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Electrical hazards

HSE issues safety alert on welding fume

New evidence shows exposure to mild steel welding fume can cause cancer. Employers should use suitable controls for all welding work. The current guidance on mild steel welding is out of date and will be updated as soon as possible to take account of this new evidence.

Safety alert

The arc welding process requires a live electrical circuit. This means that all arc welders using hand held equipment will be at risk of electric shock and electrical burns. The risk for MIG/ MAG and TIG welding is much less as the welding current is normally switched on and off using the trigger or foot switch.

For all arc welding processes the essentials of safe practice are:

The welder is responsible for daily checks of equipment and reporting defects. Management should implement a programme of regular checks for fixed and mobile welding sets. Further guidance on maintaining electrical equipment is available on the Maintaining Electrical Safety web page and in HSE publication HSG107 – Maintaining portable and transportable electrical equipment.

Stray welding currents

Stray welding currents are electrical currents that return to the welding set by paths other than along the welding return cable. Stray currents may be substantial and comparable to the welding current resulting in a risk of electric shock, burns and damage to property. Stray currents are more likely if the welding return path exhibits a high electrical resistance eg the return is clamped onto a rusty surface rather than clean metal.

When welding on large structures and pipework installations clamping the welding return to handrails, pipes or the frame of the structure should be avoided unless they form part of the work piece itself.

Some older MMA welding sets are built specifically to use an earth return cable that is shared between several welding sets. This type of equipment was common in the shipbuilding and ship repair industry. This type of welding set up should only use equipment that is designed to be used this way. The current return path should be as short as possible and may need to be carefully planned to ensure risk is minimised.

3 phase electrical supplies

When using three-phase welding circuits or single-phase circuits derived from different phases of the mains supply, the welding positions connected to different phases or transformers should be segregated by partitions, or distance, whenever it is reasonably practicable to do so. This reduces the possibility of electric shock from simultaneous contact with any parts of two different systems, irrespective of the voltage of either one to earth.

Welding in environments where there is an increased risk of electric shock

If you are in control of operations where there is a need to:

You may need to provide an insulating mat or some other dry platform, so welders are not in direct contact with wet or conductive surfaces. Often a wooden pallet or rubber floor mat will suffice. The mat should be large enough to offer protection to the welder if they are required to kneel or lie down to complete the task.

Normal welding PPE is not designed to prevent electric shock however it does provide some protection. The electrical resistance of clothing that is damp or contaminated may be significantly reduced giving rise to a greater risk of electric shock.

When MMA welding it is better to use a welding set that has an open circuit voltage (no load voltage) limiting device. These devices reduce the risk of electric shock from inadvertent contact with the electrode.

For further information see the Electrical safety web pages, in particular the page for work with electrically powered equipment.

Updated 2019-03-20