Abstract: Employees #2 and #3, outside contractor personnel, were observing and testing recently deposited welds inside an 8 ft diameter by 24 ft long steel pressure vessel. Employee #1 was entering the vessel through a 20 in. diameter manway to grind a weld at the request of one of the two outside contractor personnel. An explosion occurred within the vessel and the force of the explosion propelled Employee #1 approximately 27 ft into a stationary steel cabinet, causing severe injuries that resulted in his death. Employees #2 and #3 were severely burned and were hospitalized. The introduction of lpg (possibly propane) into the tank from an unmarked piping system and hose, and at the same time, the activation of an ignition source (possibly an electric drop-light or the flash from a cigarette lighter) caused the explosion. The vessel manufacturer had a thorough confined space entry/work procedure that had not been implemented at this plant.