Compressed Natural Gas (CNG) Vehicles Flashcards
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Read the first 7 Compressed Natural Gas (CNG) Vehicles flashcards as text
What is the typical service pressure of a CNG fuel storage cylinder in a light-duty vehicle?
Answer: 3,600 psi
Light-duty CNG cylinders are commonly rated for a service pressure of 3,600 psi (about 248 bar).
Which component reduces high cylinder pressure to a usable pressure before the gas reaches the engine?
Answer: Fuel pressure regulator
A CNG pressure regulator (sometimes multi-stage) steps the high storage pressure down to injection pressure.
A CNG cylinder has an expiration date stamped on it. Why must it be removed from service when expired?
Answer: The composite or steel structure can fatigue and fail under pressure over time
CNG cylinders have a finite service life because pressure cycling and material aging can compromise structural integrity.
What odorant is added to CNG so leaks can be detected by smell?
Answer: Mercaptan
Mercaptan gives natural gas its characteristic 'rotten egg' odor for leak detection.
Where does CNG tend to accumulate if it leaks inside an enclosed space?
Answer: Near the ceiling, because it is lighter than air
CNG (methane) is lighter than air, so it rises and collects at the highest points.
Which device on a CNG cylinder vents gas to prevent rupture if the tank is exposed to fire?
Answer: Pressure relief device (PRD)
A thermally activated pressure relief device releases gas safely when exposed to excessive heat.
Before servicing the CNG fuel system, what is the correct first step?
Answer: Isolate the cylinder valve(s) and depressurize/purge the lines
The fuel system must be isolated and depressurized to safely work on high-pressure CNG components.