COLUMBIA GAS TRANSMISSION, LLC

Incident Narrative

A RELIEF VALVE (RV) SITUATED ON UNIT NO. 2 DISCHARGE LINE IN SMITHFIELD COMPRESSOR STATION (CS) , WAS INADVERTENTLY ACTIVATED, RELEASING AN AMOUNT OF NATURAL GAS (MATERIAL) EXCEEDING 3,000 MCF. SMITHFIELD CS IS A TRANSMISSION CS THAT IS OPERATED AND MAINTAINED BY COLUMBIA GAS TRANSMISSION, LLC. THE CS IS LOCATED IN WETZEL COUNTY, NEAR THE TOWN OF SMITHFIELD, WEST VIRGINIA. THE STAINLESS-STEEL SENSING LINE ON THE RV HAD FAILED LEADING TO A FALSE INDICATION OF A PRESSURE DIFFERENTIAL AND ACTIVATING THE RV. THE UNINTENDED RELEASE OF MATERIAL WAS CALCULATED TO REACH 10,952 MCF. THE AUTOMATION AND ELECTRICAL ENGINEERING DEPARTMENT WITH THE COMPRESSION GROUP HAD ASSESSED THE EVENT AND IDENTIFIED THAT THE SENSING LINE HAD FAILED ON THE RV DUE TO EXCESSIVE VIBRATION TRANSMITTED BY THE OPERATING RECIPROCATING UNIT. A CORRECTIVE ACTION WAS ISSUED TO THE CS OPERATING PERSONNEL TO ALTER (REDUCE) THE SPEED ON THE RUNNING RECIPROCATING UNITS, TO REDUCE THE VIBRATION TO ACCEPTABLE LEVELS. IN ADDITION, THE EXISTING RVS IN SMITHFIELD CS ON THE DISCHARGE LINES OF UNITS 1 & 2, WERE RELOCATED TO ANOTHER LOCATION. IMPROVED PIPELINE PIER SUPPORTS, WERE ALSO INSTALLED THROUGHOUT INSTALLATION ACROSS THE FACILITY. A CONTINUED VIBRATION MONITORING SURVEY WAS ALSO INTRODUCED TO THE CS' TWO RECIPROCATING UNITS. CURRENTLY, THE TWO RECIPROCATING UNITS ARE IN IDLE SERVICE AND HAVE NOT BEEN OPERATING FOR AN EXTENDED PERIOD OF TIME. THE TWO TURBINE UNITS ARE PROVIDING THE REQUIRED COMPRESSION SERVICE FOR THE PIPELINE SYSTEM. A SAFETY ALERT WAS ISSUED TO CS OPERATORS TO BE ALERT FOR SIMILAR CIRCUMSTANCES SO THAT CORRECTIVE MEASURES CAN BE IMPLEMENTED TO PREVENT SIMILAR SENSING TUBE FAILURES FROM RE-OCCURRING.