Abstract: At 3:30 p.m. on December 8, 2002, an accident took place in Unit 44, the heavy oils light ends recovery system, in a large oil refinery in Wilmington, Delaware. This unit used process of absorption and distillation to recover butane and propane from the sour overhead gas streams in the cooker unit and the vapor recovery unit. The accident took place at the bottom of 44-V-4004, a debutanizer that separated the butane and then the propane from the naphtha for further processing. 44-V-4004 was out of service and being steam cleaned for about 24 hours. Employee #1, a chief operator, and a coworker went out to the approximately 120-ft-high by 8-ft-round vessel to discuss the next phase of the cleaning process. Employee #1 and the coworker blocked in a 2-in. valve venting steam to the Process Depressuring System (PDS) and broke the flange below a 4-in. valve, installing spreader bars between the flanges. This piping configuration was approximately 6 ft above the deck. The steam to the tower was restarted and the valve above the spreader bar flange was opened, steaming the vessel to the deck. At 3:30 p.m., Employee #1 and the coworker went to the vessel and removed the steam and water. Employee #1 went to the spreader bar flange to verify that 44-V-4004 was empty. Employee #1 picked up a piece of a wire, Number 9, and probed between the spreader bar and the flange to dislodge any scale. As Employee #1 turned, a hot condensate gushed out of the spread flange, knocking him to the ground. Employee #1 sustained second-degree burns to the back, arms, and legs and was hospitalized.