According to the regulator, the incident occurred in May while the excavator operator was preparing to load a haul truck at a bench area of an open-cut coal mine. The operator noticed the machine’s superstructure tilting to the left and attempted to reposition it.
During the manoeuvre, the excavator’s superstructure completely separated from the track frame after the lower mounting bolts on the slew ring bearing failed. The left-hand side of the superstructure fell to the ground, while the front right-hand corner came to rest on the left track.
The operator was able to exit the machine safely and was not injured.
Following the investigation, the regulator reminded mine operators to ensure principal hazard management plans (PHMPs) covering mobile plant operation and maintenance are supported by mechanical engineering control plans that address risks to the structural integrity of equipment.
It also urged operators to ensure risk assessments consider the potential failure of structural components, with critical load-bearing parts identified and managed through appropriate design, inspection, maintenance and replacement programs in line with site procedures and original equipment manufacturer (OEM) requirements.
The regulator said mine sites should have procedures in place to identify, report, assess and rectify structural defects, damage or deterioration before equipment remains in service. Workers should also receive appropriate information, training and supervision to safely operate and maintain mobile plant.
The investigation also reinforced the need for mine operators to review and revise control measures and management plans following incidents involving structural failures to ensure lessons are captured and future risks are addressed.
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