ONEOK WESTEX TRANSMISSION, LLC

Incident Narrative

ON 2 MARCH 2017 AT 15:45 P.M. MAINTENANCE CONCERNS REGARDING FILTERS AT THE RECENTLY CONSTRUCTED WICKETT II TURBINE COMPRESSOR STATION PROMPTED AN INSPECTION, DURING WHICH A CONSTRUCTION INSPECTOR CLOSED THREE VALVES TO FACILITATE THE MAINTENANCE INSPECTION. THE VALVE CLOSURES RESULTED IN ISOLATING THE GAS SUPPLY LINES THAT SUPPLIED THE ACTUATOR FOR THE SUCTION PIPING ESD VENT VALVE. A PRESSURE REGULATOR ON THE GAS SUPPLY LINE ASSOCIATED WITH THE SUCTION PIPING ESD VENT VALVE SUBSEQUENTLY MALFUNCTIONED CAUSING THE VENT VALVE TO FAIL OPEN AT APPROXIMATELY 19:53 P.M. THE CONTROLLER OBSERVED THE SCADA ALARM AND ACKNOWLEDGED THE EVENT IN THE SYSTEM BUT HE FAILED TO RECOGNIZE THE POTENTIAL CAUSE AND MISINTERPRETED THE ALARM. HE DID NOT CALL OUT ANY FIELD EMPLOYEES TO INVESTIGATE THE CAUSE OF THE ALARM AND SUBSEQUENTLY, 69,217 MCF OF GAS VENTED TO ATMOSPHERE. THE VENT REMAINED OPEN UNTIL AN EMPLOYEE ARRIVED ON LOCATION AT 06:30 A.M. ON 3 MARCH 2017. AT APPROXIMATELY 06:58 A.M. THE EMPLOYEE RESTORED PRESSURE TO THE GAS SUPPLY LINES AND CLOSED THE VENT VALVE STOPPING THE VENTING OF GAS. IN THE IMMEDIATE AFTERMATH OF THE INCIDENT DIFFICULTY IN DETERMINING THE START TIME OF THE VENTING WAS THE PRIMARY CAUSE OF THE DELAY FOR DETERMINING THIS RELEASE EXCEEDED 3,000 MCF. TO CORRECT THE SITUATION OPERATIONS PERSONAL HAVE AUGMENTED THE LOGIC OF THE PLC SYSTEM TO ESD THE ENTIRE STATION WHEN EITHER THE DISCHARGE PIPING OR SUCTION PIPING ESD VENT VALVES OPEN FOR ANY REASON.