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

ACR tubing is deoxidized, internally cleaned, dehydrated, and sealed at the factory to keep the interior free of moisture and contamination for refrigerant service.

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

BCuP (silver-phosphorus-copper) alloys are self-fluxing on copper-to-copper joints because phosphorus acts as its own flux, making them the industry standard for refrigeration brazing.

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

Nitrogen purging displaces oxygen inside the tubing during heating, preventing the formation of copper oxide scale that could contaminate the refrigerant system and damage components.

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

Surfaces must be mechanically cleaned to bare, shiny metal, and appropriate flux applied when needed, to ensure proper brazing alloy flow and a leak-free joint.

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

Vertical suction line risers require approximately 700-1,000 fpm minimum velocity to carry entrained oil droplets upward against gravity back to the compressor.

(CRST) Certified Refrigeration Service Technician Practice Test

(CRST) Certified Refrigeration Service Technician Practice Test

CRST Piping, Tubing & Brazing Techniques