TENNESSEE GAS PIPELINE COMPANY — Gas transmission and gathering — incident on 2018-08-11

Gas transmission and gathering incident in Not Within a Municipality, JEFFERSON DAVIS County, LA. Reported cause: EQUIPMENT FAILURE. Reported consequences: 0 fatalities, 0 injuries, 3788 NATURAL GAS released, $2,000 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: 20180090.

Operator ID: 19160.

Reported incident date: 8/11/2018 9:03.

Location detail: MP 0; 0+00

Cause detail: COMPRESSOR OR COMPRESSOR-RELATED EQUIPMENT

Cause detail: IN THE TGP STATION 823 A-1 COMPRESSOR BUILDING, A GAS DETECTOR UNIT PROVIDE ALARM AT 20% LFL. THE ON DUTY OPERATOR SAFELY ENTERED THE BULDING TO STOP UNIT #4A BUT THE GAS DETECTOR UNIT SENSED 40% LFL AND INITIATED A COMPLETE STATION ESD. THE UNIT #4A, #2 CYLINDER HEAD END UNLOADER VALVE STEM HAD A PACKING LEAK OF APPROXIMATELY 5 MCF. DURING THE STATION ESD PROCESS WHICH STOPPED THE UNIT, THE PIPING SYSTEM DID NOT FULLY ISOLATE AS VALVE 823-AD1 DID NOT COMPLETELY CLOSE. OPERATION STAFF DETERMINED IT WAS SAFE TO CLOSE VALVE 823-AD1 THEREFORE TERMINATING THE RELEASE OF NATURAL GAS TO ATMOSPHERE. NOTIFICATIONS WERE MADE TO THE NRC AND TO THE LOUISIANA STATE POLICE AS REQUIRED. INVESTIGATION FOUND THE CYLINDER HEAD END UNLOADER POCKET PISTON SET SCREW HAD BACKED OUT ALLOWING A NUT TO LOOSEN; PULSATION CAUSED THE POCKET PISTON TO DISENGAGE; THE MISSING PISTON ALLOWED THE VALVE STEM TO OVER TRAVEL ALLOWING GAS TO VENT AROUND THE GLAND AND OUT TO ATMOSHPERE THROUGH AN UNLOADER WEEP HOLE. VALVE 823-AD1, SLIGHTLY OFF CLOSE LIMITS, ALLOWED ADDITIONAL VENTING OF NATURAL GAS BEFORE OPERATION STAFF SAFELY CLOSED THE VALVE. THE VALVE SET LIMITS HAVE BEEN RESET AND THE VALVE ASSEMBLY INPSECTED. THE HEAD END UNLOADER HAS BEEN REPAIRED. INSPECTION OF OTHER HEAD END UNLOADER COMPONENTS FOUND TWO OTHER UNITS WITH LOOSE SET SCREWS; THESE UNITS HAVE ALSO BEEN REPAIRED.

PHMSA trend classification: not significant, not serious.

PHMSA standardized cause: EQUIPMENT FAILURE — PUMP/COMPRESSOR OR PUMP/COMPRESSOR-RELATED EQUIPMENT.

PHMSA indexed costs: $15,830 reported total cost, $12,501.566 in 1984 dollars, $18,299.382 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.