TENNESSEE GAS PIPELINE COMPANY — Gas transmission and gathering — incident on 2018-11-28

Gas transmission and gathering incident in Not Within a Municipality, HARDEMAN COUNTY County, TN. Reported cause: NATURAL FORCE DAMAGE. Reported consequences: 0 fatalities, 0 injuries, 7501 NATURAL GAS released, $1,800 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: 20180127.

Operator ID: 19160.

Reported incident date: 11/28/2018 4:35.

Location detail: MLV 71-1

Cause detail: TEMPERATURE

Cause detail: AT APPROXIMATELY 06:00 HOURS, 11/28/2018, A TGP EMPLOYEE ARRIVED AT STATION 71 AND DISCOVERED NATURAL GAS BLOWING FROM THE 2-INCH UNIT VENT VALVE ON COMPRESSOR UNIT 1B. THE EMPLOYEE IMMEDIATELY CONTACTED THE STATION SUPERVISOR FOR EVENT NOTIFICATION. THE STATION SUPERVISOR IMMEDIATELY DISPATCHED ADDITIONAL EMPLOYEES TO ASSIST. THE STATION E&C TECHNICIAN ARRIVED AT STATION 71 AT 6:20 HOURS AND CONFIRMED NATURAL GAS BLOWING FROM THE 2-INCH UNIT VENT VALVE AND DISCOVERED THE UNIT DISCHARGE VALVE WAS OPEN. AT 6:25 HOURS, THE MANUAL LOCKING VALVE BENEATH THE 2-INCH UNIT VENT VALVE WAS CLOSED THEREBY TERMINATING THE NATURAL GAS RELEASE. THE 2-INCH UNIT VENT VALVE WAS ALSO CLOSED. THE UNIT HAD PREVIOUSLY BEEN BLOWN DOWN FROM AN EARLIER EMERGENCY SHUTDOWN (ESD) TEST AND WAS LEFT WITH THE 2-INCH VENT VALVE IN THE NORMAL OPEN POSITION. AS PART OF POST INCIDENT INVESTIGATION, PRESSURE TRENDING INFORMATION WAS ANALYZED AND IT WAS DETERMINED THE DISCHARGE VALVE OPENED AT 3:25 HOURS AND REPORTABLE VOLUME WAS MET AT 04:35 HOURS. INVESTIGATION ALSO IDENTIFIED ICE HAD FORMED IN THE CONTROL SYSTEM OF THE UNIT 1B DISCHARGE VALVE, IMPAIRING ITS OPERATION, ALLOWING THE DISCHARGE VALVE TO OPEN PREMATURELY THEREFORE ALLOWING NATURAL GAS TO VENT THROUGH THE OPEN 2-INCH UNIT VENT VALVE TO ATMOSPHERE. POST EVENT REPAIRS INCLUDED THE CONTROL SYSTEM OF THE UNIT DISCHARGE VALVE WAS BLOWN CLEAN, FREE OF MOISTURE, AND THE CONTROL SYSTEM FILTER WAS REPLACED. PRIOR TO RETURN TO SERVICE, THE 2-INCH UNIT VENT VALVE WAS CONFIRMED RETURNED TO THE OPEN POSITION, ALSO THE MANUAL LOCKING VALVE BENEATH THE 2-INCH UNIT VENT VALVE WAS CONFIRMED RETURNED TO THE OPEN POSITION. THE UNIT SUCTION AND THE UNIT DISCHARGE VALVES WERE CONFIRMED PROPERLY CLOSED. COMPRESSOR UNIT 1B WAS CONFIRMED SAFE AND READY TO RETURN TO SERVICE AS NEEDED ON 11/28/2018. SINCE 11/28/2018, OPERATIONS HAS REVISED THE WINTERIZATION PLAN FOR STATION 71 TO INCLUDE INSPECTION OF VALVE CONTROL SYSTEMS TO DISCOVER CONDENSATE ISSUES AND ELIMINATE THE ISSUES BEFORE FREEZING CONDITIONS BEGIN. PLEASE NOTE THE FOLLOWING REQUESTED INFORMATION: THE ORIGINAL NRC REPORT NUMBER IS 1231460. THE UPDATED INFORMATION NRC REPORT NUMBER IS 1231506. THE REQUIRED PHMSA 48-HOUR NRC REPORT NUMBER IS 1231637.

PHMSA trend classification: not significant, not serious.

PHMSA standardized cause: NATURAL FORCE DAMAGE — TEMPERATURE.

PHMSA indexed costs: $34,380 reported total cost, $30,827.128 in 1984 dollars, $39,502.67 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.