PUGET SOUND ENERGY

Incident Narrative

PUGET SOUND ENERGY (PSE) AND INFRASOURCE (IFS) WERE PERFORMING REPLACEMENT WORK ON A REGULATOR STATION FACILITY. THE FACILITY WAS ISOLATED FROM THE SURROUNDING SYSTEM BY CLOSING THE INLET AND OUTLET VALVES AND HAD BEEN BLOWN DOWN AND PURGED OUT OF SERVICE USING NITROGEN. THE IFS CREW WAS WORKING REBUILDING A STATION REGULATOR RUN BY ON WELDING A FLANGE ONTO AN OPEN PIPE RISER WHEN UNINTENTIONAL IGNITION OCCURRED. TWO CREW MEMBERS WERE TRANSPORTED TO THE HOSPITAL: AN IFS WELD HELPER WAS TREATED IN THE ER AND RELEASED, AND A PSE PRESSURE CONTROL TECHNICIAN WAS ADMITTED TO THE HOSPITAL AT 20:05 FOR BURN TREATMENT. OUR INVESTIGATION WAS INCONCLUSIVE, BUT OUR WORKING ASSUMPTION IS THAT ONE OF THE CLOSED VALVES BYPASSED A SMALL AMOUNT OF GAS. THE CONSTRUCTION PROCEDURE THAT WAS BEING FOLLOWED DURING THE PROJECT CONTAINED SEVERAL ISOLATION AND MONITORING STEPS: - THE VALVES ISOLATING THE WORK AREA FROM THE ACTIVE SYSTEM WERE SUBJECTED TO A ""SHUT IN TEST"" AND PASSED THE TEST. - THE PIPING IN THE WELD AREA HAD BEEN INERTED USING NITROGEN, BUT THE IGNITION OCCURRED SEVERAL HOURS AFTER INTERTING PROCESS HAD BEEN COMPLETED. - THE CREW WAS MONITORING FOR GAS READS IN THE INERTED PIPE RISERS AS PART OF THE WELDING PROCESS AND CONFIRMED 0% GAS READS. INVESTIGATION AFTER THE INCIDENT FOUND GAS READS ON THE INERTED SIDE OF THE CLOSED STATION OUTLET VALVE. THE VALVE WAS GREASED TO BRING THESE READS TO 0% GAS. AS PART OF THE FOLLOW UP FROM A SAFETY DEPARTMENT LED ROOT CAUSE ANALYSIS, PSE IS REVISING ENERGY CONTROL PROCEDURES TO ADDRESS THE POSSIBILITY THAT GAS MIGHT LEAK BY A CLOSED VALVE. PSE IS ALSO ADDRESSING MANAGEMENT OF CHANGE FOR WRITTEN CONSTRUCTION PROCEDURE UPDATES, SINCE LAST MINUTE CHANGES NEEDED TO BE MADE TO THE PROCEDURE DOCUMENT FOR THE REGULATOR STATION CONSTRUCTION PROJECT BASED ON PIPING CONDITIONS FOUND IN THE FIELD.