In May 2018, workers were exposed to potentially serious or life threatening injuries when disassembling a haul truck's hydraulic accumulator.
The truck’s accumulators had been depressurised during the day shift and a fitter was required to remove the pistons and replace the seals. The night shift fitter referred to the site-specific procedure for the task, but it deviated from the original equipment manufacturer's (OEM's) procedure and the particular configuration the fitter was working on was not covered.
Upon realising that the procedure did not cover the configuration, the fitter sought advice from other workers, including the shift supervisor, who was not available. He received conflicting advice. He was not advised to stop the task.
The fitter re-installed the accumulator’s cap and applied a controlled use of compressed air to lift the pistons, but could not get all the pistons to move. He then tried removing the accumulator’s cap, but it would not release. The fitter used high tensile bolts in the cap to secure it and a pry bar to distance himself from the accumulator. The cap and piston ejected suddenly, narrowly missing him and hitting the raised tray of the truck, before landing near another worker several metres away.
Direct causes
The correct procedure for disassembling the accumulator configuration was not followed, resulting in an uncontrolled release of energy.
Contributory causes
Inadequate training and supervision
- The fitter was new to the task. He had insufficient knowledge, training or experience to perform the work assigned to him.
- He was not supervised while undertaking the task.
Inadequate procedure
- The site-specific procedure deviated from the OEM's.
- The site-specifc procedure did not cover all the variations of accumulator configurations, and the configuration the fitter was working on was not covered by the procedure.
Inadequate safe systems of work
- Work planning and scheduling failed to apply good risk management practices, including skills identification and the need for supervision.
- A comprehensive risk assessment was not carried out for the task (e.g. job hazard analysis, JHA) and the potential for exposure to hazardous energy was not identified.
- The site’s change management process did not address the hazards and risks introduced when deviating from the OEM procedure.
- Co-workers did not exercise duty of care and intervene to stop the fitter undertaking the task.