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
Before opening a compressor for maintenance on an ammonia system, which step must be completed first?
Answer: Isolate, lock out/tag out, and pump down or evacuate the compressor to a safe pressure
Lockout/tagout plus isolation and pump-down ensure no energy or refrigerant is present before opening the compressor.
Worn or broken suction valves on a reciprocating compressor most commonly produce which symptom?
Answer: Higher than normal suction pressure with reduced capacity
Leaking suction valves let gas flow back to suction, raising suction pressure and lowering pumping capacity.
What is a typical sign of a leaking discharge valve on a reciprocating compressor?
Answer: Unusually hot cylinder head and reduced capacity as hot gas re-expands into the cylinder
Hot discharge gas leaking back into the cylinder is recompressed repeatedly, overheating the head and cutting capacity.
When adding oil to an operating ammonia compressor, why must the oil be the type specified by the manufacturer?
Answer: Incorrect oil can have improper viscosity or compatibility, causing poor lubrication, carbon, or sludge
Using the wrong oil can cause poor lubrication, varnish, or incompatibility with the refrigerant, damaging the compressor.
Why is oil drained from low points such as the bottom of ammonia evaporators and receivers, rather than returned automatically like in halocarbon systems?
Answer: Mineral oil is heavier than and not miscible with liquid ammonia, so it settles at low points
Common mineral oils are denser than and largely immiscible with ammonia, so they collect at low points and must be drained.
An operator records that compressor motor amperage has gradually increased over several weeks while suction and discharge pressures are unchanged. What might this indicate?
Answer: Mechanical wear or friction such as failing bearings
Rising amps without a change in load conditions suggests added mechanical friction, such as worn bearings or misalignment.
What is the main reason for checking coupling alignment between a compressor and its motor?
Answer: To prevent vibration, bearing wear, and seal failure
Misalignment causes vibration and side loads that wear bearings, couplings, and shaft seals prematurely.