CRST Piping, Tubing & Brazing Techniques

Question 1

Which type of copper tubing is specifically manufactured, internally cleaned, and sealed for use in refrigeration and air conditioning systems?

Accepted Answer

ACR (Air Conditioning and Refrigeration) tubing

Answer

Type L plumbing tubing

Answer

Type M plumbing tubing

Answer

Type K plumbing tubing

Question 2

When brazing copper-to-copper refrigeration joints, which brazing alloy family is self-fluxing and most commonly used in the industry?

Accepted Answer

Silver-phosphorus-copper (BCuP) alloys

Answer

50/50 tin-lead solder

Answer

Aluminum brazing rod

Answer

Zinc-tin alloy

Question 3

What is the primary purpose of flowing dry nitrogen through refrigeration piping during the brazing process?

Accepted Answer

To prevent internal oxidation and copper oxide scale formation inside the tubing

Answer

To cool the pipe rapidly after brazing is complete

Answer

To increase the brazing temperature at the joint

Answer

To simultaneously pressure-test the joint while brazing

Question 4

What is the correct preparation sequence before brazing a refrigeration copper fitting joint?

Accepted Answer

Clean mating surfaces with emery cloth until bright, then apply flux if joining dissimilar metals

Answer

Apply refrigerant oil inside the tube end to lubricate the fit

Answer

Heat the joint first to drive off moisture, then insert the fitting

Answer

Apply water to the joint area to prevent overheating

Question 5

What minimum refrigerant velocity is generally required in vertical suction line risers to ensure adequate oil return to the compressor?

Accepted Answer

700-1,000 fpm

Answer

100-200 fpm

Answer

3,000-4,000 fpm

Answer

50-100 fpm

Question 6

Which type of joint connection is recommended for permanent refrigerant piping installations in commercial refrigeration systems?

Accepted Answer

Brazed connections

Answer

Threaded NPT connections

Answer

Compression fittings

Answer

Push-to-connect quick couplings

Question 7

When a long horizontal suction line transitions into a vertical riser, what piping configuration is recommended at the base of the riser?

Accepted Answer

Install a P-trap (inverted trap) to accumulate and batch-transport oil up the riser

Answer

Install a check valve to prevent backflow

Answer

Increase the pipe diameter by one size at the riser base

Answer

Install a Y-strainer to collect debris