Welding, brazing and cutting are essential processes in manufacturing industry. All these processes depend crucially on industrial gases.
BCGA is committed to ensuring SAFE use of industrial gases in these processes and produces several useful guidance documents, as detailed below, which operatives and their employers should be familiar with.
A key hazard generated within these processes is FUME - and precautions should be taken to avoid its inhalation, not only by operatives doing the welding/brazing/cutting, but also by others nearby.
BCGA has engaged with the HSE and others via the Welding Fume Team to try to influence attitudes and behaviours with respect to FUME, particularly in encouraging the use of appropriate Personal Protective Equipment.
BCGA has published a Safety Alert on the hazards of FUME, TIS 24. The Welding Fume Team has produced a website www.badairday.info which explains in detail the safety concerns associated with FUME and which encourages appropriate safe behaviour.
Fuel gases are mostly hydrocarbon based and each has its own unique properties. The choice of a fuel gas is based on its ability to burn in air or oxygen and will be dependent on the specific requirements of the job, as well as the location at which it is being used. There are several useful fuel gases of which acetylene and propane are the most common. Following a major review of legislation in 2014, acetylene was placed under The Acetylene Safety (England and Wales and Scotland) Regulations 2014. These regulations require that all mobile systems shall be fitted with a purpose designed regulator for acetylene, a flashback arrestor incorporating a non-return valve and a pressure and/or temperature sensitive cut-off valve.
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 7 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 Code of Practice 4 and, for acetylene, Code of Practice 6.
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 Code of Practice 7, Code of Practice 4 or Code of Practice 6 are the appropriate BCGA publications 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 from a single cylinder, local to the welding equipment, then BCGA Guidance Note 7 gives detailed recommendations. Fixed supply systems are, as before, defined in Code of Practice 4.
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 Welding Committee WEE/18.
To help maintain gas equipment in good order BCGA also publish Technical Information Sheet 18 to help identify the inspection and replacement date markings on certain items, and publish Technical Information Sheet 19 to provide advice on refurbishing handheld blowpipes and regulators.
Within BCGA, TSC3 is the Technical Sub-Committee that covers this topic. BCGA members interested in this subject should consult the minutes of TSC3 within the Meetings section of the Members area.
The following documents are available from the Publications section:
- CP4, Industrial Gas Cylinder Manifolds and Gas Distribution Pipework (excluding acetylene).
- CP5, The design and construction of manifolds using acetylene gas from 1.5 bar to a maximum working pressure of 17 bar.
- CP6, The Safe Distribution of Acetylene in the Pressure Range 0-1.5 bar (0-22 lbf/in²).
- CP7, The Safe Use of Oxy-Fuel Gas Equipment (Individual Portable or Mobile Cylinder Supply).
- GN7, The Safe Use of Individual Portable or mobile Cylinder Gas Supply Equipment..
- TIS 15, Model Risk Assessment for the Storage and use of oxyacetylene cylinders.
- TIS 18, Gas equipment inspection / replacement date marking.
- TIS 19, Refurbishment of handheld blowpipes and regulators used with compressed gases for welding, cutting and related processes.
- TIS 24, Welding Fumes - Safety Alert.
- TIS 32, Acetylene or propane (for welding, cutting and allied processes).