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Incident Narrative

AT 10:03 AM AN I&E TECHNICIAN WAS WORKING INSIDE THE COMPRESSOR STATION OFFICE/MCC WHEN HE OVERHEARD GAS BLOWING OUTSIDE OF THE BUILDING. THE TECHNICIAN WENT OUTSIDE TO DISCOVER AN ESD SYSTEM VENT VALVE, ESV-303, 100% OPEN. THE TECHNICIAN THEN VERIFIED THERE WAS NOT AN ACTIVE ESD CONDITION ON THE STATION CONTROL COMPUTER. THE TECHNICIAN THEN PHONED A STATION OPERATOR TO ASSIST. THE STATION OPERATOR ARRIVED AT APPROXIMATELY 10:20 AM AND CLOSED A 12 INCH VALVE TO ISOLATE THE STATION FROM L-25. THE GAS RELEASE THROUGH ESV-303 IMMEDIATELY BEGAN TO DECREASE. AS THE NOISE GENERATED BY THE VENTING GAS SUBSIDED, THE OPERATOR THEN HEARD GAS BLOWING FROM A SECOND VENT VALVE, ESV-193, WITHIN THE COMPRESSOR YARD. THE OPERATOR THEN CLOSED A 16 INCH VALVE TO ISOLATE THE STATION FROM L-127. WITH THE STATION COMPLETELY ISOLATED FROM ALL CONNECTING PIPELINES, THE STATION PIPING QUICKLY VENTED TO ATMOSPHERE AND WAS FULLY DEPRESSURED AT 10:26 AM. THE I&E TECHNICIAN RETURNED TO THE CONTROL COMPUTER TO FIND AN ACTIVE ESD ALARM AND A UNIT 1056 COMPRESSOR SHUTDOWN ALARM HAD OCCURRED WHILE HE WAS OUTSIDE OF THE OFFICE. AN INVESTIGATION WAS CONDUCTED FOLLOWING THIS INCIDENT. THE INVESTIGATION CONCLUDED THAT THE INADVERTENT GAS RELEASE WAS CAUSED BY THE UNPLANNED OPENING OF TWO ACTUATED EMERGENCY SHUTDOWN VENT VALVES DUE TO INADEQUATE PILOT GAS PRESSURE. AN INSPECTION OF PILOT GAS SYSTEM TO DETERMINE THE PRESENCE OF FOREIGN MATTER SUCH AS PIPE SCALE, PIPELINE CONTAMINANTS, ETC. WILL BE PERFORMED. IN ADDITION, THE CONTINUED USE OF THE VALVE OPERATORS CURRENTLY INSTALLED ON THE EMERGENCY VENT VALVES WILL BE EVALUATED. UPDATE JULY 30, 2010: AN INSPECTION OF THE PILOT GAS SYSTEM REVEALED THAT NO FOREIGN MATTER WAS PRESENT IN THE PILOT GAS FILTRATION ASSEMBLY OR THE PILOT GAS REGULATORS. THE REGULATORS WERE REPLACED WITH NEW LIKE KIND. FINANCES HAVE BEEN APPROPRIATED FOR THE REPLACEMENT OF ALL EXISTING ESD VENT VALVE ACTUATORS. MATERIALS HAVE BEEN ORDERED AND INSTALLATION HAS BEGUN. UPDATE MAY 26, 2011: REPLACEMENT OF ESD VENT VALE ACTUATORS IS COMPLETE. UPDATE MARCH 5, 2013: COMPLETED SECTION E.5.F.