313A Piping, Brazing & Leak Detection

Question 1

When brazing copper-to-copper refrigerant joints, which brazing alloy is most commonly specified?

Accepted Answer

BCuP-5 (15% silver, copper-phosphorus)

Answer

Soft solder (50/50 tin-lead)

Answer

BCuP-2 (copper-phosphorus, no silver)

Answer

BAg-7 (56% silver)

Question 2

Why must dry nitrogen be purged through copper tubing during the brazing process?

Accepted Answer

To prevent cupric oxide scale from forming inside the pipe

Answer

To cool the tubing faster after brazing

Answer

To increase the flow rate of the brazing alloy

Answer

To pressure-test the joint immediately after brazing

Question 3

What is the minimum recommended overlap length for a brazed socket joint in refrigerant copper tubing?

Accepted Answer

Equal to the tube outside diameter

Answer

Equal to the tube wall thickness

Answer

Half the tube outside diameter

Answer

Three times the tube wall thickness

Question 4

When cutting copper refrigerant tubing, which tool provides the cleanest cut with the least internal deformation?

Accepted Answer

Wheel-type tubing cutter

Answer

Hacksaw

Answer

Reciprocating saw with metal blade

Answer

Angle grinder with a cutoff disc

Question 5

What is the primary hazard when brazing refrigerant lines that have not been fully purged of refrigerant vapour?

Accepted Answer

Phosgene gas can form from refrigerant decomposition in the flame

Answer

The brazing alloy will not bond to the copper

Answer

The torch tip will overheat and require replacement

Answer

Excessive oxidation will blacken the outside of the tubing

Question 6

Which flux is required when brazing copper tubing to a brass or steel fitting?

Accepted Answer

A proper brazing flux (AWS Type FB3-A or equivalent) must be applied

Answer

No flux is needed on any copper joint

Answer

Standard paste solder flux is sufficient

Answer

Flux is only required when using oxygen-acetylene equipment

Question 7

What nitrogen flow rate is typically recommended when purging copper refrigerant piping during brazing?

Accepted Answer

A low positive flow just sufficient to displace oxygen (1–5 CFH)

Answer

As high as possible to ensure complete purging (above 50 CFH)

Answer

Nitrogen pressure must match the system working pressure

Answer

No specific flow rate — opening the valve briefly is adequate