Compression Technology and Equipment 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 Compression Technology and Equipment flashcards as text
What type of compressor is most commonly used in CNG fueling stations for achieving the high pressures required for vehicle fueling?
Answer: Reciprocating piston compressor
Reciprocating piston compressors are the industry standard for CNG stations because they can achieve the high pressures (3,600 psi) needed for vehicle fueling.
What is the standard service pressure for CNG vehicle storage cylinders in the United States?
Answer: 3,600 psi (248 bar)
3,600 psi (248 bar) is the standard service pressure for CNG vehicle cylinders in the US, as established by NFPA 52 and industry standards.
What is the primary purpose of an intercooler between compression stages in a multi-stage CNG compressor?
Answer: Cool the compressed gas to improve efficiency and protect downstream components
Intercoolers cool the compressed gas between stages, reducing the work required for subsequent compression stages and protecting valves and seals from heat damage.
In a multi-stage CNG reciprocating compressor, what happens to the gas at each successive compression stage?
Answer: Pressure progressively increases as volume decreases at each stage
Each compression stage progressively increases gas pressure while reducing volume, with the cumulative effect delivering gas at full CNG service pressure at the final stage.
What is the function of a moisture separator or coalescing filter in a CNG compression system?
Answer: Remove water vapor and entrained liquids from compressed natural gas
Moisture separators remove water vapor and liquid water from compressed gas to prevent corrosion, hydrate formation, and contamination of vehicle fuel systems.
What material are piston rings and seals in oil-free CNG compressors commonly made from?
Answer: PTFE (polytetrafluoroethylene) and carbon composites
PTFE and carbon-filled composite seals are used in oil-free CNG compressors because they are chemically resistant, maintain integrity at high pressures, and require no lubrication.
What is 'cascade storage' in a CNG fast-fill fueling station?
Answer: Multiple storage vessel banks maintained at different pressure levels to optimize vehicle fill speed and efficiency
Cascade storage uses banks of cylinders maintained at low, medium, and high pressure levels, drawing from lower-pressure banks first and topping off from high-pressure banks to maximize fill efficiency.