COLUMBIA GAS TRANSMISSION CORP

Incident Narrative

ON SEPTEMBER 28, 2011, THE COMPRESSOR STATION ENGINEER DISCOVERED THAT THE 2-INCH VENT PIPE WAS BLOWING NATURAL GAS WHEN HE ARRIVED AT THE SITE. HE MANUALLY TRIPPED THE SOLENOID VALVE TO SHUT-OFF THE GAS FLOWING THROUGH THE VENT PIPE. THE COMPRESSOR STATION WAS IN BY-PASS MODE AND NOT OPERATING. INVESTIGATION OF THE EVENT RESULTED IN THE IDENTIFICATION OF A 'CAUSAL FACTORS' . THE ELECTRONIC ESD SYSTEM AT CORNING CS WAS UNNECESSARILY ACTIVATED. THE FUEL GAS ESD BLOCK VALVE DID NOT CLOSE AS DESIGNED . SINCE THE FUEL GAS BLOCK VALVE FAILED TO CLOSE, GAS FROM THE PIPELINE WAS VENTED FOR AN EXTENDED DURATION OF TIME. IN LIEU OF THIS INCIDENT AND ITS INVESTIGATION, SEVERAL CORRECTIVE ACTIONS WERE IMPLEMENTED AND EXECUTED AS FOLLOWS: 1. THE ETHERNET CONNECTION BETWEEN THE REMOTE I/O PANELS AND THE GUARDLOGIC PLC SHOULD BE ELIMINATED, OR A REDUNDANT ETHERNET COMMUNICATION BETWEEN THE REMOTE I/O PANELS AND THE GUARDLOGIC PLC SHOULD BE INSTALLED. HARD-WIRING THESE DEVICES MAY PROVIDE THE HIGHEST RELIABILITY. 2. INSTALL POINT-OF-USE FILTRATION ON ALL THE ESD OPERATOR CONTROLS THAT EMPLOY VERSA VALVES. IN ADDITION, IMPLEMENT THE MANUFACTURER'S RECOMMENDATION TO AVOID THE USE OF TEFLON-TAPE ON CONTROL TUBING FOR VERSA VALVES. THE SMALL DIAMETER OF THE INTERNALLY DRILLED PASSAGES OF THESE VALVES IS PRONE TO BLOCKAGE BY DIRT AND DEBRIS. 3. INSPECT THE CORNING CS VERSA VALVES AND OTHER SIMILAR SHUTTLE VALVES FOR CONTAMINATION BY DIRT AND DEBRIS.