ENOGEX LLC

Incident Narrative

AT 06:00 ON 2/10/11 PURCHASED POWER WAS LOST AT THE ENOGEX CANUTE COMPRESSOR STATION, DUE TO THE POWER COMPANY'S TRANSFORMER FAILURE. BATTERY BACKUP TOOK OVER AND LASTED FOR APROXIMATELY 30 MINUTES. AT 06:29 AFTER THE BATTERY BACK UP RAN DOWN THE COMPRESSOR UNITS SHUT DOWN AND THE STATION ESD SYSTEM WAS AUTOMATICALLY ACTIVATED. AT THIS TIME GAS CONTROL RECEIVED AN ALARM THAT THE UNITS SHUT DOWN. GAS CONTROL NOTIFIED THE COMPRESSOR FOREMAN AND HE CONTACTED A COMPRESSOR TECH TO RESPOND TO THE ALARM. THE COMPRESSOR TECH ARRIVED ON LOCATION AT APPROXIMATELY 07:35. THE COMPRESSOR TECH FOUND ALL COMPRESSOR UNITS SHUT DOWN AND THE ESD SYSTEM HAD ACTIVATED. THE COMPRESSOR TECH CONFIRMED NATURAL GAS WAS VENTING TO ATMOSPHERE THROUGH A 2 INCH ESD VENT VALVE FOR UNIT 413 AND THAT THE SUCTION ESD VALVE FOR THE UNIT WAS NOT FULLY CLOSED. AFTER FURTHER INSPECTION IT WAS DISCOVERED THAT THE SOLENOID VALVE CONNECTED TO THE ESD VALVE ACTUATOR HAD AN INTERNAL ICE BLOCKAGE THAT PREVENTED PROPER OPERATION OF THE ACTUATED VALVE. THIS RESULTED IN A RELEASE OF NATURAL GAS THROUGH THE 2 INCH VENT VALVE AT A PRESSURE OF 835 PSIG FOR APPROXIMATELY 2.5 HOURS. PERSONNEL REMOVED THE ACTUATOR ON THE VENT VALVE AND MANUALLY CLOSED THE VALVE TO STOP THE GAS RELEASE. IN ADDITION, THE SOLENOID VALVE WAS THAWED TO CLOSE THE SUCTION ESD VALVE. IN ORDER TO PREVENT RECURRENCE, NEW BATTERIES WERE INSTALLED FOR THE BACK UP SYSTEM. IN ADDITION, THE INSTRUMENT GAS SUPPLY TO THE ESD SYSTEM WILL BE CONVERTED OVER TO A DRIER INSTRUMENT AIR SYSTEM. UPDATE MARCH 5, 2013: COMPLETED SECTION E.5.F.