During the summer of 1997 a 36-year-old employee for a crane service company was killed while working on top of a portable tower crane. The crane was set up at a large wind farm, to assemble a large wind turbine. The crane was positioned adjacent to the metal column for the windmill and the outriggers were extended. The two-man crew from the crane company was preparing to place a 20-ton generator on top of the 140-foot windmill column while installation workers from the windmill company were inside the column ready to attach the generator with large bolts. The victim was working on top of the crane platform charging a battery for the winch engine on the crane, which had recently stalled. Suddenly, in a shower of hydraulic oil from the base of the crane, the right outrigger slid off its footing and the entire tower crane, extended to its maximum height of approximately 180 feet, fell to the north, away from the windmill tower, and crashed to the ground, carrying the wind generator and the victim with it. The victim rode with the crane to the ground and was killed instantly when he hit the ground. There was no wind that day, for other windmills were not operating. The farmer who owned the wind farm was standing at a safe distance, perpendicular from the line of the fall, and witnessed the entire event. The outrigger that failed was setting on fresh, packed dirt immediately adjacent to the new footing for the windmill column. It is assumed that this dirt caved in allowing the outrigger to slide off its base. Recommendations based on our investigation are as follows: 1. Portable tower cranes must be set up with extreme care to ensure that all outriggers are on solid ground with no potential for shifting or settling. 2. Workers must be diligent to regularly check and re-check alignment of crane equipment according to manufacturer's guidelines. 3. Additional means to anchor or secure tower cranes should be considered. 4. Employers should ensure that all equipment is in good operating condition. 5. Further safety engineering research should be conducted to determine whether this type of crane is adequately stable.
Region-7; Accident-analysis; Accident-prevention; Accidents; Injuries; Injury-prevention; Traumatic-injuries; Work-operations; Work-analysis; Work-areas; Work-performance; Work-practices; Safety-education; Safety-equipment; Safety-measures; Safety-monitoring; Protective-measures; Farmers; Equipment-design; Equipment-reliability; Construction-equipment; Construction-industry; Construction-workers