Welding, brazing and cutting are essential processes in manufacturing industry. All these processes depend crucially on industrial gases.

Brazing requires that the work be heated to the correct temperature for the process to take place. There are several different methods for achieving this heating, but the use of an oxygen/fuel gas burner is the most common. Typically oxygen/propane or oxygen/acetylene are used, with the higher temperature of the oxygen/acetylene flame giving maximum flexibility. BCGA Code of Practice CP7 defines how to design, operate and maintain portable and mobile systems for oxygen/fuel gas processes. Fixed installations, with cylinder manifolds supplying gas via distribution piping systems, are specified in BCGA Codes of Practice CP4 and CP6 (see below).

Cutting of metals is commonly carried out using oxygen/fuel gas equipment. The process consists of heating the work using the flame, and then using excess oxygen to burn the metal. Depending on the scale of the job either oxygen/ propane or oxygen/acetylene systems can be used. As for brazing CP7 or CP4 or CP6 are the appropriate BCGA Codes to refer to.

Welding can be either gas welding or electric arc welding. For gas welding of ferrous metals the flame temperature must be the highest possible to get the metal to melting point. Thus only oxygen/acetylene is suitable for this process. Modern electric arc welding requires the use of shielding gas to protect the weld from the atmosphere.

Sometimes this shielding gas is a single gas, very often argon, but the use of gas mixtures is increasingly common, with mixtures tailor-made according to the metal being welded. Where the shielding gas is provided by a single cylinder local to the welding equipment then BCGA Guidance Note GN7 gives detailed recommendations. Fixed supply systems are as before defined in CP4. This area of gas use is well supported by published standards, most of which are either European (EN) or international (ISO). BCGA is very active within BSi in the development of these standards, via the committee WEE18.

TSC3 is the relevant Technical Sub-committee for this topic. Those interested in the use of gas for these processes should consult the minutes of TSC3 for up-to-date information.

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