NORTHERN BORDER PIPELINE COMPANY

Incident Narrative

AT 1728 ON JULY 31, 2012, THE STATION LOST UTILITY POWER WHEN A THUNDERSTORM WENT THROUGH THE AREA. THE FACILITY APU ATTEMPTED TO START AT WHICH TIME THE LEAD ACID BATTERIES EXHIBITED A CATASTROPHIC FAILURE LEAVING THE COMPRESSOR STATION WITHOUT 480 VAC POWER. AT 1742 THE UNIT SHUT DOWN DUE TO THE LACK OF LUBE OIL COOLING FANS WHICH OPERATE ON 480 VAC. AT 1747, WITHOUT OPERATING AIR COMPRESSORS DUE TO THE LACK OF 480 VAC, THE COMPRESSED AIR PRESSURE DECREASED TO A LEVEL WHERE THE UNIT NORMAL VENT VALVE (FAIL OPEN, SPRING ACTUATOR) FAILED ITS CLOSED POSITION AND BEGAN TO OPEN. THE UNIT EMERGENCY VENT VALVE OPENED (AS DESIGNED AND CONFIGURED IN THE UNIT PLC) AS A RESULT OF THE UNIT NORMAL VENT VALVE BEING OUT OF A POSITION. THE UNIT SUCTION AND DISCHARGE VALVES UTILIZE ELECTRIC OPERATORS (480 VAC) AND REMAINED OPEN IN THEIR PRE-EXISTING POSITION. THE STATION SUCTION AND DISCHARGE VALVES REMAINED OPEN AS THE EXISTING CONTROL LOGIC DID NOT ATTEMPT CLOSE THEM. AT 1900 THE STATION SUCTION AND DISCHARGE VALVES WERE CLOSED ON COMMAND BY THE RESPONDING TECHNICIAN. THE APU BATTERY ISSUE WAS ADDRESSED AND AUXILIARY POWER WAS RESTORED TO THE STATION. AT 2350 THE STATION WAS RETURNED TO OPERATIONAL STATUS. UTILITY POWER WAS RESTORED TO THE STATION.