COLUMBIA GAS TRANSMISSION CORP

Incident Narrative

A SHUTTLE VALVE HAD FAILED CAUSING AN UNINTENDED RELEASE OF NATURAL GAS TO VENT INTO ATMOSPHERE VIA AN 8-IN BLOW-OUT PIPE. THE COMPRESSOR STATION WAS SHUT DOWN TO STOP THE FLOW OF NATURAL GAS INTO ATMOSPHERE AND TO SECURE THE SITE FOR FURTHER INVESTIGATIONS. AN INVESTIGATIVE TEAM WAS LAUNCHED TO LOOK INTO THE PROBABLE CAUSE OF THIS INCIDENT. THE MANUFACTURER IS ASSISTING THE COMPANY ENGINEERING TEAM IN LOOKING INTO THE ROOT CAUSE OF THIS SHUTTLE VALVE FAILURE. ADDITIONAL INFORMATION WILL BE SUBMITTED IN THE FINAL INCIDENT REPORT. SUPPLEMENT/FINAL REPORT (SUBMITTED ON 02/28/2018 BY CHRIS LEGG) AN ONSITE INVESTIGATION WAS CONDUCTED ON 12/08/2011 FOLLOWING THE INCIDENT. THE ESD PILOT AIR POPPET VALVE, WHICH TRIGGERS THE ESD BLOWDOWN VALVE (8""), SOMETIMES REFERRED TO A ""SHUTTLE VALVE"", FAILED AFTER IT WAS STUCK IN THE OPEN POSITION. ED CLARKSON, WV PSC WAS ON-SITE DURING THE INVESTIGATION. DURING THE INVESTIGATION, SEVERAL SMALL LEAKS WERE LOCATED AROUND TUBING FITTINGS IN THE PILOT AIRLINE. POSSIBLE THAT PILOT LINE VENTED BETWEEN A FREEZE POINT AND THE TUBING LEAKS, WHICH THEN ALLOWED THE ACTUATOR TO GO OPEN. THE PILOT AIRLINE WAS DISASSEMBLED, BUT NO OBVIOUS SIGNS OF A FREEZE OR OTHER BLOCKAGE WAS SEEN. THE OTHER POSSIBILITY WAS THAT LIQUIDS IN THE POWER GAS FROZE INSIDE THE POPPET VALVE ASSEMBLY AND FORCED THE POPPET VALVE OPEN, WHICH THEN CAUSED THE ACTUATOR TO GO OPEN. AS A RESPONSE TO THE FAILURE, THE ESD PILOT AIR POPPET VALVE ON THE ACTUATOR WAS REBUILT AND FURTHER INSPECTED ON 12/13/2011 (MAXIMO WORK ORDER#: B2568587). AS A PREVENTATIVE MEASURE, ALL OF THE OTHER ESD PILOT AIR POPPET VALVES AT THE STATION WERE ALSO LATER REBUILD.