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section 8
8 welding
There are many welding technologies and techniques available and used in the metal manufacturing industry. Each has its own features and safety aspects. This section covers general safety issues associated with welding. For hazards related to specific welding techniques, refer to the other resources listed at the end of this section.
Metal Industry Guidelines for Safe Work
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section 8 – welding
8.1 Welding hazards and safe practices hazards • • • • • • • • •
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Burns from welding spatter. Burns from hot materials. Burns from burning clothing. Radiation burns to eyes from welding arc. Radiation burns to skin from welding arc. Electric shock. Eye injury from flying debris. Fire or explosion caused by sparks, heat from conduction, spatter, hot metal. Metal fume fever or respiratory illness from inhaled fumes.
Metal Industry Guidelines for Safe Work
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action points Compressed gas cylinders • • • • • • • •
• •
Follow the supplier’s instructions for use and storage. Do not use unlabelled cylinders. Handle cylinders one at a time. Secure cylinders against falling. Store cylinders upright in a secure area if possible. Set up Hazardous Zones (refer to section 2.6) for compressed flammable gases such as LPG and acetylene. Obtain a Location Test Certificate if this is required (refer to section 2.6). Make sure non-compatible substances such as flammable gas and flammable liquids are separated and stored according to HSNO Act requirements. Store cylinders in a well-ventilated area, and be aware that slow leaks may lead to gas accumulation overnight. When working on a customer’s site, store cylinders upright and away from harm’s way.
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Equipment • • • • •
Keep valves and gauges, hand pieces and hoses clean and free of oil, grease and dirt. Regularly check for leaks (with snoop leak testing solution). Leave cylinder keys in position when welding so gas can be isolated quickly if required. Make sure flash-back arrestors are fitted at all times. Keep equipment (welders, hoses, cords) out of traffic areas so they don’t get damaged or create a hazard for other people.
Metal Industry Guidelines for Safe Work
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section 8 – welding
action points Personal protective equipment •
• • • • • •
Always wear the correct eye protection with a suitable shade of filter lens. Arc welding requires a face shield (helmet). Gas welding and cutting require either glasses, goggles or a face shield. Eye protection for plasma arc cutting will depend on the type of torch used - follow the supplier’s recommendation. Check that auto-darkening lens systems are in good working order. Always wear high-cut gloves that offer forearm protection and are in good condition. Always wear safety shoes/boots. Wear an apron whenever possible. Where fumes are hazardous, respirators or breathing apparatus such as air-fed welding helmets must be used. Make sure your overalls are fire resistant and clean (i.e. not soaked or stained with oils or other flammable liquids).
Practices before, during and after • •
• •
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Always get a hot work permit before proceeding with any welding outside a designated welding workshop (see section 8.3). Check the area you are about to weld for items that may be damaged, or set alight, by the welding flames or hot material. If possible move the part or structure you are working on to a designated hot work area. If flammable hazards or vulnerable equipment, or the welding, can’t be moved away, screen off area and use flameproof covers to isolate the welding operation.
Metal Industry Guidelines for Safe Work
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action points • • • •
Rope off the area and erect a “hot work” sign. Never point a gas torch at anyone, and be aware of where the flame is pointing at all times. Follow the instructions for starting or igniting your equipment. Always mark hot metal as “HOT” with chalk, and rub this off when the piece is cold.
Radiation burns •
Place UV screens around your work area when welding whenever this is practical.
Fire risk •
Make sure you have a fire extinguisher available nearby. Know the location of the hose reels and fire extinguishers near you.
•
Sweep the area you are about to weld or cut into. Don’t weld in very dusty environments – some dust and air mixtures can explode. This is especially true of dusts of flammable materials such as wood, milk powder, coal, plastic
Metal Industry Guidelines for Safe Work
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section 8 – welding
action points •
• • • • • • • •
and textiles. Make sure that there is no exposed flammable material or liquid within the area where sparks or spatter may fall (at least 10 metres). Always check on the other side of the work piece. Paint or something leaning against it may ignite. Use a trained fire watcher (with extinguisher) if necessary. Pick up fallen off-cuts as soon as possible. Cool any heated pieces as soon as you can. Keep checking for fires until surfaces have cooled. Never leave an ignited torch unattended. Don’t let the air become oxygen enriched. Don’t use high-pressure air for cooling or oxygen to power tools. Look also at section 9 of this Guide.
Control of welding and cutting fume •
• •
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Obtain and read the MSDS for all welding consumables and for the metals being welded or cut. Follow the supplier’s recommendations for fume control, and Part 7 of the DOL Health and Safety in Welding booklet. Ensure work areas are well ventilated. If natural ventilation is not sufficient, ensure extraction fans are used and use respirators or breathing apparatus
Metal Industry Guidelines for Safe Work
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action points •
such as air-fed welding helmets. Position yourself so you are up-wind of the fumes.
Electrical
• •
Keep electrical leads clear of water. Do not weld in wet conditions.
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Do not touch live electrical components such as welding electrodes with your bare hands. Keep all insulation on equipment such as cables, torches and guns in good condition. Always turn the supply socket off before pulling the plug out.
Use the correct work (return) clamps and make sure they are connected directly onto the work as close as practical to the weld area.
Metal Industry Guidelines for Safe Work
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section 8 – welding
action points Eyes • • •
!
