Department of Labor
Mine Safety and Health Administration
Electrical Arc Shocks Maintenance Foreman
On January 16, 2003, a potential fatal electrical accident occurred at an underground mine in District 8. A Maintenance Foreman contacted energized 995-volt conductors inside of a controller enclosure on a Joy continuous miner. He spent one night in the hospital. His only injury was a small cut on his right index finger.
Malfunctioning for several shifts, the Joy continuous-miner's scrubber motor had been "dropping-out" intermittently, causing the cutter head to shut off. Near the end of the day shift, the Maintenance Foreman and the Section Mechanic decided to open the main (left-side) controller enclosure to repair the problem. The Maintenance Foreman instructed the Miner Operator to trip the main circuit breaker on the miner. The Miner Operator inadvertently de-energized the control and light circuit breaker. The Maintenance Foreman removed the arc chute from the scrubber-motor line starter. He was using a screwdriver to inspect the scrubber-motor line starter when an electrical arc occurred, and the Maintenance Foreman received an electrical shock.
The qualified Maintenance Foreman failed to de-energize, lock, and tag the power supply circuit to the continuous miner before removing the main-controller enclosure cover. His performance of electrical work on an energized circuit resulted in a near miss accident that could have easily caused a fatality.
- The qualified electrician doing the work must ensure that equipment is de-energized, locked and tagged out.
- Troubleshooting and testing energized circuits must be performed only when the purpose is to determine voltages and currents and does not include the repair of the electrical problems.
- Gloves, in accordance with §75.1720(c), are required whenever qualified persons troubleshoot or test energized electric power circuits or electric equipment.
- Lock out and tag equipment power supply circuits before removing controller enclosure covers.
This information was provided by concerned miners in an effort to eliminate accidents. Accident or "close call" information within District 8 may be shared by contacting
the MSHA office at (812) 882-7617.