The NSW Resources Regulator recently issued a safety bulletin following repeated incidents involving the failure of safety critical systems on mobile plant.
These incidents have resulted in vehicle rollovers and collisions, and all incidents occurred with road-registered plant operating on active haul roads within mining operations.
Although nobody was injured in any of these incidents, the bulletin said several incidents had the potential to result in fatalities.
The incidents referred to below have one or more common factors:
In one incident, a road-registered medium, rigid truck was fitted with a watercart and was operating in an open cut coal mine, and the truck was descending a ramp while operating in drive with service brakes being used to control the speed.
Since the transmission was in drive, the exhaust brake was ineffective, and as the speed increased, the operator tried unsuccessfully to slow the truck.
The operator then steered into a windrow to slow the truck, which resulted in the truck rolling and the operator suffered a fractured wrist and bruising.
An independent investigation identified the cause of the incident as driver reliance on service brakes and brakes out of adjustment.
The vehicle should have been driven in a lower gear and the exhaust brake should have been used to control the speed of the vehicle.
The inspection identified five of the six brake units fitted were out of adjustment even though they had been adjusted during a service two weeks prior.
In another incident, a mobile slew crane rolled following a loss of brakes.
The crane had arrived and was being escorted to the jobsite, and while descending the third consecutive ramp to the work area, the brakes failed to slow the vehicle.
The exhaust brake was not effective because the crane was being driven in a high gear.
While trying to slow the crane, the operator steered the crane into a windrow at the side of the road causing the crane to roll. No injuries were reported.
An independent investigation identified the cause of the incident as incorrect use of the brakes and brakes out of adjustment.
The operator relied on the service brake and failed to adequately use the exhaust brake to control the descent speed of the crane, while seven of the eight brake units were also found to be adjusted outside roadworthy limits.
In a third incident, a fitter was driving a light vehicle through the pit at the end of nightshift, and the driver hit a small bump in the road and lost all steering.
The vehicle travelled 30 metres and ran up a windrow which turned the vehicle onto its side, however, the rollover did not result in any injuries either to the driver or the passenger.
The light vehicle’s steering arm failed, causing the vehicle to veer onto the wrong side of a haul road, which was not active at the time but was scheduled to be active later that night.
The loss of steering was cause by failure of the ball joint in the steering tie rod assembly.
The safety bulletin subsequently made a number of recommendations:
1. Safety critical systems such as braking and steering systems on mobile plant must be inspected, tested and maintained so that the systems operate effectively and remain effective.
2. Road-registered vehicles such as light vehicles and trucks used in mines may be subjected to higher loads or environmental factors which adversely affect service life. Maintenance strategies must consider OEM recommendations for:
3. The competency of tradespersons working on safety critical systems should be assessed and verified to ensure work is carried out correctly and does not pose a risk to the operation of the vehicle.
4. Following work on safety critical systems, the system should be inspected and tested to verify that it is safe to operate, before re-entering service.
5. Mines must have systems in place to confirm that safety critical systems, such as brakes and steering on hired or contractor supplied items of plant, are fit for use and have been adequately maintained.
6. Mines should review their introduction to site processes to ensure they include suitable and adequate verification of brakes. Mines should also ensure steering systems are maintained, tested, inspected, adjusted and have a suitable remaining service life.
7. Where mines do not directly perform maintenance on hired or contractor-provided mobile plant, mines should review hire or contractor management plans to include verification of service providers to maintain safety critical systems effectively. This should include triggers for short- term hirers that develop into extended hire periods and contractors who enter sites periodically over months or years.