Cylinder Inspection and Regulations Flashcards
7 cards from real CNG practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Cylinder Inspection and Regulations flashcards as text
What is the primary function of a thermally activated pressure relief device (PRD) on a CNG cylinder?
Answer: To release cylinder contents if exposed to extreme heat or fire, preventing catastrophic rupture
A thermally activated PRD (fusible plug) vents cylinder contents when fire or extreme heat is detected, preventing the cylinder from rupturing under thermal stress.
At what service pressure do most modern high-pressure CNG vehicle fuel systems operate?
Answer: 3,600 psi (248 bar)
Most modern CNG vehicle fuel systems operate at 3,600 psi (248 bar) service pressure, though older systems may use 3,000 psi.
What type of pressure relief device is most commonly used on CNG cylinders for combined over-pressure and fire protection?
Answer: A combination device incorporating both a rupture disc and a thermal fuse
Combination PRDs use a rupture disc for mechanical over-pressure protection and a thermal fuse for fire conditions, providing dual-mode safety coverage.
What condition found in a CNG cylinder mounting bracket requires immediate replacement before returning the vehicle to service?
Answer: The bracket has visible cracks or is missing required mounting fasteners
Cracked or incomplete mounting brackets cannot securely support the cylinder and must be replaced, as cylinder movement during operation poses a serious safety risk.
What is the correct procedure when a CNG cylinder valve is found to be leaking during inspection?
Answer: Remove the cylinder from service and have the valve repaired or replaced by a qualified technician
A leaking high-pressure CNG valve requires removing the cylinder from service; field repairs to valve components are not approved and pose serious safety risks.
What does a 'DOT-3AA' designation stamped on a CNG cylinder indicate?
Answer: A seamless steel cylinder manufactured and tested to DOT Specification 3AA
DOT-3AA designates a seamless steel pressure vessel manufactured and tested to comply with DOT Specification 3AA, which governs its construction and pressure ratings.
During inspection, what must a technician verify when examining the pressure relief device (PRD)?
Answer: The PRD is free of corrosion, rated for the correct pressure, and shows no signs of prior thermal actuation
A corroded PRD, incorrect pressure rating, or evidence of prior thermal activation are all grounds for replacement, since any of these conditions can prevent correct emergency function.