An analysis of 81 underground fires involving diesel powered, mobile equipment in NSW mines between July 1990 and September 2000 has indicated that virtually all of the fires could have been prevented by better maintenance.

The most common cause was diesel or hydraulic oil spraying, onto hot components when pipes and hoses wore through or burst. Oil does not ignite on its own but needs to be sprayed onto a hot exhaust manifold, a hot turbocharger or onto a worn out and arcing electrical wire.

If the engine is turned off, the hydraulic fluid or diesel oil flow generally stops and the fire goes out but in many cases oil soaked dirt and dust or deposits of grease on the equipment provides enough fuel to keep the fire burning.

That's where cleanliness and maintenance comes in. Regular cleaning will remove the secondary fire fuel and make it easier to find and fix the problems that can cause fires.

The other common cause of fires was electrical, again a maintenance issue, with batteries breaking loose or cables breaking and shorting out onto components or vehicle frames to provide the spark needed for ignition.

Some fires were also related to brake retarder systems but this turned out to be more of a training issue associated with the introduction of new equipment at one site.

The figures on underground equipment fires are from a scoping study initiated by the mining industry and the department during a meeting in Cobar in 1996. A report was presented in 1998 and it was decided to incorporate the information into the guidelines for safer mining. Draft guidelines were presented to the Metalliferous Safety Advisory Committee at Broken Hill in 1998 and the guidelines were completed in February 1999.

The underground equipment fires that have occurred since 1990 have not resulted in serious injury but fires are unnecessary underground dangers that must be eliminated.

For further information on how to prevent fires on underground equipment, contact Bob Johnson, Inspector of Mechanical Engineering on 08 8080 0622 or email

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