scope:

Description of Driving Event:

During a crane disassembly, a cable sling broke, dropping a 10 ton crane counterweight. The crane crew was removing the front counterweight from the crane to place it on a flat bed trailer when the mishap occurred. The sling used was a rusty, 4 leg, 5/8 inch diameter cable about 15 feet long. Only two legs were used during this lifting operation.

The investigating committee found that calculations made from a standard table published by U.S. Steel showed that the allowable working load for a new cable of this size using 2 legs was only 5.28 tons. The crane operators, based on their experience and intuition, grossly underestimated the strength of the sling.