Material in the intrusion was much harder than the coal, resulting in increased wear on the shearer and picks. The operator did not notice the damage to the cutting equipment, the inspectorate said.

The possible consequences of continued cutting with damaged equipment were not identified and the management direction to the crew – that is, to continue cutting to position the shearer at the maingate for maintenance – was not communicated to the coal mine deputy.

There was also poor communication of, and lack of adherence to, the drum pick inspection regime, according to the Mines Inspectorate report.

“Mine management had previously identified hazards when mining through the hard rock intrusion,” chief inspector of coal mines Gavin Taylor said in the report.

“The shearer had been fitted with specialised drums to suit the changing conditions, and heavier bodied picks had been sourced and fitted for cutting the intrusion. Fortunately, in this incident, methane levels were insufficient to fuel an ignition.”

The Mines Inspectorate has recommended that mines quantify the inspection regime and monitor use of inspection sheets, records of inspections and records of any damaged equipment changed out.

Also, before intersecting intrusions, mines should conduct longwall crew training on additional hazards expected and ensure the appointed ERZ controller is on the longwall face during intrusion intersection.

Mines should also implement appropriate controls for mining through methane drainage holes and conduct face-to-face handovers, the inspectorate said.