The NSW Resources Regulator recently issued a safety alert about the risk of serious injury and potential death to maintenance workers as a result of high-pressure fluid releases, following a number of incidents in which workers sustained injuries after being struck in the face and body.
The incidents involved experienced contract maintenance workers undertaking a variety of tasks on hydraulic systems, and high-pressure fluid release was not an intended outcome of the task.
The hierarchy of controls relied upon to control high pressure fluid release failed to prevent the maintenance workers from being struck and injured in several incidents over recent months.
The first incident involved a longwall changeout, in which a contract maintenance worker isolated a roof support and checked the pressure gauge on the maingate leg which appears to have indicated zero pressure.
The worker then loosened retaining bolts on the double check valve on the roof support leg, and the stored pressure in the support leg released and tore the workers shirt and caused abrasions to his chest.
The pressure gauge was later tested as operational; however, the cover was cracked. A face audit identified that three out of 680 pressure gauges on the longwall face were also incorrectly indicating zero pressure.
In another longwall changeout procedure, a maintenance worker restored hydraulic pressure to a set of 20 roof supports for removal. A power take-off plug had not been replaced on one roof support in the set of 20.
A release of high-pressure fluid occurred from a power take-off port when the roof supports were re-pressurised. The high-pressure fluid release put another maintenance worker at risk of being struck by the fluid.
The mine investigation identified that another power take-off plug was also missing on another support. However, that support had not been re-pressurised in the set of 20 supports.
In a third incident, a contract maintenance worker was performing live hydraulic pressure testing to obtain pressure decay data from a hydraulic hoist on a large haul truck.
The fitting connecting the hydraulic hose to the test meter released fluid under pressure and the worker was struck in the face by high pressure fluid.
In considering the circumstances of each of these events, the safety alert said it is apparent the hierarchy of controls to reduce the exposure of workers to high pressure fluid have not been applied effectively – in particular the elimination of the risk by failing to identify residual pressure, and to bleed this pressure off appropriately.
“It is apparent that the use of isolation barriers to disperse, deflect and diffuse fluids when an unintended release occurs have also not been effective,” the alert said.
“Isolation barriers could include temporary movable protective coverings and shielding devices that are located between the worker and the pressurised equipment during the task.”
The alert subsequently made a number of recommendations:
1. Mine operators should review the effectiveness and reliability of safety management system controls for risks associated with unintended release of high pressure fluids.
2. Mine operators should review isolation procedures to ensure effective isolation of hydraulic systems.
3. Mine operators should review the training and competency of workers undertaking high pressure fluid power system tasks.
4. Mine operators should review the specific exposure of workers undertaking high pressure fluid tasks, provide isolation barrier devices, and improve personal protection equipment standards to prevent high pressure fluid injuries.
5. Mine operators should review contractor management systems to ensure contract maintenance workers have appropriate competencies, are provided with reliable task related information and are supervised for compliance with the site’s safety management systems.