Handbook-Brazing & Soldering

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Brazing Copper Tube To Fittings For many years, the water piping systems installed in new residences and other buildings have usually been fabricated from copper tubing and socket- type fittings. The materials for such a system may be more costly than steel pipe with threaded fittings, but cost of installation is less, thanks to the flexibility of the tubing and the speed and ease with which joints can be made up. In addition, the system has no rust problems, and is likely to prove trouble-free for the life of the buildings. For similar reasons, most radiant-heating systems also use copper tubing. Hospital oxygen piping systems are invariably made up with copper tubing. Copper tubing systems are also used in industrial plants for water and other fluids, even for steam in some cases. While most copper piping systems use relatively small-diameter tubing, in the 1 cm to 5 cm range (3/8 in. or 2 in.), some industrial systems use tube as large as 20 cm (8 in.) or larger. The fittings manufactured for use with copper tubing may be either wrought copper or cast brass. In either case, the depth of the fitting socket into which the tube is inserted is normally sufficient so that full-strength joints – by which we mean joints as strong as the tubing itself when subjected to short-duration tensile forces – can be made up with either soldering alloys (”soft solders”) or brazing alloys. Because soldering is both quicker and easier than brazing, and because the cost of soft solder is less than the cost of a brazing alloy in most cases, more copper tubing systems are soldered than brazed. The temperature levels required for soldering are so low that the oxy-acetylene welding torch is seldom used to make up soldered joints. For brazed joints, however, the oxy-acetylene flame has definite advantages over lower-temperature gas flames, such as those produced by air-acetylene and air-propane torches.