ENABLE GAS TRANSMISSION, LLC

Incident Narrative

ON JULY 27, 2017 AT 08:53, ENABLE GAS TRANSMISSIONS SYSTEM CONTROL RECEIVED A CALL FROM THE GENERAL PUBLIC REPORTING GAS VENTING AT THE RED MOON COMPRESSOR STATION IN MCCLURE, OKLAHOMA. AN ENABLE O&M TECHNICIAN ARRIVED AT THE RED MOON COMPRESSOR STATION AT 10:01 AND FOUND THE THERMAL RELIEF (3/4 MERCER VALVE 9100 SERIES THREADED WITH A D ORIFICE) ON THE KING TOOL SUCTION FILTER SEPARATOR WAS VENTING. THE COMPRESSORS AT RED MOON ARE NOT IN ACTIVE SERVICE. THE O&M TECHNICIAN INSTALLED A GAUGE TO CHECK THE PRESSURE AT THE RELIEF, AND FOUND IT TO BE 911 PSIG. THE MAOP FOR THE RED MOON COMPRESSOR STATION IS 1000 PSIG. THE THERMAL RELIEF IS SET AT 1000 PSIG. AT 10:05 THE O&M TECHNICIAN SHUT IN THE BLOCK VALVE BELOW THE RELIEF AND OPENED IT BACK UP TO SEAT THE RELIEF VALVE. AT THIS POINT, THE RELIEF VALVE SEATED OFF AND APPEARED TO BE WORKING NORMALLY. THE FILTER SEPARATOR IS NOT UNDER SCADA CONTROL. AT 10:12, SYSTEM CONTROL WAS CONTACTED TO REPORT FINDINGS AND THAT GAS WAS NO LONGER VENTING. SYSTEM CONTROL NOTIFIED THE ENABLE ON-CALL TEAM AND THE TEAM DECIDED THAT FURTHER INVESTIGATION WAS NECESSARY BEFORE CONFIRMING THE RELEASE WAS REPORTABLE. OPERATIONS AND ENGINEERING REVIEWED THE AVAILABLE INFORMATION AND CONFIRMED THE TIMING OF THE EVENT AND ESTIMATED THE GAS LOSS TOTAL ON JULY 27TH AT 14:02. A CALL WAS PLACED TO THE NRC AT 14:22 ON THE 27TH (NRC #1185443) AND A FOLLOW-UP WAS PROVIDED ON THE 28TH (NRC # 1185526) AT 10:48. AFTER CONFIRMING WITH SYSTEM CONTROL THE LEAK HAD STOPPED, THE O&M TECH TESTED THE RELIEF VALVE AND FOUND IT TO START SEEPING AT AROUND 980 PSIG. THE RELIEF VALVE WAS INSTALLED IN 2001, AND HAS BEEN INSPECTED EVERY YEAR WITH THE STATION RELIEF VALVES. A DECISION WAS MADE TO REPLACE THE VALVE. A REPLACEMENT WAS ORDERED ON JULY 27TH AND INSTALLED ON AUGUST 1ST. UPON INSPECTION, THE MALFUNCTIONING RELIEF VALVE DID NOT SHOW SIGNS OF INTERNAL FAILURE. IT WAS DETERMINED THE VALVE PREMATURELY LIFTED AND CONTINUED TO MALFUNCTION UNTIL THE O&M TECH CORRECTED THE PROBLEM. USING SCADA TRENDS, THE START OF THE RELEASE STARTED AROUND 965 PSIG ON JULY 26 AT 05:30 AND DID NOT CEASE UNTIL THE O&M TECHNICIAN CLOSED THE BLOCK VALVE ON JULY 27TH 10:05. THE TOTAL RELEASE TIME WAS ESTIMATED TO BE 28 1/2 HOURS RESULTING IN A GAS LOSS ESTIMATE OF 4,455 MCF.