Abstract: A non-fired pressure vessel was brought back on line after it was cleaned and a new filter was installed. Employee #1 was operating the valves when a problem with one of the valves occurred. He moved to the front of the vessel. A coworker, another of the maintenance personnel, was opening the valve. As the pressure was nearing the operating pressure of 750 psi, Employee #1 noticed a leak around the cover and gave the coworker a signal to shut off the valve. The cover blew off, apparently striking Employee #1 near the lower left rib cage and knocking him approximately 65 ft before his body came to rest. His head was fractured and he was killed. The cover traveled some 45 ft, struck another vessel, and ricocheted another 65 ft before striking another vessel and coming to rest. The force of the fluid removed all of Employee #1's clothing. Oil and gas covered the coworker beside the vessel but he was not injured. A 60 ft radius around the vessel was also covered with oil.