Two Workers Electrocuted when Boom Crane Contacts 7,200 Volt Overhead Power Line

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Type:  Report - Gov

Publisher:  Washington State Department of Labor & Industries, Olympia, WA

Published As:  Public


Topics:  Electrical, Occupational Safety and Health, Hoisting and Rigging, Hazardous Energy Control

On the day of the incident, a material handler rigged a propane tank with a metal chain so that it could be lifted by the crane. The tank was located at the end of a row of 320-gallon capacity tanks adjacent to a fence marking the yards boundary. Just beyond the fence, a 3-phase 7,200 volt overhead power distribution line, crossed over into the yard at a diagonal by a few feet at this location.

A service technician proceeded to position the crane boom for the lift. As he was doing so, the tip of the fully extended boom contacted one of the power line wires. Electrical current traveled down the boom to the truck and the metal grating of the crane operators station where the service technician was standing. He died instantly when he stepped from the station to the ground, with one foot on the station and one foot on the ground, thereby creating a pathway for the current to move from the crane through his body to the ground. The boom remained in contact with the power line, creating a constant flow of voltage through the crane to the ground. The intensity of the electrical current caused the trucks tires, nearby tanks, and adjacent ground to catch fire. The area where the material handler stood between two rows of tanks was about 28 feet from the truck. This area was not energized. He then went toward his coworker, presumably to provide aid, and entered the electrical field where he too was electrocuted.

To prevent similar occurrences in the future, Washington State Fatality Assessment and Control Evaluation investigators concluded that propane gas suppliers and other employers using cranes should follow specific guidelines. The guidelines are included in the attachment.

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