FREE CARO System Lubrication and Purging Questions and Answers

Question 1

An operator in an ammonia refrigeration facility notices that the compressor discharge pressure is consistently higher than normal, even on cool days.
The condenser fans are operating correctly and the coils are clean.
What is the most likely cause of this issue?

Accepted Answer

The presence of non-condensable gases in the condenser.

Answer

Overcharge of refrigerant in the system.

Answer

Excessive oil level in the compressor crankcase.

Answer

A malfunctioning expansion valve.

Question 2

What is the primary purpose of an oil separator in a large industrial refrigeration system?

Accepted Answer

To remove entrained lubricating oil from the hot discharge refrigerant vapor and return it to the compressor.

Answer

To filter out contaminants and moisture from the lubricating oil.

Answer

To cool the oil before it is reinjected into the compressor.

Answer

To provide a storage reservoir for adding new oil to the system.

Question 3

During a routine check, an operator needs to add oil to a screw compressor that is currently in operation. Which of the following describes the safest and most appropriate general procedure?

Accepted Answer

Use the pressure differential between the oil reservoir and the compressor's low-pressure side to draw oil into the system.

Answer

Shut down the compressor, vent the crankcase to atmospheric pressure, and pour oil in through the fill port.

Answer

Connect an oil pump to the oil charging valve and pump oil in until the sight glass is full, regardless of system pressure.

Answer

Slowly pour oil directly into the suction line to be carried into the compressor.

Question 4

Which of the following is a direct consequence of oil accumulating on the heat transfer surfaces of an evaporator?

Accepted Answer

A reduction in the system's cooling capacity.

Answer

Increased compressor discharge temperature.

Answer

A significant drop in condenser pressure.

Answer

The compressor will short cycle on the high-pressure control.

Question 5

When manually purging non-condensable gases from an ammonia system, an operator connects a hose from a purge valve on the high-pressure receiver to a bucket of water. What is the visual indicator that mostly non-condensable gas, rather than ammonia, is being vented?

Accepted Answer

A continuous stream of bubbles rises to the surface of the water.

Answer

The water in the bucket begins to freeze rapidly.

Answer

The water level in the bucket rises quickly.

Answer

The water turns a milky white color.

Question 6

An operator is tasked with draining oil from a dedicated collection point (oil pot) on the low-pressure side of an ammonia system. After properly isolating the oil pot, what is the next critical step before opening the drain valve?

Accepted Answer

Gently warm the oil pot to boil off any trapped liquid refrigerant.

Answer

Pressurize the oil pot with high-pressure gas to force the oil out quickly.

Answer

Heat the oil pot with a torch to lower the oil's viscosity.

Answer

Immediately connect a drain hose and open the valve.

An operator in an ammonia refrigeration facility notices that the compressor discharge pressure is consistently higher than normal, even on cool days.The condenser fans are operating correctly and the coils are clean.What is the most likely cause of this issue?

An operator in an ammonia refrigeration facility notices that the compressor discharge pressure is consistently higher than normal, even on cool days.
The condenser fans are operating correctly and the coils are clean.
What is the most likely cause of this issue?