KINDER MORGAN TEJAS PIPELINE

Incident Narrative

AT 4:40 AM ON APRIL 19TH, 2019 NATURAL GAS PIPELINE CO. OF AMERICA, LLC (NGPL) RECEIVED A CALL FROM FIRST RESPONDERS IN BANQUETE, TX REPORTING A LOUD NOISE. NGPL NOTIFIED KINDER MORGAN TEJAS PIPELINE, LLC (TEJAS) WHO SHUT DOWN THE BANQUETE COMPRESSOR STATION AT 5:18 AM. A TEJAS OPERATOR ARRIVED ON SITE AT 5:23 AM. AT 5:31 AM IT HAD BEEN DETERMINED THAT THE 4"" RELIEF VALVE CONNECTED TO TRAILSTONE UNIT 5010 HAD BEEN RELIEVING PRESSURE CAUSING THE LOUD NOISE. THE UNIT WHICH WAS RUNNING AT THE TIME OF THE EVENT WAS LOCKED OUT AND THE STATION WAS BROUGHT BACK ONLINE AT 6:45 AM. A UNIT DISCHARGE RELIEF VALVE WAS FOUND TO HAVE DRIFTED FROM ITS LAST KNOWN SET PRESSURE, OPENING PREMATURELY AT 846 PSIG RELEASING 8,802 MCF. THE INVESTIGATION FOUND THAT THE RELIEF VALVE'S DESIGNED SET POINT IS 1050 PSIG HOWEVER, THE INVESTIGATION ALSO FOUND THAT THE RELIEF VALVE WAS LAST SET AT 970 PSIG. IT IS BELIEVED THAT THE CAUSE FOR THE RELIEF VALVE DRIFT WAS DUE TO VIBRATION AND PRESSURE PULSATIONS FROM THE UNIT. ADDITIONAL CONTRIBUTING FACTORS TO THE AMOUNT OF UNINTENTIONAL RELEASED GAS WAS THAT THE RELIEF VALVE'S VENT LINE CONNECTING PIPE NIPPLE FOR THE PRESSURE SWITCH WAS FOUND TO HAVE BEEN BROKEN AT THE CONNECTING THREADS TO THE PRESSURE SWITCH. BY VISUAL EXAMINATION THE PIPE NIPPLE WAS DETERMINED NOT TO MEET TEJAS SCHEDULE 160 REQUIREMENTS. POST-INCIDENT IT WAS DISCOVERED THAT THE LADDER LOGIC ASSOCIATED WITH THE PRESSURE SWITCH HAD NOT BEEN ENABLED. HAD THE LADDER LOGIC BEEN ENABLED, WITH THE ACTIVATION OF THE PRESSURE SWITCH, IT WOULD HAVE STOPPED THE UNIT THEREFORE REDUCING THE AMOUNT OF UNINTENTIONAL RELEASED GAS. UPON RESTARTING THE UNIT AFTER THE EVENT, THE TECHNICIAN NOTICED THERE WAS BACKFLOW INTO THE UNIT COMING FROM THE DISCHARGE PIPING DOWNSTREAM OF THE CHECK VALVE. FURTHER INVESTIGATION OF THE CHECK VALVE DETERMINED THAT THE CHECK VALVE'S FLAPPER ON THE DISCHARGE PIPELINE FAILED DURING THIS EVENT. HOWEVER, IT IS NOT BELIEVED THAT THIS FAILURE WAS A CONTRIBUTING FACTOR TO THE AMOUNT OF GAS RELEASED RATHER IT WAS A RESULT OF THE DISCHARGE PULSATING EVENTS ASSOCIATED WITH THE CONTINUED COMPRESSOR OPERATIONS AND THE PRESSURE FLUCTUATIONS ASSOCIATED WITH THE ON/OFF ACTIVATION OF THE DISCHARGE RELIEF VALVE. THE 48-HR NRC INCIDENT REPORT NUMBER IS 1243256.