ONEOK NGL PIPELINE, LLC

Incident Narrative

OPERATOR'S INSTRUMENTATION TECHNICIAN WAS ATTEMPTING TO CALIBRATE PRESSURE TRANSMITTER AT LOCATION. THE ROOT VALVE (NEEDLE VALVE) THAT CONNECTS THE INSTRUMENTATION TO THE PIPELINE WAS CLOSED AND CONNECTION TUBING (1/2"" DIAMETER) DEPRESSURIZED. AFTER THE TECHNICIAN REMOVED THE TUBING FROM THE PRESSURE TRANSMITTER, TUBING WAS STILL CONNECTED TO ROOT VALVE, IT IS BELIEVED AN ACCUMULATION OF ICE RELEASED FROM THE INSIDE OF THE TUBING ALLOWING PRODUCT TO RELEASE. TECHNICIAN ATTEMPTED TO FURTHER TIGHTEN THE ROOT VALVE IN AN ATTEMPT TO ISOLATE THE RELEASE BUT THE VALVE HANDLE BROKE AND HE WAS UNABLE TO ISOLATE THE TUBING. IT IS BELIEVED THERE WAS AN ACCUMULATION OF A FOREIGN MATERIAL WAS BETWEEN THE NEEDLE AND THE VALVE SEAT WHICH PREVENTED THE VALVE FROM FULLY CLOSING. TO ISOLATE THE FAILED ROOT VALVE, A SECTION OF PIPELINE BETWEEN THE STATION FIRE VALVES WAS ISOLATED AND PRODUCT WAS ALLOWED TO VENT TO THE ATMOSPHERE UNTIL THE SECCTION DEPRESSURIZED. ONCE THE ISOLATED SECTION WAS COMPLETELY DEPRESSURIZED THE ROOT VALVE WAS REMOVED AND REPLACED WITH A NEW VALVE. ONEOK INSTALLLED A NEW STYLE OF PRESSURE TRANSIMITTER AT THE LOCATION THAT IS CONFIGURED WITH REDUNDANT VALVING TO ALLOW DEPRESSURIZATION OF THE TRANSMITTER FOR REPAIR OR REPLACEMENT. THE ONEOK EMPLOYEE AND HIS SUPERVISOR REVIEWED THE PROCEDURES FOR INSPECTING THE TRANSMITTER AND DETERMINED THE PROCEDURE TO BE ADEQUATE.