TENNESSEE GAS PIPELINE COMPANY — Gas transmission and gathering — incident on 2018-09-06

Gas transmission and gathering incident in Not Within a Municipality, POWELL County, KY. Reported cause: EQUIPMENT FAILURE. Reported consequences: 0 fatalities, 0 injuries, 7533 NATURAL GAS released, $17,000 reported property damage. Operator-reported incident data submitted to PHMSA, generally within 30 days. Records may be supplemented or corrected and do not represent final agency causal findings.

Report number: 20180098.

Operator ID: 19160.

Reported incident date: 9/6/2018 15:03.

Location detail: 12+76

Cause detail: MALFUNCTION OF CONTROL/RELIEF EQUIPMENT

Cause detail: 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.

PHMSA trend classification: not significant, not serious.

PHMSA standardized cause: EQUIPMENT FAILURE — MALFUNCTION OF CONTROL/RELIEF EQUIPMENT.

PHMSA indexed costs: $41,245 reported total cost, $29,529.329 in 1984 dollars, $47,878 in current-year dollars.

PHMSA trend flags, standardized causes, and indexed costs are analytical fields added to operator-reported incident data. They do not represent final agency causal findings.