Compressor Operations and Maintenance Flashcards
7 cards from real CARO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Compressor Operations and Maintenance flashcards as text
A compressor's high-pressure cutout trips repeatedly. Which condition is the most likely cause?
Answer: Non-condensable gases or loss of condenser water/air flow
Non-condensables or poor condenser heat rejection raise head pressure until the high-pressure cutout opens.
What is the function of the oil pressure safety (oil failure) switch on a compressor?
Answer: Stops the compressor if net oil pressure does not reach a safe level within a set time delay
The oil failure switch shuts down the compressor when net oil pressure stays below its setpoint beyond the time delay.
Why does an oil failure switch include a time delay, often around 90-120 seconds?
Answer: To allow oil pressure to build during startup without nuisance trips
The delay gives the oil pump time to build pressure at startup so the compressor is not shut down needlessly.
What happens if a compressor short-cycles frequently?
Answer: Increased motor and contactor wear, poor oil return, and higher energy use
Frequent starts stress motors and contactors and may not allow enough run time to return oil properly.
What is the purpose of the suction strainer installed at a compressor inlet?
Answer: To trap scale, dirt, and debris before they enter the compressor
The suction strainer catches solid debris that could damage valves, pistons, or rotors.
In a two-stage ammonia compression system, what is the role of the booster compressor?
Answer: To compress gas from the low-stage suction to the intermediate pressure
The booster raises low-temperature suction gas to the intermediate pressure, where the high-stage compressor takes it to condensing pressure.
An operator observes that a compressor's discharge temperature is higher than normal while suction superheat is also very high. What is the likely cause?
Answer: Starved evaporator or underfed system producing high-superheat suction gas
High suction superheat means hot gas enters the compressor, which raises discharge temperature, often due to evaporator starvation.