Vacuum Integrity Test Results
Pressure Increase Over Eight-
Hour Period
Remedy
Less than 20 psi (138 kPa)
None – Tank is normal
20 to 50 psi (138 to 345 kPa)
Monitor tank and test vacuum integrity again at next maintenance date
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
47–05 CNG Fuel System
Inspecting
WARNING
Natural gas is highly flammable. See the safety
precautions listed in Chapter 16 of the
Business
Class® M2 Driver’s Manual
or
Group 47
of the
Business Class® M2 Workshop Manual
. Failure to
observe these precautions could lead to the igni-
tion of the natural gas, which could cause serious
bodily injury or death.
The following inspections must be performed by a
qualified technician, in accordance with the manufac-
turer’s established inspection criteria.
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.
Gas detection sensors are located on the cab
overhead console and in the engine compartment
on the frontwall. The sensors are located in high
areas, where rising gas vapors will pass by or ac-
cumulate. 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.
Use a bubble solution to check for leaks while per-
forming the following inspection.
1.
Inspect the fuel cylinders for dents or other signs
of damage.
Replace any leaking fuel cylinders.
2.
Ensure that the fuel cylinders are secured within
the fuel cylinder storage box.
3.
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
NOTE: During initial pre-delivery inspection
(PDI), tighten the storage box mounting bolts
(shown in
) 180 lbf·ft (244 N·m).
4.
Inspect the fuel fill port for signs of damage or
leaks. Ensure the port dust cover and the O-ring
inside the port are both present and in good con-
dition. See
5.
Inspect the pressure gauges on the fuel box for
cracks. Ensure the indicator needles are present
and in working condition. Inspect the gauge
faces for accuracy and legibility.
6.
Ensure blue caps are present on all pressure
relief devices. Each fuel cylinder is equipped with
two caps (one on each end), which are visible on
the back of the CNG fuel cylinder storage box.
One cap is located on the pressure relief valve
on the inboard side of the CNG fuel box, next to
the fuel outlet line. Check the primary relief valve
on the inboard side of the CNG fuel box for signs
of damage or leaks.
7.
Check the following components for signs of
damage or leaks.
•
Manual fuel shutoff valve
•
Fuel cylinder shutoff valves (see
•
Coolant hoses and fittings
•
Fuel lines and fittings
Fuel
47
Business Class M2 Maintenance Manual, August 2015
47/8
Property of American Airlines
