Inspecting the Plumbing Components

p3 mm 47.05.000

Warning: As with all pressure vessels, CNG/LNG storage and fuel delivery systems are inherently dangerous 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 performed 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.

The following inspections must be performed by a qualified technician, in accordance with the manufacturer's established inspection criteria.

All tank components should be allowed to defrost before conducting the following inspections.

Notice: Do not use a high-pressure washer or steam cleaner on natural gas fuel system plumbing components, as this can introduce moisture and contaminants into the threads of the fittings and damage 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 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.

See Fig. for plumbing component locations.

Use a bubble solution to check for leaks while performing the following visual inspection.

  1. Pressure Control Regulator

  2. Vapor Shutoff Valve

  3. Fuel Fill Hose

  4. Secondary Relief Valve (red cap)

  5. Fuel Fill Fitting

  6. Fuel Level Sender Box

  7. Primary Relief Valve

  8. Tank Pressure Gauge

  9. Fill Vent Fitting

  10. Excess Flow Valve

  11. Fuel Shutoff Valve (liquid)

  12. Fill Check Valve

Fig. 1, LNG Tank Plumbing Components

  1. Check the following components for signs of damage or leaks.

    • Pressure control regulator

    • Vapor shutoff valve

    • Secondary relief valve

    • Primary relief valve and threaded connections

    • Excess flow valve

    • Fuel shutoff valve

    • Fill check valve

  2. Inspect the fuel fill line for signs of damage, kinked or crushed piping, or chafing.
  3. Ensure the red cap is present on the secondary relief valve.
  4. Inspect the fuel tank pressure gauge for cracks in the sight glass. Ensure the indicator needle is present and in working condition. Inspect the gauge face for accuracy and legibility.
  5. Inspect all vent lines for kinks, and signs of leaks or damage.
  6. Replace leaking or damaged fuel lines. Repair or replace leaking or damaged fittings.
Note:
Parent topic: Inspecting the LNG Fuel System
Document Number: 0000116617
Manual Publication Date: 2024-05-15
Topic Publication Date: 2024-11-22