Electrical Flash Burn Fatally Injures Mechanic

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Ronald J. Panunto, PE, CFEI ::::

Case Synopsis: An electrical maintenance mechanic at a dairy plant died from electrical flash burns while troubleshooting an inoperable 480VAC motor. Expert was retained by dairy plant management to determine whether or not there was a defect in the switchgear and if the mechanic followed proper safety procedures.

Expert Analysis: An inspection of the 480 volt switchgear, and of the damaged fused switch, showed that the electrical equipment functioned properly. An interview with a fellow worker, who was with the injured mechanic, indicated that the mechanic had determined that the motor was not working due to a blown fuse. The mechanic manually bypassed the switchgear safety lock and attempted to replace the blown fuse with the feeder still energized, and the motor still connected. When he plugged in the new fuse, the starting current from the motor caused an arc, which then promulgated to a bus fault from the energized feeder and fatally injured the mechanic. An inspection of the switchgear showed that the fuse compartment could not be opened with the feeder switch energized. The fuses are protected with a safety interlock. The only way that energized fuses could be contacted, was if the safety interlock had been purposely bypassed by the mechanic. This was confirmed by his coworker. A review of the mechanic’s training record showed he was trained in lockout/tagout procedures, and that he had been instructed never to work on energized circuits.

Result: Video presentation showing that the switchgear’s safety interlock prevented the fuses from being accessed, unless purposely bypassed, was shown at an arbitration hearing where a favorable settlement for the dairy plant resulted.

 

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