Abstract: At approximately 3:00 p.m. on November 2, 2002, Employee #1, an oiler working for Maxim Crane Works, was working at a customer's steam methane reformer. At the time of the accident, a used preheater was being set on cribbing with a 350-ton crane and a 266,000-pound crane. As the preheater was rotated from a vertical to a nearly horizontal position, the lifting pads that held up one end popped off the preheater. That end of the preheater dropped to the ground. At that time, Employee #1 was placing a piece of wooden cribbing under that end of the preheater. The preheater dropped onto the end of the timber further from the employee, jerking the near end of the timber out of the employee's hands. As the near end was propelled to the ground, it struck the employee's right femur, causing a compound fracture. The employee was hospitalized with his injuries. Inspection of the bolts that held the lifting pads to that end of the preheater revealed that 22-millimeter-diameter nuts had been used with 20-millimeter bolts. As the preheater was set down from a vertical to a horizontal position, the load on the bolts changed from shear to tension. Under tension, the threads could not sustain the load, and the bolts pulled out of the nuts. The lifting pads, bolts, and nuts that failed had come into the facility attached to the replacement preheaters. Other employees had removed them from a new preheater and used them to rig the old preheater. After hand tightening, the fasteners were secured with crescent wrenches. The improper fit between the nuts and bolts was not detected by either employee. Both employees were experienced in the use of fasteners. Inspection of the new preheaters revealed that some lifting pads were secured with properly sized bolts and nuts while other pads had mismatched bolts and nuts.