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 should an operator check FIRST if a CNG compressor fails to start?
Answer: Check electrical power supply, control circuit status, and any fault indicators on the control panel
Electrical and control system faults are the most common and easily corrected causes of compressor startup failures, making power supply and control panel diagnostics the logical first step.
What condition is most likely indicated by an abnormally high final-stage discharge temperature on a CNG compressor?
Answer: Failed or worn compressor valves, or inadequate intercooling between stages
Faulty or worn compressor valves that allow gas blow-by, or inadequate intercooling between stages, are the primary causes of excessive final discharge temperatures.
What is the purpose of an unloader valve on a CNG reciprocating compressor?
Answer: Allow the compressor motor to start without compression load before gradually applying load
Unloader valves allow the compressor motor to start without compression resistance, reducing starting current and mechanical stress, with compression load applied gradually as the motor reaches operating speed.
Which parameter is most critical to monitor continuously during CNG compressor operation to detect developing problems early?
Answer: Stage discharge pressures and temperatures at each compression stage
Monitoring stage discharge pressures and temperatures reveals compressor valve condition, intercooler effectiveness, and compression efficiency, providing early warning of developing mechanical failures.
What action should an operator take IMMEDIATELY if a CNG compressor's lubricating oil pressure drops below the minimum safe operating level?
Answer: Immediately shut down the compressor to prevent bearing and mechanical damage
Low oil pressure causes rapid bearing and crankshaft wear; immediate shutdown is mandatory to prevent catastrophic mechanical damage and potential gas release from seal failure.
What does an increasing pressure differential across a CNG compressor inlet filter indicate?
Answer: The filter is becoming clogged with contaminants and requires cleaning or replacement
A rising pressure drop across an inlet filter indicates debris accumulation that restricts gas flow, reduces compressor efficiency, and requires filter service to restore proper operation.
How frequently should compressor valve inspections typically be performed in a CNG fueling station?
Answer: Per manufacturer specifications, typically every 1,000 to 4,000 operating hours
CNG compressor valves are high-cycle wear components prone to fatigue failure; manufacturer-specified inspection intervals ensure problems are identified before unplanned shutdowns occur.