NORTHWEST PIPELINE CORP (WGP)

Incident Narrative

UNIT SUCTION VALVE WAS NOT FULLY CLOSED AGAINST THE MECHANICAL STOP EVEN THOUGH THE WESTLOCK INDICATOR SHOWED CLOSED. WHEN UNIT PRESSURIZED HOLD STATUS TIMED OUT THE UNIT VENT VALVE OPENED ALLOWING GAS TO FLOW THROUGH UNIT SUCTION VALVE. WHILE SETTING THE LIMIT SWITCHES ON THE NEW SUCTION VALVE THE VALVE OPERATOR SOLENOIDS WERE ENERGIZED LOCALLY WITH A PORTABLE POWER SUPPLY INSTEAD OF USING THE HMI. THE LIMIT SWITCHES WERE CHECKED WITH A FLUKE TO VERIFY THEY WERE GETTING A CLOSED CONTACT STATUS. WHILE THIS WAS BEING DONE THE VALVE WAS ALSO CHECKED TO VERIFY THE VALVE WAS TRAVELING ALL THE WAY TO THE MECHANICAL STOPS. THE VALVE WAS COMMISSIONED WITH ZERO GAS PRESSURE. THE VALVE STATUS WAS NOT VERIFIED USING THE UNIT HMI TO SEND OPEN AND CLOSED COMMANDS AFTER THE UNIT WAS PURGED AND PACKED. DISTRICT: WESTLOCK LIMIT SWITCH SHOWED VALVE CLOSED WHEN IT WAS STILL 10% ~ OPEN. LIMIT SWITCH ADJUSTED AND TESTED. OPERATES CORRECTLY GAS CONTROL ACTIONS: IT WAS CONCLUDED THAT THE CONTROLLERS FAILURE TO RESPOND TO A LOW-LUBE OIL & A UNIT COOL DOWN LOCKOUT ALARM IS OF GREAT CONCERN & IS CLEARLY A BREACH OF GAS CONTROLS PROTOCOL. THESE ALARMS WERE SECONDARY TO GAS BEING VENTED BUT FOLLOWING PROTOCOL REGARDING THESE ALARMS MAY HAVE FOUND THE PROBLEM MUCH SOONER.