The Caterpillar 777F rear dump truck was travelling down a ROM ramp when it lost engine power resulting in the truck wheels locking on and the truck sliding for approximately 60 metres, coming to a halt on the haul road.

The emergency steering allowed the operator to retain control of the truck and no injuries to personnel were incurred.

A non-genuine relay, installed for the Automatic Fire Suppression System, had been dislodged and worked loose from its position due to vibration.

The relay was installed to control power supply between the fire suppression system control module, engine electronic control module and the “E Stop” switches.

When the relay dislodged it open circuited the power supply to the engine electronic control module, causing the truck engine to suddenly shutdown without warning.

The site's six-monthly inspection regime for automatic fire suppression systems did not include an inspection of this particular relay, according to the department.

The fire suppression system did not discharge during the incident.

“All vehicles fitted with fire suppression systems should comply with the requirements of the relevant Australian Standards, in particular AS 5062-2006 Fire protection for mobile and transportable equipment,” the department said.