Inspection Detail

Inspection: 1152990 - Minnotte Constructing & Erection Corporation

Inspection Information - Office: Charleston Area Office

Investigation Summary

A CARPENTER WAS DRILLING A HOLE IN A METAL DOOR CASING TO MOUNT 4-INCH METAL HINGES. HE WAS USING A 3/8-INCH-DRIVE, METAL-CASE ELECTRIC DRILL. THE EMPLOYEE WAS STANDING IN A DOORWAY, WITH HIS LEFT FOOT ON A CONCRETE SURFACE AND HIS RIGHT FOOT ON A METAL-GRATE STAIRWAY LANDING. THE EMPLOYEE WAS LEFT HANDED. IT IS BELIEVED THAT HE HELD THE ELECTRIC DRILL IN HIS LEFT HAND AND HELD THE METAL STAIR RAILING (TO THE RIGHT OF THE DOOR) WITH HIS RIGHT HAND. THE ELECTRIC DRILL HAD A 3-CONDUCTOR, 6-FOOT FLEXIBLE CORD BETWEEN THE GROUNDING-TYPE ATTACHMENT PLUG AND THE DRILL. THE DRILL WAS CONNECTED TO A 3-CONDUCTOR TEMPORARY LIGHTING CIRCUIT, WHICH IN TURN WAS ENERGIZED BY A STANDARD 3-CONDUCTOR, ROUND, EXTENSION CORD SET. THIS CORD SET WAS PLUGGED INTO A PERMANENT, 120-VOLT, 20-AMPERE RECEPTACLE. THE MOLDED ATTACHMENT PLUG ON THE EXTENSION CORD SET HAD ITS GROUNDING PRONG REMOVED. IN DARKNESS, THE CARPENTER INSERTED THE ATTACHMENT PLUG INTO THE PERMANENT RECEPTACLE IN A REVERSE POLARITY POSITION. THIS CAUSED THE UNGROUNDED CIRCUIT CONDUCTOR TO BE CONNECTED TO THE GROUNDED POLE OF A STANDARD SINGLE-PHASE, THREE-WIRE CIRCUIT. A GROUND FAULT PERMITTED THE ELECTRIC DRILL CASE TO BECOME PART OF THE CIRCUIT THROUGH THE IDENTIFIED GROUNDED CONDUCTOR (WHICH WAS CONNECTED TO THE UNGROUNDED CONDUCTOR AT THE POINT OF REVERSE POLARITY). THERE WAS NO EQUIPMENT GROUNDING CONDUCTOR TO PROVIDE A PATH TO GROUND. WHEN THE EMPLOYEE, WHO WAS HOLDING THE DRILL, GRABBED THE METAL STAIR RAILING, HIS BODY COMPLETED THE ELECTRIC CIRCUIT TO GROUND. THE EMPLOYEE COLLAPSED; THE ENERGIZED DRILL LANDED ON HIS CHEST; AND HE WAS ELECTROCUTED.

Keywords: ELECTRICAL, REVERSE POLARITY, CORD SET, ELECTROCUTED, ATTACHMENT PLUG, E C, GROUND FAULT, EQUIPMENT GROUNDING, ELECTRIC DRILL