COLUMBIA GAS TRANSMISSION, LLC

Incident Narrative

ON JULY 1, 2014, A COLUMBIA GAS TRANSMISSION, LLC (COLUMBIA) COMPRESSOR STATION (CS) LOCATED IN WETZEL COUNTY, WV UNDERWENT AN UNINTENDED RELEASE OF NATURAL GAS. THE CS IS SMITHFIELD, A TRANSMISSION FACILITY THAT IS OPERATED AND MAINTAINED BY COLUMBIA. THE FACILITY WAS SUBJECT TO AN EMERGENCY SHUTDOWN (ESD) DUE TO AN INADVERTENT ACTIVATION OF A SWITCH ON THE STATION CONTROL PANEL. THIS TOOK PLACE WHEN AN ELECTRICIAN WAS PERFORMING AN UPDATE TO THE PANEL. TRIPPING THE ESD SYSTEM, WITH AN EMERGENCY VALVE STUCK IN THE OPEN POSITION, LEADING TO AN UNINTENTIONAL RELEASE OF NATURAL GAS THAT VENTED INTO ATMOSPHERE. AN INSPECTION IDENTIFIED THE PROBABLE CAUSE LEADING TO THIS REPORTABLE INCIDENT WAS THE INADVERTENT ACTIVATION OF THE ESD. A DETAILED INVESTIGATION REVEALED THE INADVERTENT ACTIVATION OF THE ESD WAS CAUSED BY TWO APPARENT FACTORS. THERE WAS AN INTERRUPTION TO THE CONTROL CIRCUIT TO THE STATION AIR PRESSURE TRANSMITTER CAUSED BY AN ELECTRICAL CONTRACTOR WORKING IN THE STATION AIR COMPRESSOR CONTROL PANEL. A WIRE WAS INCORRECTLY REMOVED BETWEEN THE AIR PRESSURE TRANSMITTER AND THE PROGRAMMABLE LOGIC CONTROLLER CAUSING A LOSS OF PRESSURE DATA TO THE COMPRESSOR STATION CONTROL PANEL. DUE TO THE LOSS OF A PRESSURE READING, THE COMPRESSOR STATION AIR COMPRESSORS DID NOT OPERATE ALLOWING THE STATION AIR PRESSURE TO SLOWLY DECLINE TRIGGERING THE STATION ESD SYSTEM TO OPERATE. LOSS OF THE PILOT AIR PRESSURE CAUSED THE VENT VALVES TO PARTIALLY OR FULLY OPEN WITHOUT THE ESD BLOCK VALVES CHANGING POSITION AS DESIGNED. LEARNINGS FROM THIS INCIDENT INCLUDE HAVING STATION PERSONNEL CLOSELY REVIEW ANY FAULTS ON THE STATION CONTROL PANEL BEFORE CLEARING A STATION ALARM. ANY FAULTS OBSERVED WILL BE FULLY INVESTIGATED. STATION AIR PRESSURE SHOULD BE ROUTINELY CHECKED AND RECORDED. IN ADDITION, CERTAIN STATION FAULTS SHOULD NOT BE ALLOWED TO BE CLEARED WITHOUT A CAUSE OF THE FAULT BEING CORRECTED. FOR PART E, #1 ESTIMATED PRESSURE AT THE POINT AND TIME OF THE INCIDENT, THERE WERE TWO PRESSURES DUE TO THE VALVES VENTING INTO ATMOSPHERE. THE PRESSURES WERE 628 PSIG AND 836 PSIG.