CRST Piping, Tubing & Brazing Techniques 3

Question 1

At approximately what temperature range does silver-phosphorus-copper (BCuP-5) brazing alloy flow and fill refrigeration copper joints?

Accepted Answer

1,200–1,500°F (649–816°C)

Answer

300–400°F (149–204°C)

Answer

700–800°F (371–427°C)

Answer

1,800–2,000°F (982–1,093°C)

Question 2

After completing a brazed joint in a refrigeration line, what is the correct method for allowing the joint to cool?

Accepted Answer

Allow the joint to air cool naturally without applying water or forced cooling

Answer

Quench immediately with cold water to lock in the joint structure

Answer

Apply ice directly to the joint to prevent overheating adjacent components

Answer

Use compressed air to blast cool the joint rapidly

Question 3

When brazing copper tubing to a brass fitting (such as a service valve body), what additional step is required that is NOT needed for copper-to-copper joints?

Accepted Answer

Apply brazing flux to the joint before heating, because BCuP alloys are not self-fluxing on brass

Answer

Use a higher flow-rate nitrogen purge

Answer

Pre-tin the brass fitting with soft solder first

Answer

Use a different torch tip to achieve higher heat concentration

Question 4

What is the correct tool and technique for cutting ACR copper tubing to achieve a clean, square, burr-minimized cut?

Accepted Answer

Tubing cutter rotated around the circumference with gradually increasing blade pressure

Answer

Hacksaw with a coarse blade drawn across the tubing

Answer

Reciprocating saw with a metal-cutting blade

Answer

Aviation snips or pipe shears for quick cuts

Question 5

Immediately after cutting copper ACR tubing with a wheel-type tubing cutter, what mandatory step must be performed before brazing?

Accepted Answer

Ream the inside of the cut end to remove the inward burr created by the cutting wheel

Answer

Apply a thin coat of refrigerant oil inside the tube end to ease fitting insertion

Answer

Heat the cut end briefly to anneal and soften the copper

Answer

Sand the outside of the cut end with fine emery cloth only

Question 6

How should ACR copper tubing be stored and handled on a job site to maintain its factory cleanliness?

Accepted Answer

Keep both ends capped or plugged with factory or field caps until the moment of installation

Answer

Leave both tube ends open so pressure equalizes with atmosphere

Answer

Store vertically only, with one end resting in a bucket of water

Answer

Wrap the entire length in wet cloth to maintain metal flexibility

Question 7

In a refrigeration system with multiple evaporators at different elevations, what is the function of individual suction line traps installed at each evaporator outlet before a common riser?

Accepted Answer

To prevent liquid refrigerant from draining back into an idle evaporator during off-cycles

Answer

To equalize suction pressure between all evaporators

Answer

To measure refrigerant flow from each evaporator independently

Answer

To act as oil separators before the refrigerant reaches the compressor