COLUMBIA GULF TRANSMISSION, LLC

Incident Narrative

ON MAY 10TH, 2014, A COLUMBIA GULF TRANSMISSION, LLC (COLUMBIA) CORINTH COMPRESSOR STATION (CS) PERSONNEL ARRIVED ON SITE AND NOTICED THAT A RELIEF VALVE (RV) WAS UNINTENTIONALLY RELIEVING A MINUTE AMOUNT OF NATURAL GAS INTO ATMOSPHERE. THE COLUMBIA PERSONNEL INVESTIGATED THE AREA AND ISOLATED THE RV FOR FURTHER INVESTIGATION INTO THE REASON BEHIND THIS UNINTENDED RELEASE. AFTER ENGAGING ENGINEERING PERSONNEL INTO THE INVESTIGATION, IT WAS IDENTIFIED THAT AT THE TIME THE CS WAS REMOTELY SHUTDOWN, ALL BLOWDOWN VALVES FUNCTIONED AS THEY WERE DESIGNED TO. HOWEVER THE SUBJECT RV WAS MODULATING THE FLOW AND ACTING SIMILAR TO A REGULATOR VALVE RATHER THAN A RV. IT WAS IDENTIFIED THAT THE PRESSURE DIFFERENTIAL WAS SO MINUTE TO AN EXTENT THAT IT ALLOWED TO UNSEAT THE VALVE AND UNINTENTIONALLY RELEASING MATERIAL INTO ATMOSPHERE. THE PILOT CONTROL PRESSURE WAS NOT REQUIRED TO BE INSTALLED ON THE UPSTREAM SIDE OF THE INSTALLATION OF THE CS UNIT SUCTION HEADER. HENCE, IT WAS RELOCATED AND A RECONFIGURATION TO SUCH INSTALLATION WAS EXECUTED ALONG THIS FACILITY. FURTHERMORE, A RECOMMENDED APPROACH WAS SHARED AMONG OTHER CS WITH SIMILAR INSTALLATIONS TO INSPECT AND RELOCATE THE PILOT CONTROLS SENSORS TO AVOID SIMILAR SITUATIONS THAT MAY LEAD TO SIMILAR EVENTS.