TENNESSEE GAS PIPELINE COMPANY

Incident Narrative

ON AUGUST 30, TENNESSEE GAS PIPELINE (TGP), AN ON-DUTY STATION TECHNICIAN WAS PERFORMING HIS INSPECTION ROUNDS AT COMPRESSOR STATION 313 AND DISCOVERED AN AUTOMATED EMERGENCY SHUT DOWN (ESD) FUEL GAS BLOCK VALVE PARTIALLY OPEN ALLOWING NATURAL GAS TO VENT TO ATMOSPHERE. UPON DISCOVERY OF THE UNDESIRABLE SITUATION, THE ON-DUTY STATION TECHNICIAN MANUALLY CLOSED THE AUTOMATED ESD FUEL GAS BLOCK VALVE THEREBY IMMEDIATELY TERMINATING THE NATURAL GAS RELEASE. OPERATIONS INITIATED THE EMERGENCY RESPONSE LINE (ERL) PER O&M PROCEDURES AND THE INCIDENT WAS REPORTED. THE TGP INVESTIGATION CONCLUDED THE GAS RELEASE BEGAN AFTER AN ESD EVENT DEMONSTRATION REQUESTED BY PHMSA ON AUGUST 18, 2021. AFTER THE ESD DEMONSTRATION EVENT, THE AUTOMATED VALVE OPERATOR FAILED TO FULLY CLOSE THE AUTOMATED ESD FUEL BLOCK VALVE. THE ESD SYSTEM VENT VALVE WAS IN THE CORRECT OPEN POSITION THUS ALLOWING THE NATURAL GAS TO RELEASE TO ATMOSPHERE. THE INVESTIGATION FURTHER CONCLUDED THE STATION TECHNICIAN PERFORMING THE DEMONSTRATION FAILED FOLLOW THE SITE-SPECIFIC PROCEDURE AND DID NOT VISUALLY CHECK THE FINAL POSITIONS OF THE AUTOMATED ESD FUEL BLOCK VALVE AND THE ESD VENT VALVE. TGP REVOKED THE ASSOCIATED ESD TESTING OPERATOR QUALIFICATION (OQ) FOR THE STATION TECHNICIAN INVOLVED WITH THE ESD TEST DEMONSTRATION. ADDITIONALLY, SUBSEQUENT INVESTIGATION TESTING FOUND THE AUTOMATED VALVE OPERATOR APPLICABLE TO THE ESD FUEL BLOCK VALVE TO BE UNRELIABLE. A REPLACEMENT VALVE OPERATOR HAS BEEN ORDERED FOR THE AUTOMATED ESD FUEL BLOCK VALVE.