SafeWork NSW recently issued a safety alert following an incident in which 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, and he then received a second shock when the electrode contacted his chest.
The injured worker 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, and a hazard or voltage reducing device was not used.
“You must limit the maximum open circuit voltage in consideration of where the welding will be done,” the alert said.
“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.”
Furthermore, 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.
Furthermore, a voltage reducing device (VRD) will limit the maximum open circuit voltage to a predetermined level.
While an RCD will not protect a person from electric shock from a welding electrode, the RCD is important to protect against faults on or from the primary side of the power supply.
The alert said PCBUs must identify all hazards including electrical and fire hazards and assess the associated risks, and implement effective controls specific for the task and work environment, including:
“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,” the alert said.