DCP MIDSTREAM

Incident Narrative

ON MAY 20, 2015 AT APPROXIMATELY 6:30 PM, DCP WAS DELIVERING TO A CUSTOMER WHO HAD OPERATIONAL ISSUES AND BACKED UP PRESSURE TO DCP'S THREE RIVERS METER SKID. THE SHUTDOWN VALVE ESD 100 WENT CLOSED AT ITS SET POINT FOR OPP OF 1350 PSIG. AN NGL TECHNICIAN RESPONDED ON SITE AT APPROXIMATELY 7:30 PM AND DIVERTED FLOW TO AN ALTERNATE CUSTOMER. ANOTHER NGL TECHNICIAN WAS CALLED TO THE SITE FOR ASSISTANCE AND ARRIVED AT APPROXIMATELY 9:00 PM. WHEN THE TWO TECHNICIANS WERE READY TO LEAVE AT 10:10 PM, THEY NOTICED THE DOWNSTREAM SIDE OF A RELIEF VALVE WAS ICED OVER. THE RELIEF VALVE WAS DISCHARGING THROUGH THE VENT SYSTEM WHICH IS CONNECTED TO THE PLANT (CUSTOMER) FLARE. THE RELIEF VALVE WAS STUCK IN THE OPEN POSITION, SO THE TECHNICIAN THEN ISOLATED AND CLOSED PSV 200. AFTER REVIEWING DATA TRENDS, IT WAS DETERMINED THE RELIEF VALVE HAD OPENED AND DID NOT RESEAT. THE ESTIMATED TIME FRAME THAT THE RELIEF VALVE WAS DISCHARGING IS APPROXIMATELY 4 HOURS. THE ESTIMATED VOLUME THAT WAS RELEASED IS APPROX. 770 BBLS. THE RELIEF VALVE WAS REPLACED ON MAY 22, 2015. THE RELIEF VALVE THAT MALFUNCTIONED IS BEING SENT TO THE VENDOR FOR A FAILURE ANALYSIS. VENDOR ANALYSIS ON 6/17/2015 CONCLUDED THAT THERE WAS A PIECE OF WELDING SLAG BETWEEN THE DISC AND NOZZLE SEAT. THIS WOULD ACCOUNT FOR THE VALVE FAILING TO RESEAT. THE SOURCE OF THE WELDING SLAG IS UNKNOWN.