An incident in January in which a gas ignition at the coal face at a coal mine in NSW on 23 January 2018 could have injured many, or worse, deadly, says the NSW Resources Regulator.
A safety alert issued by the regulator says that “if ventilation quantities are insufficient to prevent a methane layer from forming, and this layer goes undetected, an incendive spark can ignite the gas and if the flame path reaches an accumulation of methane in the general body, it can explode with devastating consequences”.
“Based on information provided by mine workers, the flame width was 2 m to 2.5 m (half width of cutter head) and came back over the head of the machine for 2m to 2.5m.),” the alert stated.
The regulator identified the following issues:
- The mine did not have a frictional ignition management plan
- The ventilation system in the panel was not at an acceptable standard, with vent rubbers missing and numerous vent tubes damaged
- Fan and vent tube sizing was marginal to ensure adequate ventilation at the face to dilute accumulation of gas
- The mine ventilation control plan did not stipulate requirements for supervisors to verify ventilation quantities at the face
A prohibition notice was issued in January preventing all workers from entering the site’s underground workings, except those undertaking safety-related activities.
The Resources Regulator recommends assessing frictional ignition risks at each mine and implementing effective control measures.
“Where incendive rock and methane gas are identified as a hazard, frictional ignition should be treated as a principal hazard and a principal hazard management plan developed,” the regulator says.
It also recommends ensuring that air quality, quantity and velocity at each working place is enough to prevent formation of methane layers and be capable of removing and rendering harmless, accumulations of methane gas.
The regulator says cutter picks should be inspected before every cutting cycle and changed as needed.
“Cutter pick beds and heads should be designed with water sprays arranged to prevent incendive sparking.”
“Continuous miners should have methane sensor heads positioned to maximize the likelihood of detecting gas and, in order to protect against frictional ignition risks, have a dedicated methane gas sensor that trips power to the cutter head located at, or close at, or close to, the cutter head. Operators are reminded that where electric cutter motors are positioned close to the cutter head, electrical trips to the cutter head should also be set at 1.25%.”
“Continuous miner operators and supervisors should be trained in frictional ignition risks and how to detect and prevent methane layering. This should include providing operators and supervisors with methanometers and supervisors with methanometer extension probes of sufficient range to enable tests for gas layers at the cutting face from a position of safety under supported ground.”
In response to the incident, the mine had established additional controls in place to address safety issues, while investigations continue.