System Lubrication and Purging 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 System Lubrication and Purging flashcards as text
What is the main purpose of an oil cooler on a screw compressor?
Answer: To remove the heat the oil picks up from compression so it keeps the right viscosity
Screw compressors inject oil that absorbs compression heat, so the oil must be cooled to keep its viscosity and lubricating ability.
A compressor shuts down on a low oil pressure safety. What is the operator's best first action?
Answer: Find the cause, such as low oil level, a clogged filter, or a pump problem, before restarting
Low oil pressure safeties protect bearings, so the cause has to be found and fixed before the compressor runs again.
Why might a reciprocating compressor crankcase heater be used during the off cycle?
Answer: To boil off refrigerant that has migrated into the oil, preventing foaming at startup
Keeping the crankcase warm limits refrigerant dissolved in the oil, which reduces foaming and oil loss at startup.
What is the purpose of an oil filter differential pressure reading on a compressor?
Answer: It shows when the filter is getting clogged and needs to be changed
Pressure drop across the filter rises as it loads with debris, telling the operator when to change it.
When manually purging a condenser, why is it best to purge from the highest point with the condenser cooled and its liquid drained?
Answer: Noncondensables collect at the high point, and letting it sit lets the air separate out
With the condenser idle and settled, air collects at the top purge connection, so less ammonia is lost when venting.
Which statement about oil carryover in an ammonia system is correct?
Answer: Oil carried into evaporators coats heat transfer surfaces and reduces efficiency
An oil film on evaporator tubes acts as insulation, which lowers heat transfer and system capacity.
Where should a person stand when draining oil from an ammonia vessel?
Answer: In a spot with a clear escape route, wearing the required PPE, and never leaving the drain unattended
Oil draining can release ammonia, so the operator needs PPE, a clear way out, and must stay at the valve the whole time.