SOUTHERN NATURAL GAS CO

Incident Narrative

AT 3:17 AM SOUTHERN NATURAL GAS COMPANY, L.L.C. (SNG) GAS CONTROL RECEIVED A PHONE CALL FROM THE PUBLIC REGARDING A LOUD NOISE COMING FROM A PIPELINE FACILITY. A SNG TECHNICIAN WAS CALLED OUT TO THE SITE AND ARRIVED AT 3:45 AM. UPON ARRIVAL THE TECHNICIAN MET WITH EMERGENCY RESPONDER PERSONNEL WHO PROCEEDED TO BLOCK THE ACCESS ROAD TO THE COMPRESSOR STATION. THE TECHNICIAN ATTEMPTED TO CLOSE THE EMERGENCY BLOWDOWN VALVE AND WAS UNABLE TO, SO THE DECISION WAS MADE TO ESD THE STATION, THUS ENDING THE GAS RELEASE. AN ERL (EMERGENCY RESPONSE LINE) CONFERENCE CALL WAS HELD AT 4:10 AM ABOUT THE EVENT. ON THE CALL IT WAS FORECASTED THAT THE GAS LOSS FROM THE EVENT WOULD EXCEED THE REPORTABLE THRESHOLD OF 3,000 MCF. AT THIS TIME (4:10 AM) SNG HAD CONFIRMED DISCOVERY OF THE INCIDENT. THE PILOT IN THE EMERGENCY BLOWDOWN VALVE WAS REPLACED. AFTER INVESTIGATING, IT WAS DETERMINED THAT THE PILOT ACTUATOR OF THE EMERGENCY BLOWDOWN VALVE HAD A LEAKING SEAL ON THE POWER GAS SIDE. IT IS BELIEVED THAT THE ESCAPING GAS FROM THE SEAL MADE ITS WAY TO THE VENT WHERE IT FROZE OVER THE EXHAUST PORT, PREVENTING THE LEAKING GAS FROM REACHING ATMOSPHERE. THE PRESSURE FROM THE LEAKING GAS CONTINUED TO BUILD, AND UPON REACHING 150 PSI THE VALVE OPERATOR ACTIVATED TO ITS ""SAFE STATE"" AS IT IS DESIGNED TO DO, AND IN THIS CONFIGURATION THE SAFE STATE HAS THE VALVE IN THE OPEN POSITION. THE VALVE OPERATOR'S SAFE STATE CONFIGURATION RESULTED IN THE EMERGENCY BLOWDOWN VALVE OPENING WITHOUT SNG'S COMMAND. BEFORE THE EVENT, SNG HAD IDENTIFIED THE VALVE OPERATOR AS LEAKING AND MADE PLANS TO ADDRESS THE LEAK, BUT DUE TO NOT BEING AWARE OF THIS OPERATOR'S FAIL SAFE MODE AN INCORRECT ASSESSMENT OF THE TIMEFRAME FOR REPAIR WAS MADE. AT THOMASTON COMPRESSOR STATION, SNG HAS MODIFIED ITS LEAK SURVEY WORK ORDERS ON ESD VENT VALVES WITH THIS TYPE OF OPERATOR SO THAT THE TECHNICIANS WHO COMPLETE THE WORK ORDER ARE INSTRUCTED TO PROMPTLY REPAIR ANY FOUND LEAK ON THE OPERATOR.