DTE GAS COMPANY

Incident Narrative

AT APPROXIMATELY 14:05 A FLAME SENSOR NEAR COMPRESSOR UNIT 109 IN PLANT 1 ACTIVATED THE EMERGANCY SHUTDOWN (ESD) SYSTEM FOR PLANT 1. FOUR RELIEF VALVE OPERATORS PROPERLY ACTUATED TO OPEN, RELEASING NATURAL GAS TO THE ATMOSPHERE IN ACCORDANCE WITH THE ESD SYSTEM DESIGN. THE ESD ALSO TRIGGERED FOUR BLOCK VALVE OPERATORS INTENDED TO ISOLATE PLANT 1 FROM THE INLET (SUCTION) AND OUTLET (DISCHARGE) PIPELINES; HOWEVER, ONLY ONE OF THE FOUR BLOCK VALVES ACTUALLY CLOSED. LOCAL OPERATING PERSONNEL DETERMINED THAT EXTREME WEATHER OVER THE PAST DAYS (TEMPERATURES AS LOW AS -15 DEGREES F, WINDY AND SNOW CONDITIONS) MAY HAVE PREVENTED THE HYDRAULIC ACTUATING SYSTEMS FOR THE REMAINING THREE BLOCK VALVE OPERATORS FROM CLOSING THOSE THREE VALVES. LOCAL OPERATING PERSONNEL MANUALLY OPERATED THE REMAINING THREE BLOCK VALVES, CLOSING THE LAST ONE AT APPROXIMATELY 14:59. ONCE THE LAST OF THE THREE REMAINING BLOCK VALVES WERE CLOSED, THE PIPING TO PLANT 1 CONTINUED TO BLOW DOWN TO ATMOSPHERIC PRESSURE IN UNDER A MINUTE. AT NO TIME WAS MAOP OF THE COMPRESSOR STATION PIPING EXCEEDED. INVESTIGATION REVEALED THERE WAS NO FIRE OR IGNITION INSIDE THE BUILDING AT PLANT 1. INVESTIGATION CONTINUES INTO WHETHER THE FLAME SENSOR MAY HAVE BEEN FAULTY AND NEEDS TO BE REPLACED.