Abstract: The company, which reclaims scrap metal, was disassembling a heat exchanger at the time of the accident. Two employees were cutting the tubes from the heat exchanger with an acetylene cutting torch. The operator of the American crawler crane, model 797, with a magnet lifting head, attempted to roll the heat exchanger over so the two employees could cut the tubes without difficulty. As the operator started pulling sideways with the boom, the right boom seat pin came out and the boom fell approximately 90 degrees to the crane. It came to rest on top of the shaker building. The force of the falling boom caused the roof of the shaker building to collapse onto the shaker table. Employee #1 was standing on top of the shaker table and was struck by the roof. It appears that Employee #1 was killed instantly. By design, the boom seat pins are required to be secured in place with a bolt. However, these pins were tack welded in place. It appears the weld had broken or had not been adequately molded, allowing the pin to vibrate out of place. The pin on the left of the boom had also been modified and tack welded. The company stated that it had not obtained written permission from the manufacturer to modify the cranes. The company did state that the crane was in this condition when purchased.