COLUMBIA GULF TRANSMISSION, LLC

Incident Narrative

ON SEPTEMBER 12, 2020, AN ALARM WAS ACKNOWLEDGED BY THE US NATURAL GAS CONTROL, EAST TEAM, SUBJECT TO A POSSIBLE ALARM AT DELHI COMPRESSOR STATION (CS) UNIT 811. COLUMBIA GULF TRANSMISSION, LLC (COLUMBIA) OPERATES AND MAINTAINS DELHI CS WHICH IS CLASSIFIED AS A TRANSMISSION CS, IS LOCATED IN RICHLAND PARISH, LOUISIANA AND NEAR THE CITY OF DELHI. AFTER RECEIVING THE NOTIFICATION FROM COLUMBIA MONITORING CENTER, CS PERSONNEL RESPONDED TO THIS POSSIBLE ALARM AT DELHI CS AND ADDRESSED THE UNINTENDED RELEASE OF NATURAL GAS (MATERIAL) THAT WAS VENTING INTO ATMOSPHERE FROM BLOW DOWN DISCHARGE STACK 8SH-1BD. THE CS PERSONNEL INSPECTED AND SECURED THE AREA TO ENSURE THAT IT WAS SAFE TO OPERATE DISCHARGE VALVES BEFORE MANUALLY CLOSING THEM. INVESTIGATION INTO THE INCIDENT IDENTIFIED THE PROBABLE CAUSE THAT LED TO THIS UNINTENDED RELEASE WAS DUE TO THE OPEN COMMAND SOLENOID VALVE COIL (8SH-1BD) FAILING AS DETERMINED BY AN UNUSUALLY HIGH RESISTANCE MEASURED AT THE COIL. THIS SOLENOID VALVE IS A FAIL OPEN SOLENOID THAT REQUIRES VOLTAGE TO THE COIL TO KEEP THE VALVE IN THE CLOSED POSITION. ONCE THE COIL FAILED THE VALVE (8SH-1BD) BEGAN TO OPEN UNTIL THE CLOSED LIMITS WERE BROKEN. ONCE THE LIMITS WERE BROKEN THE CLOSE SOLENOID WHICH IS A FAIL CLOSED SOLENOID ENERGIZED AND ATTEMPTED TO CLOSE THE VALVE UNTIL THE CLOSE LIMIT SWITCHES WERE MADE. THE SOLENOID VALVE WAS REBUILT BY REPLACING ARMATURE, SPRING, ORING, AND COIL. THE LIMIT SWITCH CAMS WERE ADJUSTED AND TIGHTENED TO ENSURE THIS ISSUE DOESN'T RE-OCCUR. ALL ALARMS WERE CLEARED AT THE PLC CONTROL PANEL, REQUIRED FUNCTIONAL TESTS WERE CONDUCTED WITH NO NEW ERRORS GENERATED (TO ENSURE NORMAL OPERATION OF THE UNIT), THEN THE UNIT WAS RETURNED BACK TO SERVICE. ROUTINE SAFETY CHECKS WERE CONDUCTED WHERE THE UNIT WAS MONITORED FOR A WHILE, VERIFIED THAT ALL SYSTEMS ARE RUNNING IN NORMAL MODE WITH NO NEW ERRORS WERE GENERATED THEREAFTER. A CALCULATED VOLUME OF UNINTENDED RELEASED MATERIAL WAS 5,695.60 MCF INTO ATMOSPHERE WHERE THE RELEASED MATERIAL DID NEITHER IGNITE NOR CAUSE ANY DAMAGE TO ANY OF THE CS DEVICES.