TEXAS EASTERN TRANSMISSION, LP (SPECTRA ENERGY PARTNERS, LP)

Incident Narrative

ORIGINAL REPORT: 48 HR NRC REPORT 1246924 AT APPROXIMATELY 6:30 AM EDT ON MAY 25, 2019, TEXAS EASTERN TRANSMISSION (TETLP) RECEIVED NOTIFICATION FROM A LAND OWNER ABOUT A RELEASE OF NATURAL GAS AT TETLP'S METER AND REGULATOR STATION (M&R 71144) IN BEDFORD COUNTY, PA. TETLP'S EMPLOYEE ARRIVED AT M&R 71144 AT APPROXIMATELY 7:00 AM EDT AND DISCOVERED A NATURAL GAS RELEASE THROUGH A RELIEF VALVE. THE EMPLOYEE STOPPED THE RELEASE BY CLOSING AN ISOLATION VALVE. THE RELIEF VALVE ACTIVATED BECAUSE THE CUSTOMER DEMAND HAD DROPPED TO ZERO FLOW (NOT UNUSUAL WITH WARM WEATHER) AND THE PRIMARY PRESSURE REGULATOR (SET AT 285 PSIG) SHUT OFF (AS INTENDED) THOUGH IT LEAKED A SMALL QUANTITY OF GAS THROUGH IT. THE SMALL LEAKAGE CAUSED THE PRESSURE TO BUILD UP UNTIL THE RELIEF VALVE ACTIVATED AT 300 PSIG. TETLP'S EMPLOYEE SUBSEQUENTLY INSPECTED THE RELIEF VALVE AND PRESSURE REGULATOR AND DETERMINED THAT THERE WERE NO MECHANICAL FAILURES (OTHER THAN THE SMALL LEAKAGE THROUGH THE REGULATOR WHEN THE CUSTOMER DEMAND WAS ZERO). THERE WAS NO OTHER IMPACT DUE TO THE RELEASE. THE PRESSURE REGULATOR SETTING AND RELIEF VALVE SETTINGS WERE ADJUSTED TO ACCOMMODATE FOR LOW DEMAND SUMMER CONDITIONS. TETLP REVIEWED THE SCADA DATA AT APPROXIMATELY 9:45 AM EDT ON MAY 25, 2019 AND DETERMINED THAT THE RELIEF VALVE BEGAN VENTING AT APPROXIMATELY 2 AM EDT ON MAY 25, 2019. TETLP WAS ABLE TO CALCULATE THE GAS LOSS BY CALCULATING THE RELIEF VALVE CAPACITY FLOW RATE AND OVER A 5-HOUR DURATION. TETLP SUBSEQUENTLY NOTIFIED THE NRC AT APPROXIMATELY 10:02 EDT.