WorkSafe New Zealand issued a safety alert following an incident in which a trade assistant at a large underground metalliferous mine was injured when a Jumbo tyre was over-inflated to the point it exploded.
According to New Zealand’s safety regulator, the over-inflation happened after an electronic gauge used to measure the inflation pressure was wrongly set on Bar and not psi. The worker is now back at work, but the injuries could have been fatal.
“Front Jumbo tyres are required to be pressurized to 140psi. Compressed air on site was only capable of supplying approximately 90 psi,” WorkSafe says in its safety alert.
“It is common practice in the mining industry to inflate Jumbo tyres to a working pressure of 140 psi, using pressurized nitrogen. This is inherently dangerous if there is no engineered pressure release control in the inflation process.”
WorkSafe says the tyre cage was not certified for safe use by an engineer.
“Because front tyres on development Jumbos require inflation pressures higher than can be achieved using an existing compressed air source, consideration should be given to using an existing compressed air source, consideration should be given to using inflation methods other than compressed nitrogen,” the safety alert states.
“Gauges for inflating tyres must be accurate and have an appropriate operating pressure range so inflation pressure can be read accurately, and not be interchangeable with other systems.
“Installation of an “air compressor booster” should also be used where pressures need to be increased above normal compressed air being supplied. The maximum system pressure can be set at levels well below that of compressed nitrogen cylinders.
“The use of solid-filled tyres should be considered to eliminate the risk.
“Principal Hazard Management Plans and Principal Control Plans should be reviewed regularly to ensure the hazards are fully controlled.”
More information about this safety alert is available on WorkSafe New Zealand’s website.