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A number of incidents and near misses have been recorded involving the installation and removal of longwall roof supports using temporary hydraulic lines, or whip hoses. Workers have suffered hand injuries after being hit by high-pressure hydraulic fluid at 350bar.
In a recent incident, workers were setting up longwall chocks on an installation face using whip hoses connected to an adjacent chock Power Take Off outlet. One worker isolated the hydraulic power in the whip hoses and released the pressure in the lines by opening the bleed line.
The hydraulic pressure was released in an uncontrolled state and the fluid hit the worker’s hand causing injury but fortunately was a near miss for fluid injection.
The subsequent investigation found there was no positive locking isolation device incorporated in the isolation of the hydraulic energy. The system and equipment used to connect the temporary hydraulic power to install supports was not supplied by the Original Equipment Manufacturer, nor was the OEM consulted on the design and operation of the equipment.
The DMR has made a number of recommendations for operators’ consideration. Among them: mines consult OEMs for the recommended procedures to install roof supports; review installation and recovery hoses for fit-for-purpose application; and ensure isolation valves are positive lockable type while the bleed valve (lockable type) should be capable of releasing the hydraulic pressure in a controlled state.
The DMR also said all procedures should include positive isolation instructions and the pressure line must be connected to the relative ports, and return line must be connected back to the tank at all times. The hydraulic system must have pressure relief in the event of over pressurisation and if possible reduce the installation pump pressure to activate the roof supports.
“Best practice is to interlock the isolation valve and the bleed valve so both valves cannot be open at the same time,” the DMR said. “Alternatively a system could be developed with the equivalent level of safety.”
