2ND 15

Question 1

List four types of compressors. Which is most common?
1. Axial

2. Centrifugal
3. Reciprocating
4. Rotary

Answer 1

3. Reciprocating.

Question 2

What is the purpose of the intercooler on a two-stage compressor?

Answer 2

The purpose of the intercooler on a two-stage compressor is to reduce the air intake temperatures between the low and high cylinders, and removes any condensation.

Question 3

What is the purpose of the aftercooler?

Answer 3

The purpose of the aftercooler is to remove the condensed water and oil from the air

Question 4

Why is the air receiver required on most compressor installations?

Answer 4

Air receivers are required on most compressors because it acts as a storage reservoir, to provide reserve capacity and smooth out pumping pressure pulsations. It also allows the compressor to remain idle yet have continual supply of air.

Question 5

List the essential parts of a compression refrigeration system.

Answer 5

There are five essential parts of a compression refrigeration system. They are:

1. Evaporator
2. Compressor
3. Condenser
4. Receiver
5. Expansion Valve

Question 6

What type of vacuum pump is best suited for very high vacuums?

Answer 6

The best suited vacuum pump for high vacuums is a special rotary pump with close clearances and oil seals

Question 7

How is the efficiency of a compressor affected by the intake air temperature?

Answer 7

The air supply to a compressor should be at as low of a temperature as can readily be obtained. For every 5° lower intake air temperature, the gain in efficiency is approximately 1%.

Question 8

Why are most compressors equipped with unloading valves?

Answer 8

Most compressors are equipped with unloading valves because the air flowing into and out of the cylinders during unloaded periods, helps to cool them, putting less strain on both motors and generators.

Question 9

List six possible causes for a compressor overheating.

Answer 9

Six possible causes for a compressor overheating are:

1. Broken valve strips
2. Wrong direction of rotation
3. Filter clogged
4. Discharge pressure higher than rated
5. Internal leakage
6. Insufficient oil

Question 10

What type of cleaner should be used to clean intake filters? Why?

Answer 10

Intake filters should be cleaned with hot water or steam, or immerse them in a string solution of salt soda. Never use gasoline or kerosene because the explosive fumes may collect in the compressor or air receiver.