Welding, cutting and allied processes
Welding, brazing and cutting are essential processes in the 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 documents, as detailed below, which Employers and their operatives should be familiar with. At each workplace where welding cutting and other allied process are in-use a suitable and sufficient risk assessment shall be carried out and, as necessary, appropriate controls put in place. BCGA TIS 15 provides information on the potential hazards (associated with gases) and possible controls.
When used correctly, gases are safe. Gases have hazards and their storage, handling and use should be included in your risk management process for controlling health and safety risks in the workplace. Each gas has its own hazardous properties, which may include being flammable, being asphyxiant and, for oxygen, the hazards from enrichment. BCGA GN 11 identifies potential hazards from the escape, leak or accumulation of gases into the workplace and the associated risks.
There are additional hazards associated with welding and hot cutting processes, including from the fluxes and materials used. The hazards include excessive heat, exposure to bright direct and reflected light, including ultraviolet light, and the inhalation of welding fume, such as airborne gases and very fine particles. All activities should only be carried out by competent people and must be subject to risk assessment with suitable controls. Controls such as:
- Local exhaust ventilation (LEV), including regular maintenance and the use of visual indicators;
- Health surveillance, including biological monitoring and personal air sampling;
- Personal protective equipment, including respiratory protective equipment.
BCGA has engaged with the Health Safety Executive (HSE) and others via the Welding Fume Health Partnership to try to influence attitudes and behaviours with respect to welding fume, particularly in encouraging the use of appropriate controls and the safety of those involved.
The HSE provide guidance for the Control of Substances Hazardous to Health (COSHH) for welding and specific guidance on managing welding fume. BCGA supports the Chartered Society for Worker Health Protection (BOHS) and its 'Breathe Freely' campaign to control exposure to hazardous substances, such as welding fume, and to prevent occupational lung disease in the construction industry. Lots more information is available on their website - www.breathefreely.org.uk.
BCGA SA 03 highlights the hazards from welding fume.
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. For information on these refer to BCGA TIS 32. Following a major review of legislation in 2014, acetylene was placed under The Acetylene Safety (England and Wales and Scotland) Regulations. 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, either oxygen / acetylene or oxygen / propane are used, with the higher temperature of the oxygen / acetylene flame giving maximum flexibility. BCGA CP 7 defines how to design, operate and maintain portable and mobile systems for oxygen / fuel gas processes. Fixed installations, which supply gas through a control and distribution system, are specified in BCGA CP 4 and, for acetylene, BCGA CP 6.
Cutting of metals is often 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 / acetylene or oxygen / propane systems can be used. As appropriate refer to BCGA CP 4, BCGA CP 6 and BCGA CP 7.
There are several options when welding, including gas, electric arc, metal inert gas (MIG), tungsten inert gas (TIG), etc. 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.
Welding, cutting and allied processes are well supported by published standards, which are increasingly either European (EN) or International (ISO). BCGA is very active within BSI in the development of these standards, via the Welding Committee WEE/18.
All gas equipment must be suitable for the purpose for which it is provided, be safe to operate, and be subject to regular inspection and maintenance. BCGA CP 7 sets out the requirement for carrying out assembly checks, before and after use checks, and a periodic thorough inspection. Guidance on carrying out a thorough inspection is provided in BCGA GN 44 and BCGA TIS 18 provides information to assist in identifying the inspection and replacement date markings on certain items.
Within BCGA, welding, cutting and allied processes are the responsibility of Technical Sub-Committee (TSC) 3. Members can access information on TSC3 via the ‘Members' area
The following documents are available from the Publications section:
- BCGA CP 4 - Gas supply and distribution systems (excluding acetylene).
- BCGA CP 5 - The design and construction of manifolds using acetylene gas from 1.5 bar to 25 bar.
- BCGA CP 6 - The safe distribution of acetylene in the pressure range 0 - 1.5 bar.
- BCGA CP 7 - The safe use of oxy-fuel gas equipment (individual portable or mobile cylinder supply).
- BCGA GN 11 - The management of risk when using gases in enclosed spaces.
- BCGA GN 44 - Portable or mobile cylinder gas equipment. Thorough inspection.
- BCGA TIS 15 - Model risk assessment for the storage and use of gas cylinders for oxy - fuel applications.
- BCGA TIS 18 - Date marking of gas accessories.
- BCGA TIS 29 - Oxy-fuel gas equipment. Selection and assembly
- BCGA TIS 32 - Acetylene or propane (for welding, cutting and allied processes).
- BCGA SA 1 - Safety Alert 1 - The hazards of using incompatible regulators with acetylene
- BCGA SA 2 - Safety Alert 2 - Hydrogen and oxygen flames generated from electrolysis of water - Safety devices
- BCGA SA 3 - Welding fumes