Abstract: On February 14, 1991, Employee #1 and coworkers on the night shift at Energy Coatings Company, were jacking up a 3,300 lb self-propelled rail pipe cart that had been driven into a 2 ft deep pit. They were using an electrical pumping unit connected by a pressure hose to a 30-ton jack. The lifting was done in 2 in. increments, and blocks and shims were used to support the cart when it was not on the jack. The crew had made two or three lifts when the jack operator turned on the pumping unit to again raise the cart. When there was enough clearance to place a shim, Employee #1 told the coworker to stop the pump and he started to put in the shim. When the pump stopped, the jack came down and the cart crushed Employee #1's left thumb. The injury necessitated the amputation of half of Employee #1's thumb. The accident resulted from the design of the pumping unit because the motor is capable of moving more oil than can be passed by the relief valve. Even with the relief valve open, as it was when the accident occurred, the pump could raise the jack, but when the motor was shut off, the jack descended immediately. The relief valve needed to be redesigned.