NATURAL GAS PIPELINE CO OF AMERICA (KMI)

Incident Narrative

"AT 6:50AM ON DECEMBER 26TH, AN OFF-SITE EMPLOYEE RECEIVED A CALLOUT FROM THE AUTOMATED SYSTEM FOR AN EQUIPMENT FAILURE ALARM. AT 7:02AM, WHILE THE EMPLOYEE WAS RESPONDING TO THE ALARM, HE RECEIVED A CALL FROM GAS CONTROL. GAS CONTROL INFORMED THE EMPLOYEE OF A PERCENT CHANGE ALARM ON THE #3-LINE SUCTION PRESSURE TRANSMITTER. SEPARATE OPERATOR RESOURCES ARRIVED AT THE STATION AND DISCOVERED THAT THE STATION WAS VENTING GAS THROUGH BOTH SUCTION BLOWDOWN VALVES. THE #3 SUCTION SIDE GATE VALVE WAS OPEN AND ALLOWED GAS TO VENT. AT 7:55AM, THE #3 SUCTION SIDE GATE VALVE WAS CLOSED MANUALLY BY THE EMPLOYEE AND THE STATION COMPLETED THE BLOW DOWN PROCESS. INVESTIGATION DETERMINED THAT THE ROBERTSHAW RELAY, WHICH KEEPS THE 1-INCH ESD BLOCK VALVE IN THE CLOSED POSITION, WAS FAULTY. THIS ALLOWED THE 1-INCH ESD BLOCK VALVE TO LEAK THROUGH THE VENT AND CAUSED THE VALVE TO PARTIALLY OPEN AND PRESSURE UP THE ESD SUPPLY GAS SYSTEM, THUS TRIGGERING A STATION ESD. ADDITIONALLY, MOISTURE HAD ACCUMULATED IN THE ESD SENSING LINES (NORMALLY DEPRESSURIZED) AND SHAFER TRIGGER VALVE THAT SENDS A CLOSE SIGNAL TO THE ESD SUCTION SIDE GATE VALVE. THE MOISTURE FROZE DURING THE COLD AMBIENT TEMPERATURES EXPERIENCED AT NGPL 305 ON THE MORNING OF 12/26/2023. THE PRESENCE OF ICE IN THE ESD SENSING LINES PREVENTED THE #3 SUCTION SIDE GATE VALVE FROM CLOSING AS DESIGNED. NGPL REPLACED THE ROBERTSHAW RELAY AND USED NITROGEN TO BLOW OUT ANY WATER IN THE ESD SYSTEM. THE ESD SYSTEM WAS PRESSURED UP AND SUCCESSFULLY CHECKED FOR LEAKS."