CONSUMERS ENERGY CO

Incident Narrative

ON SEPTEMBER 22, 2016 AT APPROXIMATELY 08:33 THE ST. CLAIR PLANT II DISCHARGE HEADER FIREGATE BLOCK VALVE #604 AT CONSUMERS ENERGY ST. CLAIR COMPRESSOR STATION PLANT II UNEXPECTEDLY FAILED TO THE CLOSED POSITION DUE TO LOCAL LOSS OF ELECTRIC POWER TO THE ACTUATOR CONTROLS. CONSUMERS ENERGY 'S ST. CLAIR COMPRESSOR STATION IS LOCATED IN IRA, MICHIGAN (ST. CLAIR COUNTY). THE VALVE CLOSURE RESULTED IN A BLOCKED DISCHARGE FROM UNIT 2-4, WHILE IT WAS OPERATING. AS PRESSURE ON THE DISCHARGE LINE INCREASED TO 1430 PSIG, THE RELIEF VALVE ON THE DISCHARGE OF THE UNIT OPENED RELIEVING PRESSURE ON THE LINE TO 1255 PSIG. THE RELIEF VALVE CYCLED FOR APPROXIMATELY ONE HOUR PRIOR TO THE BLOCK VALVE BEING IDENTIFIED AS THE CAUSE OF THE FAILURE. THE VALVE WAS RETURNED TO THE OPEN POSITION, AND NORMAL OPERATION WAS CONTINUED AT APPROXIMATELY 10:06. A LOCAL INVESTIGATION DETERMINE A LOSS OF POWER CAUSED THE EMERGENCY SHUT DOWN (ESD) TO OPERATE AT THE STATION. THE ESD OPERATION TRIGGERED GATE VALVE #604 TO TRAVEL WHEN NOT INTENDED LEADING TO AN UNPLANNED GAS RELEASE. ADDITIONAL INCIDENT ANALYSIS CONCLUDED THE PRIMARY CAUSE OF THE POWER OUTAGE WAS ON-SITE ELECTRICAL RE-WORK BEING PERFORMED BY A SECOND PARTY CONTRACTOR INVOLVED IN THE STATION UPGRADE PROJECT.