Two workers were hospitalised, and another injured, after being exposed to a high pressure fluid release in October, a NSW Mine Safety report has revealed.
Maintenance activities on an excavator were being carried out by a work group of five people, including a leading hand, tradesperson and apprentices, on October 13, 2015.
According to the report, the leading hand had to leave the worksite, giving the apprentices certain tasks to carry out in his absence. Maintenance activities continued under the guidance of the tradesman and the excavator was isolated using the main single point isolation valve.
“One task was the replacement of a check valve in the excavator track tensioning circuit. It was assumed by the workers that the hydraulic circuit was isolated and all energy dissipated,” the report said.
“Upon unscrewing the fitting on the check valve there was a release of high pressure hydraulic fluid.
“The release of high pressures hydraulic fluid resulted in injuries to three people with two being taken to hospital for exploratory surgery.”
The NSW Department of Industry investigation identified the check valve on the hydraulic track adjuster circuit was isolated, however the stored energy was not dissipated. It also found the excavator’s accumulators were not drained and there was no hydraulic circuit diagram available on the job.
“Mine operators are reminded that effective isolation and energy dissipation is a critical risk control when working on high pressure fluid systems,” the report said.
The department recommended the following steps before working on fluid systems:
1) Isolation of energy
2) Locking of the isolation point
3) Energy dissipation of all circuits on the downside of the isolation valve
4) Verification (test for dead) that there is no residual pressure in the circuit.
It also recommended mine operators should:
1) Remind tradespeople of the potential for residual stored energy from accumulators and valves. Tradespeople should always dissipate the energy and verify the circuit is not pressurised before attempting to work on any fluid systems.
2) Where possible install pressure gauges in all hydraulic circuits to assist in verification that all stored hydraulic energy is dissipated.
3) Always review the manufacturer’s information regarding the safe method of repair or maintenance.
4) Ensure that tradespeople fully understand the procedure for the task and have schematics/piping diagrams readily at hand.
5) Verify competencies for the task.
6) At all times provide adequate mechanical supervision of apprentices, when carrying out maintenance activities.