COLORADO INTERSTATE GAS CO

Incident Narrative

ON 11/18/2022, AT 09:37, A 3 INCH EMERGENCY SHUT DOWN (ESD) VALVE UNINTENTIONALLY OPENED AT THE COLORADO INTERSTATE GAS (CIG), MUDDY GAP COMPRESSORS STATION. AT 22:14, CIG GAS CONTROL CALLED THE FIELD OPERATOR ON DUTY AND COMMUNICATED THAT PRESSURE WAS TRENDING DOWN AND A VENT VALVE MAY BE OPEN AT THE MUDDY GAP COMPRESSOR STATION. AT 23:30, CIG FIELD OPERATOR ARRIVED ON SITE AND DISCOVERED AN ESD VALVE WAS OPEN. THE OPERATOR CLOSED THE VALVE. THE INCIDENT WAS DEEMED REPORTABLE. THE NRC NOTIFICATION WAS ISSUED, AND THE INTERNAL INVESTIGATION STARTED. THE INTERNAL INVESTIGATION CONCLUDED THAT THE ESD VALVE SOLENOID FAILED DUE TO AN ACCUMULATION OF WATER AND DEBRIS FROM THE STATION SUPPLY AIR SYSTEM THAT FROZE CAUSING THE VALVE TO OPERATE ABNORMALLY SENDING A PNEUMATIC OPEN SIGNAL TO THE ESD VALVE. IN ADDITION, THE VALVE STATUS WAS NOT IN SCADA AND THE CONTROLLERS DID NOT GET AN ALARM NOTIFYING THEM THAT THE VENT VALVE WAS OPEN. IN ORDER TO PREVENT REOCCURRENCE CIG OPERATIONS CLEANED AND RE-TESTED THE VALVE SOLENOID. OPERATIONS IS REVIEWING PROCESSES AND PREVENTIVE MAINTENANCE MEASURES TO VERIFY THAT THE MUDDY GAP CS SUPPLIED AIR SYSTEMS ARE DRY THROUGHOUT THE ENTIRE SYSTEM. IN ADDITION, OPERATIONS ADDED VALVE STATUS PLC LOGIC ALARMS IN SCADA FOR THE MUDDY GAP ESD VALVES.