Exploding jumbo tyre injures trade assistant

A trade assistant has suffered injury after a jumbo tyre was over-inflated and exploded at a large underground metalliferous mine in New Zealand.

WorkSafe NZ issued a safety alert which said the explosion incident happened as an electronic gauge used to measure the inflation pressure was wrongly set on bar and not psi. Front jumbo tyres are required to be pressurised to 140 psi and compressed air on-site was only capable of supplying approximately 90 psi. The safety alert said that it is common practice in the mining industry to inflate jumbo tyres to a working pressure of 140 psi using pressurised nitrogen. This is inherently dangerous if there is no engineered pressure release control in the inflation process. In addition, the tyre cage was not certified for safe use by an engineer.

According to WorkSafe NZ, 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 inflation methods other than compressed nitrogen.

It also advises that gauges used 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.

Meanwhile, 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, and the use of solid-filled tyres should be considered to eliminate the risk.

WorkSafe NZ states that principal hazard management plans and principal control plans should be reviewed regularly to ensure the hazards are fully controlled.

The injured trade assistant has returned to work since the incident.

Image credit: ©iStockphoto.com/Alan Lagadu