TENNESSEE GAS PIPELINE COMPANY

Incident Narrative

"ON 10/16/2021 AT 21:59 EASTERN, GAS CONTROL RECEIVED A STATION WARNING ASSOCIATED WITH TENNESSEE GAS PIPELINE (TGP) STATION 264 AND IMMEDIATELY COMMUNICATED THE WARNING TO THE OPERATIONS TECHNICIAN ON CALL. AT THE SAME TIME, A NEARBY RESIDENT CALLED THE FIRE DEPARTMENT TO REPORT LOUD NOISE AND GAS SMELL IN THE AREA. AT 22:40, THE OPERATIONS TECHNICIAN AND THE CHARLTON FIRE DEPARTMENT ARRIVED ON SITE. THE OPERATIONS TECHNICIAN STARTED HIS INVESTIGATION AND FOUND GAS VENTING THROUGH A VENT VALVE ON COMPRESSOR UNIT 1C. AT 22:45 THE OPERATION TECHNICIAN MANUALLY CLOSED, THE 4"" VENT VALVE, ENDING THE EVENT. THE EVENT WAS DETERMINED TO EXCEED THE REPORTABLE THRESHOLD OF 3,000 MCF AND SUBSEQUENTLY REPORTED TO THE NRC. THE INTERNAL INCIDENT INVESTIGATION CONCLUDED THAT THE STATION WARNING OCCURRED BECAUSE UNIT 1C EXPERIENCED A FAILURE OF THE 120VDC/24VDC POWER SUPPLY THAT POWERS THE SOLAR PANEL, PLC AND ASSOCIATED I/O'S. THE PLC CONTROLS THE POSITIONS (OPEN OR CLOSE) FOR THE COMPRESSOR UNIT MANIFOLD VALVES. BECAUSE THE PLC POWER FAILED, THE MANIFOLD VALVES REMAINED IN THE LAST POSITION AND THE UNIT BLOWDOWN VALVE OPENED. THE UNIT WAS RUNNING AT THE TIME OF THE PLC FAILURE. THEREFORE, THE UNIT SHUT DOWN THE MANIFOLD VALVES AND THE BLOWDOWN VALVE REMAINED OPEN ALLOWING GAS TO VENT. IN ORDER TO PREVENT REOCCURRENCE AT TGP STATION 264, OPERATIONS WILL INSTALL A REDUNDANT POWER SUPPLY FOR UNIT 1C. IN ADDITION, OPERATIONS ISSUED AN INCIDENT FLASH FORM FOR DIVISION 10 TO EVALUATE COMPRESSOR STATIONS TO IDENTIFY UNIT MANIFOLD VALVES THAT DO NOT CLOSE OR UNIT BLOWDOWN VALVES THAT DO NOT OPEN UPON FAILURE OF UNIT PLC. THE REVIEW WILL IDENTIFY UNITS WHERE MODIFICATIONS ARE REQUIRED."