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Significant Incident Report: No 6 / 2007

Minerals and Petroleum Regulation Significant Incident Report No 6 / 2007

ELECTRICAL CABINET EXPLOSION

INCIDENT

A routine service and inspection was being conducted on an underground drilling "jumbo" in the surface workshop of an underground gold mine. The machine was connected to 1000 volt power supply to facilitate the service.

An electrician conducting the service was leaning across the front of the machine mounted cabinet and depressing the stop button on the door when the doors were blown off the cabinet hinges and the cabinet deformed. He received a dislocated finger, lacerations to his chin and elbow as well as bruising to the abdomen from the impact of the door.

COMMENTS

  • The drilling rig was brought to the workshop.
  • Installation resistance and earth continuity tests were carried out on the rig and trailing cable.
  • The switchboard cabinet was cleaned out, using "CRC - Aerosol Contact Cleaner" which was sprayed into the base of the cubicle.
  • Approximately 5 minutes later the cabinet was closed.
  • The trailing lead was plugged in and the power turned on to the cabinet.
  • Approximately 30 minutes after the cabinet was closed the start button was pushed to operate the pump outlet and the outlet was tested for phase sequence.
  • The stop button was pushed and an explosion occurred.
  • An investigation by Energy Safe Victoria determined that there had been no electrical fault, but that fumes from the cleaning product had been ignited by a small spark produced when pressing the stop button .

RECOMMENDATIONS & PREVENTATIVE ACTION

  • Some cleaning products can produce an explosive atmosphere if used in confined spaces or if insufficient time is given for vapour to dissipate after use.
  • Before using any cleaning product all labelling details and warnings should be clearly understood and followed.
  • The appropriateness of cleaning products in specific applications should be reviewed.

FURTHER INFORMATION

  • Minerals Industry Safety Handbook. (Available from the Oeparlment).
  • Occupational Health and Safety Act 2004.
  • Energy Safe Victoria

PHIL ROBERTS

Director, Minera ls and Petroleum Regulation