Always wear safety glasses under welding face shields (helmets). Make sure those helping you are also using the correct eye protection. Protect your eyes when chipping slag off work.
employer’s responsibilities:
Employers need to: • • •
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set up Hazardous Zones (refer to section 2.6) for compressed flammable gases such as LPG and acetylene obtain a Location Test Certificate if this is required (refer to section 2.6) make sure non-compatible substances such as flammable gas and flammable liquids are separated and stored according to HSNO Act requirements.
Metal Industry Guidelines for Safe Work
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more information: Further information: • • • •
Health and Safety in Welding – available from www.dol.govt.nz. Health and Safety in Welding (2004) – Technical Note 7 (TN7) – available from Heavy Engineering Research Association (www.hera.co.nz). Fume Minimisation Guidelines – available from www.wtia.com.au. Welding Health and Safety Assessment Tool – available from www.dol.govt.nz.
8.2 Hot work on tanks and drums hazards •
•
•
Never weld or cut tanks or drums without taking all the safety precautions explained in this section.
Tanks often contain, or have contained, combustible material. If heated, these materials can give off fumes or vapour that can explode! The resulting blast will injure your eyes, ears, lungs or circulatory system and may cause severe burns, broken bones or death. Debris from the tank may inflict cuts on your body.
Metal Industry Guidelines for Safe Work
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action points • •
Proceed only if you know exactly what the container has contained in the past. Look out for:
Volatile-material = flammable on contact with the normal atmosphere. Some examples:
Non volatile-material = releases flammable vapour if heated. Some examples:
Combustible dusts = any solid which burns, and is in the form of a powder, will be explosive in certain dust/air mixes. Some examples:
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Metal Industry Guidelines for Safe Work
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action points •
• •
• •
Clean tanks correctly. – Consult the MSDS for information on the contents of the drum before considering cleaning. – Be aware that mixing water with acids can cause a reaction that may cause the liquid to splatter, which can burn you. – Drain any surplus contents before cleaning. – If contents are soluble, the tank can be washed by filling and emptying it several times. – Non-soluble material (e.g. petrol, grease and oils) must be either boiled with detergent/water or steam cleaned. Check for residues after cleaning (visual and atmospheric tests are recommended. See section 2). If the tank can’t be cleaned it should be filled with water during the welding process.
Don’t start hot work unless you are sure the tank or drum is safe! If in doubt STOP!
Metal Industry Guidelines for Safe Work
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section 8 – welding
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employer’s responsibilities:
Employers need to: • •
make sure your workers and contractors are aware of the dangers of welding or cutting tanks or drums ensure you have clear procedures for cleaning tanks and drums and that these are understood and used by all workers
more information: Further information: •
Hot Work on Tanks and Drums – available from www.dol.govt.nz
8.3 Hot work permits A hot work permit is needed whenever welding is being carried out in a place where it is not normally done i.e. anywhere outside a designated welding workshop. Hot work permits take account of: •
•
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other people working nearby who need to know hot work is happening. They can then avoid working in the same area and remove flammable goods other work that is planned that the welder is not aware of and that may make it unsafe for welding to proceed.
Metal Industry Guidelines for Safe Work
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Information needed from the welder Hot work permits vary, but they generally require the following information from the welder: • • • • • • •
What/when/where the hot work is to be carried out. Names of firewatchers. Location of fire extinguishers. Fire hazards in the location. Whether the alarms are isolated. Any confined space requirements. Visual and atmospheric test results.
Who is authorised to approve a hot work permit? The completed hot work permit form is then taken to the person in charge i.e. project manager or site office. They will look to see if there is conflicting work and will approve/decline or reschedule your work. Once you have approval and the hot work permit is signed by the appropriate person, you may start work.
more information:
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Further information: •
Welding Permit to Work – example available from www.dol.govt.nz.
Metal Industry Guidelines for Safe Work
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section 8 – welding
8.4 Hot work in confined spaces Working in confined spaces is covered in section 3.2 of this Guide – refer to that section before continuing. Tanks, tunnels, vats and closed rooms are all examples of confined spaces. As one of the hazards is that of explosion or fire, it is appropriate that special mention is made of them in this welding section.
hazards • • • •
Tanks may contain flammable vapours. Welding may create or increase vapours present to an explosive level. Toxic fumes will build up or increase as a result of the welding process. Welding and cutting operations cause oxygen depletion so the air becomes hazardous (asphyxiating).
action points •
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Never enter a confined space without an approved entry permit and a safety plan in place.
Metal Industry Guidelines for Safe Work
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action points •
Get the tank atmosphere checked with an atmospheric tester that checks for oxygen content, combustible gases and toxic vapour content. Wear breathing apparatus if necessary. Get adequate ventilation (both supply and exhaust) set up to supply fresh air and extract fumes and “bad” air. NEVER use oxygen or high-pressure air lines for ventilation. NEVER bring gas cylinders into a confined space. During work breaks remove all apparatus from the tank including electrodes and hoses. Make sure the confined space has no liquid whatsoever in it. Make sure all other precautions given in section 3.2 are in place!
• • • • • • •
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employer’s responsibilities:
Employers need to: • • • •
make sure your hot work permit system has a “confined space” section make sure you have a confined space procedure and your workers and contractors are trained to use it ensure you have access to, and use, a trained and certified atmospheric tester make sure test equipment is calibrated and “in date”.
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Metal Industry Guidelines for Safe Work
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