NORTHWEST PIPELINE LLC

Incident Narrative

ON FEBRUARY 24TH, 2022 THERE WAS A WATER MAIN RUPTURE INSIDE THE CONTROLS ROOM AT NORTHWEST PIPELINE RANGELY COMPRESSOR STATION. EMERGENCY CONTROL DEVICES WERE IMPACTED AND EXPOSED TO WATER AS A RESULT OF THE LEAK, CAUSING OPERATIONS TO MAKE THE DECISION TO BLOW THE STATION DOWN. WHILE THE STATION WAS BLOWING DOWN, OPERATIONS PERSONNEL NOTICED THE BLOWDOWN WAS TAKING LONGER THAN IT TYPICALLY WOULD AND STARTED TO INVESTIGATE. OPERATIONS IDENTIFIED THAT THE SIDEGATE ACTUATOR HAD ONLY CLOSED 75% OF THE WAY. AS A RESULT, TWO OF THE STATION BLOWDOWN VALVES (3"" AND 8"" PLUG VALVES) WERE VENTING MAINLINE PRESSURE GAS TO THE ATMOSPHERE FROM THE TIME THE ESD SYSTEM WAS ACTIVATED TO THE TIME THE SIDEGATE WAS MANUALLY CLOSED BY OPERATIONS PERSONNEL. IT IS ESTIMATED THAT IT TOOK OPERATIONS 15 MINUTES BETWEEN ORIGINAL ESD ACTIVATION AND COMPLETE SHUT IN OF THE MALFUNCTIONING SIDE GATE VALVE AND COMPRESSOR STATION. ONCE THE SIDEGATE WAS PROPERLY CLOSED, AND THE STATION WAS SHUT IN FROM THE MAINLINE, A PROPER ESD WAS SUCCESSFULLY EXECUTED. IT WAS IDENTIFIED THAT THE SIDEGATE VALVE ACTUATOR DID NOT PROPERLY SHUT THE VALVE AS A RESULT OF THE ACTUATOR CONTROLS MALFUNCTIONING DUE TO THE WATER EXPOSURE IN THE CONTROL ROOM. SINCE THE INCIDENT ALL AFFECTED CONTROL SYSTEMS HAVE BEEN REPLACED.