COLORADO INTERSTATE GAS CO

Incident Narrative

JANUARY 6, 2017: THERE WERE -40 F AMBIENT TEMPERATURES IN WAMSUTTER WY. COLORADO INTERSTATE GAS (CIG) WAMSUTTER COMPRESSOR STATION VENT VALVES (VO14, VO26, AND VO39) OPENED DUE TO A PNEUMATIC CONTROL MALFUNCTION CAUSED BY THE EXTREME COLD TEMPERATURES. 1:50 / 1:55A - VO14 AND VO26 VALVE ALARMS CAME INTO CIG GAS CONTROL. 2:02A - WAMSUTTER STATION UNIT #2 SHUTDOWN ON LOW SUCTION. 2:03A - GAS CONTROL DISPATCHED ON-CALL PERSONNEL. 2:30A - OPERATOR ARRIVED AT THE RAWLINS STATION AND ATTEMPTED TO CLEAR THE ALARMS. 4:45A - OPERATIONS PERSONNEL ARRIVED ON-SITE (WAMSUTTER STATION), ASSESSED THE SITUATION, DETERMINED THAT THE THREE VENT VALVES WERE RELEASING GAS. 4:50A - ALL VENT VALVES MANUALLY CLOSED. 5:26AM THE RELEASE WAS ESTIMATED TO EXCEED THE REPORTABLE UNINTENTIONAL GAS LOSS AMOUNT OF 3,000MCF. OPERATIONS SUPERVISOR CALLED GAS CONTROL TO INITIATE AN EMERGENCY RESPONSE LINE (ERL) CALL. THE INVESTIGATION DETERMINED THAT EXTREME COLD TEMPERATURES CAUSED THE PNEUMATIC CONTROL SYSTEM TO FAIL ON THREE WAMSUTTER STATION VENT VALVES. THE POWER GAS MIGRATED PAST THE INTERNAL COMPONENTS AND PRESSURED UP THE BACK SIDE OF THE CONTROL BLOCK, WHICH CAUSED THE VALVES TO OPEN. CIG WILL INSTALL HEAT TRACE AND BLANKETS ON THE ESD BLOCK VALVES AND VENTS TO PREVENT A REOCCURRENCE. NOTE THAT THE DATE OF INSTALLATION (PART C-4), PIR QUESTION (PART D-3), AND MAOP ESTABLISHED (PART E-2(A)) ARE BASED ON VALVE VO14, THE LARGEST VALVE. THE OTHER TWO VALVE INFORMATION IS AS FOLLOWS: V026 WAS INSTALLED IN 1996, AND VO39 WAS INSTALLED IN 2000. THE MAOP FOR THE ASSOCIATED PIPELINE FOR EACH VALVE WAS ESTABLISHED USING 49CFR 192.619(A)(2).