CONSUMERS ENERGY CO

Incident Narrative

AT APPROXIMATELY 1:34 AM, BLOWDOWN VALVE 613 AT FREEDOM COMPRESSOR STATION TRAVELED OPEN AND VENTED GAS TO ATMOSPHERE THROUGH THE STATION EMERGENCY SHUT-DOWN VENT FOR APPROXIMATELY 1 HOUR AND 23 MINUTES. IN TOTAL, 34 MMCF WAS VENTED TO ATMOSPHERE. AFT THE INCIDENT, THE VALVE OPERATOR MANUFACTURER'S REPRESENTATIVE (WILSON VALVE SPECIALTIES) WAS CONTACTED FOR TESTING METHODS. THE BIFFI 745 PILOT CONTROL VALVE WAS TESTED PER THESE VERBAL INSTRUCTIONS. NO DEFECTS WERE FOUND DURING TESTING, AND THE VALVE WAS PLACED BACK IN SERVICE. AN INVESTIGATION TEAM WAS SUBSEQUENTLY FORMED TO EVALUATE THE INCIDENT; THE TEAM CONVENED SEPTEMBER 5TH, 2012. AS A RESULT OF THIS INVESTIGATION, THE PILOT CONTROL VALVE WAS TO BE REMOVED AND SENT FOR FURTHER TESTING ON SEPTEMBER 7TH, 2012, AT WHICH POINT A SECOND VENTING INCIDENT OCCURRED (NRC REPORT #1023618). THE VENDOR (WILSON VALVE SPECIALTIES) WAS CONTACTED AGAIN BY INVESTIGATION TEAM MEMBERS TO DETERMINE WHETHER THEY WERE AWARE OF SUCH INCIDENTS ON SIMILAR BLOWDOWN VALVES. THEY INDICATED ONE SUCH VENTING INCIDENT IN WISCONSIN, AND INDICATED THAT A MODIFICATION HAD BEEN SUBSEQUENTLY MADE TO THE VALVE IN QUESTION TO HOUSE THE PILOT VALVE IN A WEATHER-TIGHT ENCLOSURE IN ORDER TO PROTECT IT FROM WEATHER CONDITIONS. NEW VALVE ASSEMBLIES, WITH WEATHER ENCLOSURES PROTECTING THE PILOT VALVE AS WELL AS THE CONTROLLER, WERE THEN ORDERED FOR VALVE 613 AND THREE OTHER SIMILAR VALES AT THE STATION. THESE ASSEMBLIES HAVE BEEN INSTALLED AND ALL VALVES APPEAR TO BE FUNCTIONING AS DESIGNED. TESTING OF THE REPLACED VALVE 613 ASSEMBLY BY WILSON HAS SINCE REVEALED A SMALL SEAL LEAK ON THE BIFFI 745 PILOT CONTROL VALVE, AS WELL AS PLUGGED VENTS, WHICH LIKELY CONTRIBUTED TO THE VENTING INCIDENTS.