ENABLE GAS TRANSMISSION, LLC

Incident Narrative

OPERATIONS PERSONNEL ARRIVED AT THE WOODAL PLANT YARD ON APRIL 11TH AND DISCOVERED A RELIEF VALVE VENTING ON LINE AD-23. THE RELIEF WAS ISOLATED AND IT WAS DISCOVERED THE RELIEF WAS RELIEVING PREMATURELY 967 PSI. THE MAOP OF AD-23 IS 1000 PSI. THE NRC WAS NOTIFIED ON 4/11/2022 (#1333256) OF THE RELEASE AND A 48 HR. FOLLOW UP WAS PROVIDED ON 4/12/2022 (#1333381). THIS RELIEF VALVE HAS RELIEVED PREMATURELY PREVIOUSLY AND OPERATIONS ORDERED A REPLACEMENT VALVE IN APRIL OF 2022. LEAD TIME ON THE NEW VALVE WAS 18 WEEKS AT TIME OF ORDER AND HAS NOT YET BEEN RECEIVED. AFTER THIS RELEASE WAS SECURED, OPERATIONS NOTICIDED THE THE EXISTING VALVE WAS A DIAPHRAGM TYPE PILOT AND THOUGHT THAT MIGHT BE THE ISSUE CAUSING IT TO RELIEVE PREMATURELY. THE PILOT HAS SINCE BEEN UPGRADED FROM A DIAPHRAGM TYPE TO A PISTON TYPE. THE OPERATIONS GROUP LOCATED A PISTON PILOT THAT WAS NOT IN USE AND A SPARE PISTON PILOT OPERATOR HAS BEEN ORDERED TO KEEP ON THE SHELF (TENTATIVELY SCHEDULED FOR RECEIPT IN AUGUST 2022). A FULL REBUILD KIT FOR THE RELIEF VALVE HAS BEEN ORDERED AS WELL SHOULD IT BE NEEDED. A PROJECT IS BEING DEVELOPED TO POSSIBLY RELOCATE THE VALVE. LINE AD-23, ADM-14, AND LINE AD-WEST ARE ALL TIED TOGETHER AT THE WOODALL PLANT YARD. ALL LINES HAVE A 1000 PSI MAOP AND ARE ALL COMMON. OVER THE LAST COUPLE OF YEARS, AD-WEST HAS ROUTINELY OPERATED AT A HIGHER PRESSURE ANYWHERE FROM 925 TO 975 PSI. SINCE EACH RELEASE HAS BEEN PREMATURE, ENABLE THOUGHT REPLACING THE DIAPHRAGM PILOT (WHICH HAS A +/- 5% INITIATION) WITH A PISTON PILOT WOULD ALLOW AD-WEST TO OPERATE CLOSER TO MAOP. THE DIAPHRAGM WORKED WELL WHEN THE LINE WAS OPERATING AT A LOWER PRESSURE BUT COULD CONTINUE TO PREMATURELY RELIEVE +/- 50 PSI EARLY IF NOT CHANGED TO THE PISTON STYLE. 05.12.2022 SUPPLEMENTAL PART H NARRATIVE UPDATED.