The WA Department of Mines, Industry Regulation and Safety has made a number of recommendations to combat the risks associated with lightning strikes.
Electrical storms occur year-round in Western Australia. They are typically episodic and highly variable in nature, with lightning strikes posing a hazard for mine workers.
These incidents have highlighted several contributory factors and resulted in a number of recommendations for workers on WA mines, which the Department of Mines, Industry Regulation and safety sets out in its Mines Safety Bulletin.
WA mining operators have experienced several incidents of vehicles being struck by lightning over the past three years.
A lightning strike on a vehicle may cause pyrolysis within the tyre, where heating of the rubber (inner liner) releases gaseous, volatile organic compounds into the tyre’s air chamber.
Under certain temperature, pressure and concentration conditions, this volatile combination of air and fuel can become an explosive mixture and ignite.
Pyrolysis may result in tyres exploding unexpectedly, with this type of catastrophic failure possibly occurring after a delay of several hours, placing workers at a significant risk of serious or fatal injury.
In some instances, tyre pyrolysis has occurred immediately after the event, and can lift the vehicle or cause debris to be propelled into the vehicle or over hundreds of metres.
While it is safer to take shelter in a vehicle during an electrical storm, many mine vehicles including haul trucks and other heavy vehicles are not designed to protect operators from the potential effects of a lightning strike or to be a Faraday cage.
Vehicles in exposed locations may even serve to attract lightning.
A lightning strike on a moving vehicle may introduce other hazards to workers, including:
- short-circuiting batteries, tyres and flammable material, resulting in burns
- arc strike causing temporary blindness, resulting in a loss of vehicle control
- failure of electric assisted braking and steering, resulting in a loss of vehicle control.
Some important contributory factors are also present when lightning strikes, including:
- hazards associated with lightning are not always identified
- vehicles used in mining operations that are not designed to protect operators from the potential effects of a lightning strike
- that the effects of pyrolysis events may result in tyres exploding unexpectedly, either immediately or after a delay of several hours.
In order to combat the risks associated with lightning strikes, the WA Department of Mines, Industry Regulation and Safety recommends the following actions are undertaken by mine operators:
- A review of the risk assessment for mine workers being in the open or operating vehicles during an electrical storm where there is a possibility of lightning strikes
- A control of the hazards and risks related to electrical storms and lightning strikes to adequately reduce mine workers’ exposure to potential harm
- A review of procedures related to working in the open or operating vehicles when there potential for exposure to lightning
- A requirement to provide mine workers with sufficient warning of a potential lightning event and allow time to take shelter in a building with lightning protection