CRST Piping, Tubing & Brazing Techniques 2

Question 1

In refrigeration copper tubing work, what does the term 'swaging' refer to?

Accepted Answer

Expanding the end of a tube so another tube of the same diameter can be inserted for a brazed connection

Answer

Cutting tubing at an angle using a hacksaw

Answer

Bending tubing to a precise angle without a bender

Answer

Pressure-testing a completed joint with refrigerant

Question 2

In what direction should horizontal suction lines be sloped to promote oil return?

Accepted Answer

1/4 inch per foot sloping toward the compressor

Answer

Level with zero slope to minimize pressure drop

Answer

1/4 inch per foot sloping toward the evaporator

Answer

1 inch per foot sloping toward the condenser

Question 3

Which gas is the recommended medium for pressure-testing refrigerant piping after brazing is complete?

Accepted Answer

Dry nitrogen

Answer

Oxygen from a welding cylinder

Answer

The system refrigerant charge

Answer

Compressed air from a shop compressor

Question 4

Why must oxygen NEVER be used to pressure-test or purge a refrigeration system?

Accepted Answer

Oxygen combined with compressor oil under pressure creates an explosive mixture capable of detonation

Answer

It causes the copper tubing to turn green from oxidation

Answer

It is too costly compared to alternative gases

Answer

It reacts with the refrigerant to form a non-condensable gas

Question 5

What is the recommended minimum bend radius for ACR copper tubing to prevent kinking, flattening, or cracking during bending?

Accepted Answer

3 times the tube outside diameter

Answer

Equal to the tube outside diameter

Answer

1.5 times the tube outside diameter

Answer

8 times the tube outside diameter

Question 6

In a horizontal suction line where pipe size must be reduced, which type of reducer fitting is preferred and why?

Accepted Answer

Eccentric reducer with the flat side down, so oil can drain continuously along the pipe bottom

Answer

Concentric reducer, because it centers both pipes on the same axis

Answer

Concentric reducer, because it creates less turbulence

Answer

Eccentric reducer with the flat side up, to keep vapor at the bottom

Question 7

What is the primary purpose of vibration eliminators (flexible connectors) installed in refrigeration suction and discharge lines near the compressor?

Accepted Answer

To absorb compressor vibration and prevent metal fatigue or cracking from transmitting through the piping

Answer

To act as check valves preventing refrigerant backflow

Answer

To increase refrigerant flow velocity in the lines

Answer

To allow for seasonal thermal expansion of the piping