Piping, Tubing & Brazing Techniques Flashcards
7 cards from real CRST practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Piping, Tubing & Brazing Techniques flashcards as text
Which type of copper tubing is specifically manufactured, internally cleaned, and sealed for use in refrigeration and air conditioning systems?
Answer: ACR (Air Conditioning and Refrigeration) tubing
ACR tubing is deoxidized, internally cleaned, dehydrated, and sealed at the factory to keep the interior free of moisture and contamination for refrigerant service.
When brazing copper-to-copper refrigeration joints, which brazing alloy family is self-fluxing and most commonly used in the industry?
Answer: Silver-phosphorus-copper (BCuP) alloys
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.
What is the primary purpose of flowing dry nitrogen through refrigeration piping during the brazing process?
Answer: To prevent internal oxidation and copper oxide scale formation inside the tubing
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.
What is the correct preparation sequence before brazing a refrigeration copper fitting joint?
Answer: Clean mating surfaces with emery cloth until bright, then apply flux if joining dissimilar metals
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.
What minimum refrigerant velocity is generally required in vertical suction line risers to ensure adequate oil return to the compressor?
Answer: 700-1,000 fpm
Vertical suction line risers require approximately 700-1,000 fpm minimum velocity to carry entrained oil droplets upward against gravity back to the compressor.
Which type of joint connection is recommended for permanent refrigerant piping installations in commercial refrigeration systems?
Answer: Brazed connections
Brazed connections provide permanent, leak-resistant joints that withstand pressure cycling, thermal expansion, and vibration typical in refrigeration systems over their service life.
When a long horizontal suction line transitions into a vertical riser, what piping configuration is recommended at the base of the riser?
Answer: Install a P-trap (inverted trap) to accumulate and batch-transport oil up the riser
A P-trap at the base of a vertical suction line riser collects oil so that once a sufficient slug accumulates, refrigerant velocity can carry it upward in a batch rather than a thin film.