COLUMBIA GAS TRANSMISSION, LLC

Incident Narrative

ON NOVEMBER 26, 2015, A COLUMBIA GAS TRANSMISSION, LLC (COLUMBIA) FACILITY WAS SUBJECT TO AN EVENT DUE TO AN UNINTENDED ACTIVATION OF AN INTERMEDIATE 4-IN RELIEF VALVE (RV) THAT EXCEEDED 3,000 MCF OF NATURAL GAS (MATERIAL). THIS RV IS LOCATED ON THE DISCHARGE LINE OF UNIT NO. 2 IN ARTEMAS COMPRESSOR STATION (CS). THIS FACILITY IS LOCATED NEAR THE TOWN OF ARTEMAS IN BEDFORD COUNTY, PENNSYLVANIA. COLUMBIA OWNS, OPERATES AND MAINTAINS THIS TRANSMISSION FACILITY. AFTER RECEIVING A CALL FROM COLUMBIA S MONITORING CENTER ABOUT A FAULT AT UNIT NO. 2, COLUMBIA OPERATIONS PERSONNEL RESPONDED TO THIS EVENT TO ADDRESS THE FAULTED UNIT. UPON REACHING THE SITE AND IDENTIFYING THE SOURCE OF THE BLOWING NOISE, COLUMBIA PERSONNEL ISOLATED THE PIPELINE TO PREVENT ADDITIONAL FLOW OF MATERIAL THROUGH THIS RV WHERE THE AREA WAS MADE SAFE AND SECURED. THERE WAS NO PRESENCE OF FIRE OR EXPLOSION IN LIEU OF THE MATERIAL RELEASE. THE INITIAL ASSESSMENT OF THIS INCIDENT INDICATED THAT A CONTRIBUTING FACTOR WAS A CHECK VALVE LOCATED UPSTREAM OF THE RV HAD FAILED TO OPERATE. HENCE, PROVIDING CONTINUOUS FLOW TO THE RV, WHICH IN TURN CONTINUED TO RELIEVE THE ADDITIONAL FLOW (AS IT WAS DESIGNED TO). UNIT NO. 2 AND THE ASSOCIATED PIPING WERE KEPT ISOLATED PENDING FURTHER INVESTIGATIONS, WHEREAS THE REST OF THE FACILITY WAS KEPT RUNNING IN ITS NORMAL OPERATIONAL MODE. THE FAILURE ANALYSIS INVESTIGATION REPORT IDENTIFIED AN ELEVATED LEVEL OF VIBRATION MAY HAVE BEEN A CONTRIBUTING FACTOR THAT TRIGGERED THE FAILURE OF THE HEADER CHECK VALVE (CV), HENCE INITIATING THE CHAIN OF EVENTS. THE CV FUNCITONS AS ASEPARATOR BETWEEN THE INTERMEDIATE DISCHARGE HEADER FROM THE HIGH PRESSURE DISCHARGE HEADER. AS A CORRECTIVE ACTION, ADDITIONAL BRACING WAS INTRODUCED TO THE SUSPECT SUBJECT PIPING TO ATTENUATE THE VIBRATION.