COLUMBIA GAS TRANSMISSION, LLC

Incident Narrative

A RELIEF VALVE (RV) WAS ACTIVATED AND RELEASED AN UNINTENDED AMOUNT OF MATERIAL INTO ATMOSPHERE AT A COLUMBIA GAS TRANSMISSION, LLC (COLUMBIA) COMPRESSOR STATION (CS) FACILITY IN PERRYSVILLE, OH. THIS CS IS OWNED, OPERATED AND MAINTAINED BY COLUMBIA. WHILE THE RV WAS STILL RELIEVING MATERIAL, THE 2-IN PIPELINE THAT THIS RV WAS INSTALLED ON WAS BROKEN. THIS STAND-OFF STEEL PIPE IS OF 2-IN DIAMETER WITH A WALL THICKNESS OF .218-IN. WAS FOUND BROKEN-OFF AT ITS LOWER SECTION (CLOSE TO THE PIPELINE THIS RV IS PROTECTING) AND SEPARATING THE RV FROM ITS PIPE. THE BROKEN 2-IN PIPE WAS REMOVED AND SENT TO A METALLURGICAL INVESTIGATION FAILURE CONSULTANT FOR FURTHER ANALYSIS AND INVESTIGATION. PRIOR TO THE MATERIAL RELEASE, THE CS UNITS WERE SHUT DOWN AS FLOW FROM THE STORAGE FIELD WAS NOT REQUIRED TO MAINTAIN CUSTOMER DEMAND. WHEN THIS OCCURS, DEPENDING ON STORAGE VOLUME, THE PIPELINE PRESSURE GRADUALLY INCREASED UP TO THE PREVAILING STORAGE FIELD WELL PRESSURE. AT THE TIME, THE COMPRESSOR STATION PIPING AND VALVING WAS CONFIGURED TO ALLOW THIS PRESSURE RISE INTO THE CS SUCTION PIPING WHICH HAS TWO RELIEF VALVES SET AT 720 PSIG. ONE RV ACTUATED AND VENTED AS INTENDED; AND KEPT THE SUCTION PIPING PRESSURE FROM INCREASING FURTHER. RESULTS OF METALLURGICAL FAILURE ANALYSIS INDICATE THAT THE CAUSE OF THE 2-IN DIAMETER PIPE FAILURE WAS FATIGUE AS A RESULT OF CYCLIC BENDING. AS A PREVENTIVE MEASURE TO PREVENT THE CHAIN OF EVENTS FROM RE-OCCURING IN THE FUTURE, A SUPPORT WAS INTRODUCED TO THE RV-PIPE ASSEMBLY WHERE IT WILL DIS-ALLOW THE RV VENT STACK FROM SWAYING, HENCE, DAMPENING THE CYCLIC EFFECT THAT LED TO THIS INCIDENT. SIMILAR INSTALLATION WAS APPLIED ON A SIMILAR APPLICATION WITHIN THE SAME FACILITY.