Case Synopsis: An accident occurred when an electrician and his helper attempted to hoist a transformer into position. Two men secured the transformer to lifting forks before the electrician turned the crank. On the first attempt, the material hoist raised the transformer several feet before it became stuck. The electrician saw that the mast sections were not telescoping and recognized that there was a problem, so he asked his foreman for help. The foreman turned the crank and attempted to lift the transformer, but the material hoist became stuck again, so he called the equipment rental company and asked for assistance. A rental company technician told the foreman to expect resistance and advised him to continue cranking the handle. With substantial effort, the electrician eventually raised the transformer until it was almost in its final position. The mast sections unexpectedly separated from the base of the hoist as the electrician was cranking the winch handle. The transformer fell and injured the foreman.

Expert Analysis: Design, operation, and maintenance of the material hoist were evaluated to determine the cause(s) of the accident. Disassembly revealed several problems that prevented the material hoist from functioning properly, including a frayed hoist lift cable; a portion of the cable jammed between a pulley and mast section; a seized pulley bearing, and inadequately lubricated pulleys and rollers. Engineering analysis determined that the construction equipment rental company did not inspect and maintain the material hoist in accordance with requirements in the manufacturer’s operating and maintenance manual. The cumulative effect of inadequate inspection and maintenance by the rental company prevented the material hoist from operating properly and caused the mast sections to separate while it was lifting the transformer.

Result: Engineering analysis concluded that the material hoist was in defective condition when the rental company delivered it to the job site. Problems caused by material hoist deficiencies were exacerbated by incorrect advice provided by the rental company technician. The operating manual specifically warns users not to operate the material hoist if the mast sections are not moving freely. The rental company technician should have advised the foreman to stop operating the material hoist. Instead, he instructed the foreman to continue cranking the winch handle after the material hoist was stuck.