FREE CARO Compressor Operations and Maintenance Questions and Answers

Question 1

An operator at a cold storage facility notices violent foaming in the compressor's oil sight glass immediately upon startup.
This phenomenon quickly subsides.
What is the most likely cause of this event?

Accepted Answer

Refrigerant migration into the crankcase during the off-cycle.

Answer

Excessive superheat at the compressor suction.

Answer

A malfunctioning high-pressure cut-out switch.

Answer

Non-condensables present in the refrigeration system.

Question 2

What is the primary function of a slide valve in a large screw compressor?

Accepted Answer

To provide a means of capacity control.

Answer

To filter the compressor lubricating oil.

Answer

To separate oil from the refrigerant gas.

Answer

To regulate the motor's starting amperage.

Question 3

An operator hears a loud, rhythmic knocking sound from a reciprocating compressor and observes frost on the crankcase. Which of the following is the most probable and dangerous condition occurring?

Accepted Answer

Liquid refrigerant slugging.

Answer

Oil pump cavitation.

Answer

Excessive discharge superheat.

Answer

Worn piston rings.

Question 4

Which of the following conditions is a common cause of compressor short cycling?

Accepted Answer

A dirty and clogged condenser coil.

Answer

An oversized evaporator fan motor.

Answer

A slightly undersized expansion valve.

Answer

Low ambient temperature conditions.

Question 5

The purpose of using unloaders on a multi-cylinder reciprocating compressor is to:

Accepted Answer

Reduce the starting torque and provide capacity control.

Answer

Increase the compression ratio during high load.

Answer

Ensure proper oil return to the crankcase.

Answer

Prevent oil from leaving the compressor.

Question 6

When performing a daily log check on an operating refrigeration compressor, which of the following is MOST critical to record and monitor?

Accepted Answer

Operating pressures, temperatures, and oil level.

Answer

The brand and model number of the compressor.

Answer

The ambient air temperature of the machinery room.

Answer

The date of the last refrigerant filter-drier change.

An operator at a cold storage facility notices violent foaming in the compressor's oil sight glass immediately upon startup.This phenomenon quickly subsides.What is the most likely cause of this event?

An operator at a cold storage facility notices violent foaming in the compressor's oil sight glass immediately upon startup.
This phenomenon quickly subsides.
What is the most likely cause of this event?