At a large coal mine a plug of up to 4% firedamp passed through a booster fan when a gas fast heading on the intake side of the booster was degassed in an uncontrolled manner. The auxiliary forcing fan to the heading was restarted by an electrician who had been sent to restore power to monitoring equipment. The incident could obviously have had very serious consequences.
Investigation revealed that the auxiliary fan, which was sited on the return side of a new working face, had been turned off due to periodic firedamp levels in excess of 1.25% which had repeatedly tripped the fan's Cardowan protection.
The fan was stopped but not properly isolated.
At the time of the incident the fan had not run for over a week and firedamp had built up in the heading. The fan had not been isolated and inspection reports had failed to highlight the deteriorating situation in the heading.
The Main Points to note are:
Yours sincerelyS P Wing