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District 8 - Coal Mine Safety and Health
Info-Grams and Close Call Accidents


Info-Grams
Close Call Graphic
Department of Labor
Mine Safety and Health Administration

Accident Info-Gram
January 2009

Equipment Run Over Cable; Shocks Miner

On January 22, 2009, at approximately 11:18 AM an electrical shock accident occurred at a District 8 coal mine. The accident occurred where a contract driller was drilling a return airshaft. A Caterpillar Model 325 track-hoe crossed a 12,470 high voltage cable and this damaged the cable. At this time, an employee on the West side of the drill rig received an electrical shock. The employee was standing next to the drill rig on the ground with his hand in contact with the drill rig.

Drill and Person

The location where the track-hoe crossed the cable was on the northeast side of the drill rig. A 2-inch by 6-inch board and a 2-inch by 10-inch board, covered with a sheet of plywood, were used to make a cable crossing. The crossing point was also on a grade, and when the track hoe crossed the high-voltage cable, the track hoe, boards, and plywood slid on the cable. This damaged the outer insulation on the cable, slid the shielding back on one phase conductor, and damaged the inner insulation on one phase. This damage resulted in a phase-to-ground fault on the cable.

Cable and Loader

Various locations where the injured person was reported to be working were checked, and all were found to be properly grounded. The 7200 VAC phase-to-ground current flowed from the cable into earth via various return ground paths. This exposed the victim to a voltage differential between the frame of the drill rig and the earth, which resulted in an electrical shock. The ground fault relay caused the circuit breaker protecting this high voltage circuit to de-energize the circuit in ½ second (47% of one cycle). This limited the victim's exposure time to the voltage differential.

The individual did not receive any burns from the electrical shock, and witnesses stated that the injured person's right hand and right leg were drawn. The victim was sent to the hospital for observation, released, and returned to work after two days.

BEST PRACTICES

  • " When it is necessary for equipment to cross high voltage cables, protect the cable from damage by hanging or using proper cable crossing methods

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This file was last updated on 02/26/2009

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.