mounting bracket to frame rail nuts
and bolts, 130 lbf·ft (176 N·m)
•
Top plate bolts, 160 lbf·ft (217 N·m)
•
Gusset bolts, 160 lbf·ft (217 N·m)
NOTE: During initial pre-delivery inspection
(PDI), tighten the storage box mounting bolts
(shown in
Fig. 7
) 180 lbf·ft (244 N·m).
2.
Inspect the fuel fill port for signs of damage, oil
residue, or leaks. Ensure the port dust cover and
the O-ring inside the port are both present and in
good condition. See
Fig. 9
and
Fig. 10
.
3.
Ensure that caps are present on all pressure re-
lief devices.
4.
Check the following components for signs of
damage or leaks.
•
Manual fuel shutoff valve
•
Coolant hoses and fittings
•
Fuel lines and fittings along the frame rails
to the low pressure filters and going in to
the engine
•
All fittings, connections, and joints
Fuel
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Cascadia Maintenance Manual, August 2015
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