The Queensland Department of Natural Resources Mines and Energy has issued a mine safety alert after an articulated water cart overturned and pinned the operator in the cab. The operator was hospitalised for assessment and treatment of fractures and bruising.
According to the safety alert, in September 2018, an operator loaded an articulated water cart (Cat 740B) and was moving up a ramp on a mine’s tailings dam. The engine then stalled for unknown reasons, and the vehicle ran away backwards down the face of the tailings dam wall. The vehicle overturned at the bottom, pinning the operator in the cab.
The Department of Natural Resources Mines and Energy said the pump supplying hydraulic pressure to the brake system stopped when the engine stalled.
Despite this, a further two braking options should still have been available to control the water cart:
- the secondary service brake system, normally supplied by brake accumulator pressure in an emergency situation
- the park brake system.
In this instance, the service brake accumulator pressure was too low to provide effective braking. It is thought the operator did not have enough time to activate the park brake switch on the dashboard before losing control of the water cart.
According to the QLD Department of Natural Resources Mines and Energy-
- Machines using accumulators to maintain service braking under hydraulic pump failure or engine stalling, should have accumulator dry nitrogen pre-charge pressures checked by trained personnel every 250 hours.
- Service brake accumulator functionality should be checked daily as part of the machine prestart regime.
- Consult with the Original Equipment Manufacturer (OEM) for specific procedures on brake accumulator pre-charge and functionality testing.
- Steering system accumulators should be inspected and tested in accordance with OEM procedures and recommendations.