TENNESSEE GAS PIPELINE COMPANY

Incident Narrative

APPROXIMATELY 14:55 (EASTERN), OPERATIONS STAFF WERE WORKING IN A ESD RELAY PANEL. AN INADVERTENT ESD SIGNAL WAS SENT TO BUILDING ""C"" RESULTING IN CLOSURE OF TWO VALVES. COMPRESSOR UNITS IN BUILDING ""B"" AND ""D"" WERE ON LINE. OVERPRESSURING BEGAN TO OCCUR IN A DISCHARGE HEADER; RELIEF VALVE 106-BD5 LIFTED THEN RESEATED. RELIEF VALVE 106-BD3 ALSO LIFTED AND RESEATED. HOWEVER RELIEF VALVE 106-BD3 LIFTED AGAIN BUT DID NOT RESEAT DUE TO DAMAGE CAUSED BY THE PASSING OF HIGH PRESSURE GAS. STATION EMPLOYEES OBSERVED THE EVENT AND ISOLATED THE GAS FLOW AS QUICKLY AS POSSIBLE. THE FOLLOWING INVESTIGATION FOUND A LOOSE WIRE, A DIODE JUMPER, HAD BECOME DISLODGED FROM THE RELAY IN THE PANEL CAUSING THE INADVERTENT ESD SIGNAL. RELIEF VALVE 106-BD3 WAS REPAIRED AS WELL AS THE LOOSE WIRE. APPROPRIATE CHECKS AND INSPECTIONS WERE MADE AND COMPRESSOR STATION RETURNED TO SERVICE. THE WORK AT THE RELAY PANEL INVOLVED BUILDING ""A"". WITH POST-EVENT INVESTIGATION AND FOLLOW-UP, THE RESPECTIVE WIRING HAS BEEN REVISED TO SEPARATE BUILDING ""A"" FROM IMPACTING OTHER BUILDINGS. ALSO, POST-EVENT INVESTIGATION FOUND FINAL GAS LOST VOLUME LESS THAN ORIGINALLY CALCULATED AND REPORTED TO NRC.