COLUMBIA GAS TRANSMISSION, LLC

Incident Narrative

ON NOVEMBER 23, 2015, A COLUMBIA GAS TRANSMISSION, LLC (COLUMBIA) FACILITY WAS SUBJECT TO AN EVENT THAT INVOLVED AN UNINTENDED ACTIVATION OF AN 8-IN BLOW-OFF (BO) VALVE. THIS BO VALVE IS LOCATED IN RIPLEY COMPRESSOR STATION (CS) YARD. RIPLEY CS IS A TRANSMISSION FACILITY LOCATED NEAR THE TOWN OF SANDYVILLE, JACKSON COUNTY, WEST VIRGINIA IS OWNED, OPERATED AND MAINTAINED BY COLUMBIA. COLUMBIA OPERATIONS PERSONNEL RESPONDED TO THIS EVENT AND ISOLATED THE BO VALVE WITH ITS RESPECTIVE PIPELINE PREVENTING ADDITIONAL UNINTENDED RELEASE OF NATURAL GAS (MATERIAL) INTO ATMOSPHERE. THERE WAS NO PRESENCE OF FIRE, EXPLOSION OR EVACUATIONS IN LIEU OF THE MATERIAL RELEASE. THE INITIAL ASSESSMENT INDICATED THAT PRESENCE OF ACCUMULATED MOISTURE PLAYED A CONTRIBUTING FACTOR IN THE CHAIN OF EVENTS THAT LED TO THIS INCIDENT. THE EMERGENCY SHUTDOWN (ESD) SYSTEM TRIGGER PNEUMATIC PRESSURE ON THAT ACTUATOR BLED DOWN BELOW THE REQUIRED PRESSURE TO HOLD THE VALVE CLOSED. THE ESD PNEUMATIC PRESSURE TO ALL OTHER ESD VALVES REMAINED AT ITS FULL SYSTEM PRESSURE. AN ACCUMULATION OF APPROXIMATELY 2 GALLONS OF ACCUMULATED MOISTURE WAS DRAINED FROM THE ESD TRIGGER PNEUMATIC SUPPLY TANK, THAT IS LOCATED DIRECTLY DOWNSTREAM OF THE FACILITY'S AIR DRYER SYSTEM. A VENDOR TECHNICIAN WAS ON SITE THE FOLLOWING DAY OF THE INCIDENT WHERE A FULL ASSESSMENT TO THE AIR DRYER FOLLOWED. THE VENDOR'S TECHNICIAN IDENTIFIED THAT THE AIR DRYER SYSTEM'S AUTOMATIC CONTROL SYSTEM WAS LOCKED-UP. A MANUAL SWITCHING OPERATION WAS PERFORMED TO ENABLE THE FULL OPERATION OF THE TWO AIR DRYER SYSTEM TOWERS. THE ROOT CAUSE ANALYSIS (RCA) REPORT CONCLUDED THAT MOISTURE COLLECTED IN THE ESD TRIGGER PNEUMATIC TUBING FROZE WHICH ALLOWED THE PRESSURE ON THE ESD POPPET VALVE TO DECREASE TO THE POINT THAT THE VALVE TRIPPED AND THE BO VALVE OPENED. THE SOURCE OF MOISTURE WAS MOST LIKELY FROM THE ESD TRIGGER PNEUMATIC SUPPLY UNIT. ACCUMULATED MOISTURE WAS DISCOVERED IN THE ESD AIR STORAGE TANK. EVENTUALLY, THE CS AIR DRYER ALLOWED THE DEW POINT OF THE COMPRESSED AIR TO INCREASE. WHEN THE AMBIENT AIR TEMPERATURE DROPPED BELOW THE DEW POINT OF THE COMPRESSED AIR, THE WATER VAPOR CONDENSED IN THE ESD STORAGE TANK AND THE TRIGGER AIR PIPING. RECOMMENDATIONS: 1) COMPRESSOR STATIONS THAT USE A PNEUMATIC SYSTEM IN THEIR ESD SYSTEMS ARE RECOMMENDED TO CONSIDER INSTALLING A DEW POINT ANALYZER AT THE OUTLET OF THE AIR DRYER TO MONITOR PERFORMANCE AND PROVIDE AN ALARM OUTPUT TO THE CS CONTROLLER SO APPROPRIATE ACTIONS CAN BE TAKEN. 2) CONSIDER ADDING IN COLUMBIA'S WORK MANAGEMENT SYSTEM (WMS) A PREVENTIVE MAINTENANCE (PM) TASK TO THE ESD SYSTEM TO PERFORM AN ANNUAL PURGE TO THE PNEUMATIC SYSTEM AND VERIFY IF PRESENCE OF MOISTURE WAS IDENTIFIED. ALSO, CONSIDER THE ADDITION OF ANOTHER PM TO THE CRITICAL SHAFER ACTUATOR INSTALLATIONS TO INSPECT ROUTINELY THE SEALS FOR EVIDENCE OF DETERIORATION. SITE SPECIFIC: PER THE PROVIDED RECOMMENDATIONS IN THE RCA REPORT, A DEW POINT ANALYZER WITH CONTINUOUS FEEDBACK AND ALARM OUTPUT WAS INSTALLED WITH THE ADDITION OF THE APPROPRIATE PMS IN THE WMS.