A worker received an electric shock while changing a welding rod as part of electric arc welding. The initial shock caused the person to fall. He then received a second shock when the electrode contacted his chest. The injured person required resuscitation and hospitalisation for treatment.
The work was being undertaken in a confined space where conditions were hot and humid. The injured person’s clothing was damp with sweat.
The welding power source was capable of a maximum open circuit voltage of 79V AC rms. A hazard or voltage reducing device was not used.
Electrical current will pass through the body when contact is made with the electrode or an exposed part of the welding circuit, which can result in electric shock or electrocution.
Workers are exposed to the maximum open circuit voltage when the power source is energised, and an arc is not drawn (the voltage reduces when the welding arc is drawn).
The risks associated with electric shock from arc welding are relative to the maximum open circuit voltage being used and the work environment. Higher voltages and hazardous working environments expose workers to greater risks.
You must limit the maximum open circuit voltage in consideration of where the welding will be done. Welding in areas of increased risk of electric shock e.g. confined spaces, should be limited to a maximum open circuit voltage of 48V AC rms. The open circuit voltage should be further limited to 25V AC rms where the working environment is hot, humid or damp to account for decreased skin resistance. Australian Standard 1674.2 categorises working environments and sets the maximum permitted open circuit voltage for each category.
A voltage reducing device (VRD) will limit the maximum open circuit voltage to a predetermined level.
An RCD will not protect a person from electric shock from a welding electrode. However, the RCD is important to protect against faults on or from the primary side of the power supply, i.e. the power lead, primary winding and frame, or between the primary and secondary power sources.
Welding personal protective equipment (PPE) is not designed to prevent electric shock, but it does provide some protection. The electrical resistance of damp or contaminated clothing may be significantly reduced, giving rise to a greater risk of electric shock.
You must identify all hazards including electrical and fire hazards and assess the associated risks. You must implement effective controls specific for the task and work environment, including:
- equipment used should be suitable for the work environment and activity. For example, in a confined space and potentially damp situation a VRD should be used to limit the maximum open circuit voltage to 25V AC rms in accordance with AS 1674.2.
- equipment is inspected, tested and maintained routinely by a competent person. Use a qualified electrician to do any electrical repairs and perform electrical maintenance and testing. Never used damaged or faulty equipment.
- machine terminals and lead connections are clean and tight - only use welding leads that are fully insulated throughout their entire length with insulated fasteners.
- protect both the electrode lead and the work lead from damage
- avoid direct contact with the work piece or with any metal in contact with the work piece
- do not make direct contact with the electrode including when changing electrodes
- use insulated electrode holders and accessories
- always wear dry welding gloves when handling equipment that is energised.
- never attempt to connect or change welding leads before first isolating the power source
- do not stand on damp ground or in water when welding or perform arc welding when wet or damp
- work on a well-insulated floor wherever possible and wear rubber insulated shoes.
Control all confined space risks when welding; including provision of ventilation, provision of a safety observer who can immediately isolate the power and give assistance in an emergency, and the preparation and practice of emergency response plans including rescue of a person from the confined space.
- SafeWork NSW Code of Practice: Welding Processes
- SafeWork NSW Code of Practice: Confined Spaces
- SafeWork NSW Code of Practice: Managing electrical risks in the workplace
- AS 1674.2-2007 r.2018 Safety in Welding and Allied Processes, Part 2 Electrical
- AS 60974.1-2020 Arc Welding Equipment - Welding power sources
- Contact Safework NSW on 13 10 50 or visit www.safework.nsw.gov.au