EL PASO NATURAL GAS CO

Incident Narrative

ON JULY 27, 2021 AT 20:30 (CST), THE EL PASO NATURAL GAS (EPNG), KEYSTONE COMPRESSOR (KC) STATION LOST COMMERCIAL POWER. AT THE SAME TIME, THE KC STATION EXPERIENCED HIGH INLET PRESSURE FROM LINES 3026 AND 1105. SINCE THIS IS A MANNED STATION, OPERATORS BEGAN CLOSING BLOCK VALVES ON THE 3026 LINE AND 1105 LINE IN ORDER TO ISOLATE THE COMPRESSOR STATION. THE 3026 LINE BLOCK VALVE (MLV 2) WAS THE FIRST VALVE CLOSED AT 21:20 PM, WHICH RESULTED IN THE ACTIVATION OF MULTIPLE RELIEF VALVES PV 13, PV 14 AND PV 15. ONCE THE PRESSURE RELIEF VALVES VENTED, THE NEXT STEP THAT WAS TAKEN WAS TO CLOSE THE 1105 LINE BLOCK VALVE (MLV 0). HOWEVER, ONE OF THE THREE PRVS CONTINUED TO VENT AND IT WAS DISCOVERED THAT THE VALVE SPRING WAS BROKEN AND FAILED TO RESET. THIS RESULTED IN THE 3026 AND 1105 LINE BEING VENTED FLAT AND A GAS LOSS OF 164 MCF. AT 21:24, THE 2-STAGE VALVE THAT KEEPS THE PLANT A DISCHARGE GAS CONTAINED OPENED DUE TO UTILITY AIR BLEEDING. THIS RESULTED IN THE PLANT A DISCHARGE FEEDING BOTH THE PLANT A AND PLANT B SUCTION LINES, WHICH RESULTED IN ACTIVATION OF PSV 45. AT 21:30 THE EMERGENCY RESPONSE LINE (ERL) WAS ACTIVATED AND THE INCIDENT WAS DEEMED REPORTABLE. THE 2-STAGE VALVE WAS CLOSED AT 21:53 AND COMMERCIAL POWER WAS RESTORED TO THE STATION AT 22:45. THE KC STATION RETURNED TO NORMAL OPERATIONS AT 00:00 AM. THE FIRST RELEASE POST-ACCIDENT INVESTIGATION REVEALED THAT THE ROOT CAUSE OF THE ACTIVATION OF PV 13, PV 14 AND PV 15 WAS CLOSING THE 3026 LINE BLOCK VALVE BEFORE CLOSING THE 1105 LINE BLOCK VALVE. IT WAS LATER DETERMINED THE 1105 LINE WAS HOLDING A HIGHER PRESSURE. THIS COUPLED WITH THE MALFUNCTIONING OF THE PRESSURE RELIEF VALVES RESULTED IN THE LOSS OF 164 MCF. SUBSEQUENTLY, THE RELIEF VALVES HAS SINCE BEEN REPLACED AND REPAIRED. CHANGES TO THE LOCAL STATION PROTOCOL REGARDING THE ISOLATION OF THE STATION WERE INCORPORATED IN ORDER TO IDENTIFY THE LINE WITH THE HIGHEST PRESSURE BEFORE STARTING THE ISOLATION PROCESS. THE SECOND RELEASE POST-INCIDENT INVESTIGATION REVEALED THE ROOT CAUSE OF THE PV 45 ACTIVATING WAS THE LACK OF UTILITY AIR TO THE 2-STAGE VALVE DUE TO LOSS OF COMMERCIAL POWER. THE 2 STAGE VALVE OPENING WAS THE CAUSE OF THE MAOP EXCEEDANCE RESULTING IN PV 45 ACTIVATION. PV 45 PROTECTS THE SUCTION LINE INTO BOTH PLANT A AND PLANT B. THE SUCTION LINE EXPERIENCED A PRESSURE OF 668 AND HAS AN MAOP OF 580. THE GAS LOSS DUE TO THIS INCIDENT WAS 6,396 MCF. THE 2-STAGE VALVE OPERATION HAS SINCE BEEN MODIFIED FROM AUTOMATIC TO MANUAL AND IS CURRENTLY TAGGED.