TENNESSEE GAS PIPELINE COMPANY

Incident Narrative

ON OCTOBER 5, 2023 AT 06:58 (EST), STATION 267 IN HOPKINTON, MA EXPERIENCED AN ESD EVENT. THE INITIAL NOTIFICATION WAS RECEIVED VIA SCADA ALARMS. GAS CONTROL PERSONNEL NOTIFIED TGP OPERATIONS PERSONNEL WHO WERE IN ROUTE TO THE STATION FOR DAILY ACTIVITIES. TGP OPERATIONS PERSONNEL ARRIVED ONSITE AT 07:11 (EST). THE HOPKINTON FIRE DEPARTMENT HAD BEEN NOTIFIED BY A THIRD-PARTY AND ARRIVED ONSITE AT 07:18 (EST). ONCE TGP OPERATIONS PERSONNEL ARRIVED ONSITE, THEY OBSERVED THAT STATION 267 WAS VENTING, BUT THE COMPRESSOR STATION WAS NOT FULLY ISOLATED FROM THE MAINLINE. DURING A STATION WALKTHROUGH BY OPERATIONS PERSONNEL, IT WAS DISCOVERED THAT THE COMPRESSOR STATION SIDE GATE VALVES WERE PARTIALLY OPEN. THUS GAS FROM THE MAINLINE WAS VENTING THROUGH THE STATION. AT 7:38 (EST), TGP OPERATIONS PERSONNEL CLOSED THE COMPRESSOR STATION BLOWOFF VALVES TO STOP VENTING OF THE GAS. AT 3:00 (EST), STATION 267 WAS CONFIRMED TO BE ISOLATED FROM THE MAINLINE. SINCE THIS EVENT, STATION 267 HAS REMAINED ISOLATED. FOLLOWING THE INTERNAL INVESTIGATION, IT WAS DETERMINED THAT A POWER FAULT IN THE AREA RESULTED IN THE FAILURE OF THE STATION PLC. THE PLC FAILURE ACTIVATED THE BUILDING PROTECTION SYSTEM, TRIGGERING THE ESD. DUE TO THE ESD COMMAND, THE COMPRESSOR STATION VENT VALVES WERE OPENED TO BLOW DOWN THE UNITS. HOWEVER, THE COMPRESSOR SIDE GATE VALVES FAILED TO PROPERLY CLOSE AND ISOLATE THE STATION. THE GAS LOSS DUE TO THIS EVENT WAS CALCULATED TO BE 8664 MCF. IN ORDER TO PREVENT REOCCURRENCE, NEW PLCS HAVE BEEN ORDERED AND WILL BE INSTALLED. ADDITIONALLY, ALL OF THE COMPRESSOR STATION SIDE GATE VALVES HAVE BEEN EVALUATED TO ENSURE CORRECT FUNCTIONALITY. AS AN ADDED PRECAUTION, OPERATIONS HAS DEVELOPED A PROCEDURE FOR ISOLATING THE STATION FROM THE MAINLINE DURING EXTENDED PERIODS WHEN THE STATION IS NOT IN DEMAND. THE ACTION ITEMS ABOVE ARE INTENDED TO REDUCE THE POTENTIAL FOR REOCCURRENCE OF THIS EVENT.