TENNESSEE GAS PIPELINE COMPANY

Incident Narrative

ON MAY 19, 10:40 PM LOCAL TIME, GAS CONTROL RECEIVED A CALL ABOUT A NOISE COMPLAINT ASSOCIATED WITH TGP'S COMPRESSOR STATION NO. 17 (I.E., CS 17). GAS CONTROL CALLED TGP OPS SPECIALIST WHO ARRIVED ON SITE AT 10:44 PM LOCAL TIME TO INVESTIGATE THE NOISE. UPON ARRIVAL THE OPS SPECIALIST NOTICED THAT RELIEVE VALVE NO. 17-4D WAS VENTING NATURAL GAS. CONSEQUENTLY, THE OPERATIONS SPECIALIST CLOSED THE BLOCK VALVE UNDER THE RELIEF VALVE THEREBY STOPPING THE RELEASE AT 10:52 LOCAL TIME. THIS CALCULATED TO BE 1,828 MCF AND WAS DETERMINED TO BE LESS THAN THE PHMSA 3,000 MCF AND NOT REPORTABLE AT THE TIME. ON JUNE 22, 2022, IT WAS DETERMINED THAT THE TOTAL RELEASE TIME DID NOT INCLUDE THE ACTUAL INITIAL NOTIFICATION WHEN GAS CONTROL RECEIVED THE NOISE COMPLAINT AND THE INITIAL CALCULATED VOLUME UTILIZED THE INCORRECT RELIEF VALVE ORIFICE SIZE. THEREFORE, THE TOTAL TIME OF THE RELEASE CHANGED FROM 8 MINUTES TO 26 MINUTES AND, THE TOTAL RELEASE VOLUME WITH THE REVISED ORIFICE SIZE EXCEEDED THE REPORTING THRESHOLD. THE NEW GAS LOSS VOLUME CHANGED FROM 1,828 MCF TO 10,814 MCF. THE EVENT WAS REPORTED TO THE NRC ON JUNE 22, 2022 AT 15:40 PM LOCAL TIME. THE INVESTIGATION INTO THE RELEASE REVEALED THAT THE RELIEF VALVE FAILED IN THE OPEN POSITION DUE TO DEBRIS AND FAILED SOFT GOODS INTERNAL TO THE PILOT VALVE, WHICH CONTROLS THE RELIEF VALVE. ONCE THE PILOT WAS CLEANED, SERVICED AND REBUILT THE VALVE AND PILOT VALVE WAS SUCCESSFULLY TESTED AND RETURNED TO SERVICE.