Handbook-Brazing & Soldering

12 Other Soldering Applications It is beyond the scope of this book to describe all the different uses of the air-acetylene and air-propane flames for soldering. In air-conditioning and refrigeration service work, the soldering torch (which may also be used for brazing small-diameter tubing connections) is invaluable. Further, special stems are available, which attach directly to soldering torch handles, for detecting leaks of the ”halide” refrigerant gases (marketed under the brand names ”Freon”, ”Ucon”, etc.). These leak detectors all take advantage of the fact that the halide gases (chlorine, fluorine, bromine) give distinctive colors to a flame when brought in contact with hot copper. Further, the color changes as the concentration of the halide changes, so that it is easy to pinpoint the source of the leak. Open-flame soldering is also widely used for finishing off joints in copper wiring systems to make certain that they will remain fully conductive. The thing to remember about this type of joint is this: that copper wire is normally hard- drawn for maximum tensile strength, and that the heat required to make up a soldered connection will anneal the copper and greatly reduce that strength. However, there are several ways to make up twisted joints so that loss of strength can be avoided.