Silver brazing

Silver brazing: Brazed joints are very strong and considered to be the best method of making leakproof connections. The correct procedure is as follows:

CAUTION: Before any brazing is begun, all of the refrigerant must be evacuated from the system as instructed in the section on repairing leaks in the sealed system.

1. Clean and burnish the joints with fine sandpaper. The parts to be brazed must be fitted snugly and accurately, clean, and securely supported so that no part can move during brazing.
2. Apply the recommended flux (fig. 19) for the alloy being used to the outside of the joint after the tubes are fitted snugly together. Be sure the joint is firmly supported to avoid movement during brazing or cooling.
3. Heat the joint evenly with a torch (figs. 20 and 21) using a figure-8 motion. More heat will be needed for larger tubing. Acetylene/oxygen tanks (along with the appropriate lines and tips) can create more heat. The kit is available at refrigeration supply houses. Start heating about one-half inch to one inch away from the joint. Never hold the torch in one spot. Keep it moving until the joint turns cherry red. This color indicates that the joint has reached the temperature at which silver alloy flows, 1,145°F.
4. Apply the brazing alloy at the top and allow it to seep into the heated joint. Since alloy always flows toward heat, hold the torch at the back of the joint to let the alloy flow into the joint and fill it up.
5. Cool the joint with a piece of wet rag, then use hot water and a brush to clean it. This is important because any remaining flux will tend to corrode the tubing and block a leak that might show up.

CAUTION: Always buy alloy that does not contain cadmium (Cd) as cadmium fumes are highly poisonous! If the brazing alloy contains any amount of cadmium, do not inhale the fumes or allow them to come in contact with your eyes or skin.

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