Fatality Assessment and Control Evaluation (FACE) Report for Colorado: Oil Field Worker Killed When Pressure Relief Valve Broke Off from Pump and Struck Victim in the Back of the Head

摘要

On September 15, 1989 an oil and gas field service company was preparing a natural gas well for operation. The operation being performed involved a high pressure test of a new well. Water is pumped, into the well casing, under high pressure to determine the integrity of the concrete casing. While assembling the required equipment an employee noticed that a pressure gage was defective. The operator of the pump stated that the gauge had worked the last time it was used and to install it. The pump being used was capable of providing in excess of 2000 pounds static pressure. A pressure relief valve was installed on the equipment by the rental firm that supplied the pump. At approximately 1400 hours the operation was started. When the pressure in the well reached 600 pounds the pressure gauge failed and no record of pressures reached was available from that point on. The engine on the pump started to bog down and the operator shifted into first gear and continued to pump for approximately one to two more minutes. At that time the piece of welding rod being used as a shear pin in the pressure relief valve sheared off. When the valve popped open the pressure relief valve assembly separated from the pump and struck the victim in the back of his head just below his hard hat. The pressure developed by the pump operating in first gear is in excess of 1500 pounds. Examination of the pressure relief valve assembly revealed that the connecting nipple was only screwed in three threads. When the valve released the internal gate slammed open and the shock created by that action stripped the connecting threads.