CONSUMERS ENERGY CO

Incident Narrative

ON NOVEMBER 8, 2023, AT APPROXIMATELY 12:11 HOURS CONSUMERS ENERGY GAS CONTROL RECEIVED AN ALARM NOTIFICATION WHICH INDICATED A POSSIBLE FIRE AT THE ST. CLAIR COMPRESSOR STATION (PLANT 4 DEHYDRATION SYSTEM BUILDING). THE CONSUMERS ENERGY ST. CLAIR COMPRESSOR STATION IS IN IRA, MICHIGAN (ST. CLAIR COUNTY). A STATION MECHANIC AT THE SITE WAS NOTIFIED AND CONFIRMED ACTIVATION OF THE PLANT FIRE-GATE SYSTEM OCCURRED DUE TO THE FIRE DETECTION ALARM. FOLLOWING THE EVENT, THE PLANT WAS REMOVED FROM SERVICE AND THE SCENE WAS MADE SAFE. ADDITIONAL PERSONNEL WERE DISPATCHED TO THE STATION TO DETERMINE THE POTENTIAL CAUSE OF THE ACTIVATION. DURING THE INCIDENT INVESTIGATION, NO NOTABLE INDICATIONS OF FAILURES WERE PRESENT IN THE FACILITY, BUT UPON ARRIVAL, IT WAS NOTED THAT A GAP IN THE INSULATION ON THE REBOILER EXHAUST STACK WAS CLEARLY VISIBLE AND WAS PRESUMED TO BE THE SOURCE OF A FALSE TRIP INDICATION TO THE FIRE-EYE (IN DIRECT LINE OF SIGHT) DUE TO THE INFRARED IRRADIATION FROM THE PIPE (OPERATING AS NORMAL UP TO 1500 DEGREE F). THE INSULATION ON THE EXHAUST SYSTEM WAS INSPECTED WITH NO NOTABLE ISSUES OBSERVED, REPAIRED, AND RETURNED TO SERVICE ON NOVEMBER 9, 2023. ON NOVEMBER 10, 2023, AT APPROXIMATELY 11:17 HOURS, LESS THAN 24 HOURS AFTER THE RETURN TO SERVICE CONSUMERS ENERGY GAS CONTROL RECEIVED AN ALARM NOTIFICATION WHICH INDICATED A POSSIBLE FIRE AT THE ST. CLAIR COMPRESSOR STATION (PLANT 4 DEHYDRATION SYSTEM BUILDING). THE EQUIPMENT WAS TAKEN OFF-LINE, AND ALL INSULATION WAS REMOVED TO PERMIT PHYSICAL INSPECTION. SEVERAL CRACKED WELDS WERE IDENTIFIED ON THE EXHAUST LINE OF THE THERMAL OXIDIZER, SUPER HEATER, AND CONDENSATE COLLECTION SYSTEM OF THE THERMAL OXIDIZER. LOOSE BOLTS WERE FOUND IN THE FLANGED CONNECTIONS OF THE SYSTEM, AND AN EXHAUST PIPE SLIP JOINT CONNECTION TO THE EXHAUST STACK WAS FOUND TO NO LONGER BE INSERTED INTO THE FITTING. BOTH EVENTS WERE REPORTED TO MPSC AS REQUIRED WHEN AN EMERGENCY SHUTDOWN SYSTEM IS ACTIVATED, AND GAS RELEASED. HOWEVER, A MORE IN-DEPTH VISUAL INSPECTION CONFIRMED ADDITIONAL EQUIPMENT DAMAGE ANTICIPATED TO EXCEED PHMSA REPORTING CRITERIA OF $139,700. ADDITIONAL INVESTIGATIONS AFTER THE EVENT HAVE IDENTIFIED A CONCERN RELATIVE TO INSUFFICIENT BOLT TORQUE SPECIFICATIONS USED DURING A 2020 REPAIR TO THE SYSTEM, PIPE FABRICATION FAILURE RESULTING IN PRE-STRESS BEING APPLIED TO THE FAILED SYSTEM CONNECTION POINTS, AND POTENTIAL PINNED PIPE IN A HIGH THERMAL GROWTH AREA OF THE SYSTEM EXACERBATING STRESSES IMPARTED TO THOSE SAME CONNECTION POINTS. FURTHER PROBLEM SOLVING IS REQUIRED TO DETERMINE THE ROOT CAUSE OF THE FAILURE. HOWEVER, WITH THE CONCERNS DEFINED, CONSUMERS ENERGY HAS TAKEN ACTION TO REMEDIATE EACH CONCERN THROUGH A REFABRICATION OF THE SUPER HEATER VESSEL FAILED COMPONENTS, PIPE ASSEMBLIES FOUND TO BE CREATING THE PRE-STRESS SCENARIO, SLIP JOINT INSERTION WAS INCREASED TO AVOID RISK OF THE JOINT FAILING, APPLICATION OF TORQUE SPECIFICATIONS FROM THE ORIGINAL EQUIPMENT MANUFACTURER, AND IMPLEMENTATION OF A PREVENTATIVE MAINTENANCE SCHEDULE FOR RE-VALIDATING TORQUE ON BOLTED CONNECTIONS FOLLOWING RETURN TO SERVICE. FURTHER ANALYSIS IS REQUIRED TO SUPPORT CONFIRMATION OF THE PIPE FAILURE MODES IDENTIFIED IN THE FIELD AND IS PRESENTLY UNDERWAY. THE ORIGINAL EQUIPMENT MANUFACTURER HAS BEEN ENGAGED IN THE REVIEW AND REPAIR PLAN AND IS SUPPORTING REVIEW OF THE STRESS ANALYSIS. ENGINEERING SUPPORT HAS BEEN CONTRACTED TO SUPPORT MODEL DEVELOPMENT OF THE SYSTEM AND EXECUTE A PIPE STRESS ANALYSIS. FOLLOWING THE OUTCOME OF THE MODELING AND VALIDATION OF THE FAILURE MODES, ADDITIONAL STEPS MAY BE NECESSARY TO IMPROVE THE INTEGRITY OF THE SYSTEM AND WILL BE IMPLEMENTED ACCORDINGLY. FURTHER ANALYSIS CONFIRMED THE FAILURE WAS A RESULT OF INSUFFICIENT BOLT TORQUE SPECIFICATIONS PROVIDED BY THE MANUFACTURER DURING A PREVIOUS REPAIR TO THE SYSTEM. THE FAILURE WAS A RESULT OF THE BOLTS YIELDING AND TORQUE WAS LOST THROUGH THE THERMAL CYCLE CAUSING BOLTS TO LOOSEN.