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Module 2: High-Pressure NGV Components
Pressure Relief
Devices (PRDs) and
Vent Lines
PRDs Vent Lines
▪ PRDs protect cylinder from rupture during fire
▪ Must be thermally activated
▪ Can be both thermally activated, and pressure activated
▪ Vent caps required
Fuel System ▪ Allow shutoff of gas to engine in emergency
Isolation Valves 1. Fuel System Isolation Valve
✓ Technicians use to isolate cylinder(s) from the
high-pressure fuel system for
maintenance/repair of downstream components
✓ First responders use to shut off the high-
pressure fuel flow to the engine at the scene of
an accident
2. Fuel System Isolation Solenoid Valve
✓ Automatically prevents the continued flow of CNG in the event of a line
break downstream of the valve and to isolate the cylinder(s)s from the
remainder of the high-pressure fuel system
High-Pressure ▪ Removes liquid or aerosol
Coalescing Filter o Oil or water
▪ Remove particulates from gas
▪ CAUTION: The high-pressure coalescing filter is ALWAYS
under high pressure.
▪ Follow manufactrer’s procedures for maintenance
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