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
In an oil-flooded rotary screw compressor, what is one of the main functions of the injected oil besides lubrication?
Answer: Sealing clearances between rotors and removing heat of compression
Injected oil seals rotor clearances, cools the compressed gas, and lubricates bearings in a flooded screw compressor.
What component typically controls capacity on most industrial rotary screw compressors?
Answer: A slide valve that changes the effective rotor length used for compression
The slide valve moves to return part of the suction gas before compression, reducing capacity on a screw compressor.
Why is a screw compressor normally started with the slide valve at the minimum-load position?
Answer: To reduce starting torque and motor inrush load
Starting unloaded reduces the torque the motor must develop, limiting starting current and mechanical stress.
On a screw compressor, the volume index (Vi) should ideally be matched to what?
Answer: The system's operating compression ratio
A Vi matched to the actual pressure ratio avoids over- or under-compression losses and improves efficiency.
An operator sees the oil separator level on a screw package steadily dropping while the compressor runs. What is the most likely cause?
Answer: Oil carryover into the system due to a faulty coalescing element or high liquid level
Steady oil loss usually means oil is passing out with discharge gas because of failed coalescers or separator problems.
What is the purpose of the oil filter differential pressure reading on a screw compressor?
Answer: To indicate when the filter is clogged and needs replacement
A rising pressure drop across the oil filter shows the element is loading with contaminants and should be changed.
A high discharge temperature alarm on an oil-injected screw compressor is most likely caused by which condition?
Answer: Insufficient oil cooling or reduced oil flow
Oil removes heat of compression, so inadequate oil cooling or flow allows discharge temperature to climb.