On March 25, 2003, two employees working for an power generation facility were instructed to remove a cover plate from an electrical generator. The hydrogen gas had been purged from the generator and replaced with air pressurized at approximately 40 psi. The generator was pressurized with air so that the workers could perform a leak test on the system. The cover plate was 11.5 inches thick and 19 inches in diameter. It was secured to the generator by 24 bolts, which were 21.5 inches long by 0.625 inches in diameter. The two employees were informed that the cover plate needed to be removed so that a balancing weight could be removed from the shaft. It would be used as a guide to manufacture additional weights.