CONSUMERS ENERGY CO

Incident Narrative

ON JULY 12, 2020 AT APPROXIMATELY 00:17 HOURS CONSUMERS ENERGY GAS CONTROLLED RECEIVED SCADA ALARMS INDICATING MULTIPLE ENGINES WERE OFFLINE AT THE RAY COMPRESSOR STATION PLANT 3. THE FACILITY IS LOCATED AT 69333 OMO ROAD, ARMADA, MICHIGAN (MACOMB COUNTY). STATION PERSONNEL WERE NOTIFIED AND ARRIVE ONSITE AT APPROXIMATELY 00:47 HOURS AND CONFIRMED HIGH GAS LEL IN THE PLANT 3 COMPRESSOR BUILDING. STATION PERSONNEL THEN PROCEEDED TO DEPRESSURIZE UNIT 3-1 BY OPENING VALVES VGV-701 AND VGV-702. THE GAS LEVEL WITHIN THE COMPRESSOR BUILDING GRADUALLY DECREASED TO ZERO. IT WAS THEN CONFIRMED THAT UNIT 3-1 WAS THE CAUSE OF THE GAS LEAK. FOLLOWING THE INCIDENT, THE STATION PERSONNEL HAVE WORKED THROUGH DISCOVERY ON THE UNIT BY DISASSEMBLING THROW #3 ON UNIT 3-1, AS WELL AS INSPECTING THE INTEGRITY OF THE OTHER THROWS. AT THIS TIME THE DAMAGE IS ISOLATED TO THROW #3; HOWEVER, THE ROOT CAUSE HAS NOT BEEN IDENTIFIED. COMPONENTS OF THROW #3 HAVE BEEN SENT TO CONSUMERS ENERGY'S LABORATORY FOR FURTHER ANALYSIS TO ASSIST WITH THE IDENTIFICATION OF THE ROOT CAUSE OF FAILURE. THE INCIDENT INVESTIGATION AND LABORATORY ANALYSIS DETERMINED A SERIES OF FAILURES OCCURRED RESULTING IN THE RELEASE OF GAS WITH PROPERTY DAMAGE IN EXCESS OF $50,000. A MECHANICAL FAILURE ON UNIT 3-1 THROW 3 CAUSED BY LOSS OF TENSION OF THE CROSS HEAD BALANCE NUT WHICH ALLOWED THE PISTON AND ROD ASSEMBLY TO BACK OUT AND MAKE CONTACT WITH THE FIXED VOLUME CLEARANCE POCKET RESULTING IN FAILURE OF THE PISTON ROD. MAINTENANCE RECORDS FOR THE TORQUEING OF THE CROSS-HEAD BALANCE NUT WERE NOT AVAILABLE. THE EXCESSIVE VIBRATION THAT OCCURRED AS A RESULT OF THE MECHANICAL FAILURE CAUSED THE BOLTS ON THE SUCTION VALVE UNLOADER TO LOOSEN AND GAS TO BE RELEASED. THE SAFETY SYSTEM DESIGNED TO ISOLATE AND EVACUATED GAS THROUGH THE VENT VALVE DID NOT TRAVEL AUTOMATICALLY DURING THE EVENT AND INSTEAD REQUIRED MANUAL ACTIVATION. PROBLEM SOLVING WAS COMPLETED FOR THE MECHANICAL AND SAFETY SYSTEM FAILURES AND ACTION ITEMS DEVELOPED TO MINIMIZE FUTURE RE-OCCURRENCE. RESTORATION OF THE EQUIPMENT IS UNDERWAY, A FINAL REPORT WILL BE SUBMITTED WHEN THE NORMAL OPERATIONS IS RESUMED. FOLLOWING THE INCIDENT INVESTIGATION A COMPRESSOR RESTORATION PLAN WAS DEVELOPED FOR THROW #3. THE PLAN INVOLVED REPLACING THE PISTON ROD, PISTON, THE CROSSHEAD, BALANCE NUT, INNER-CYLINDER HEAD AND THE FIXED VOLUME CLEARANCE POCKET. THE SUCTION VALVE UNLOADERS WERE DISASSEMBLED, INSPECTED AND REBUILT. ACTIONS WERE ALSO TAKEN TO CORRECT THE VALVE POSITIONING ALLOWING THE SAFETY MECHANISM TO AUTOMATICALLY TRAVEL WHEN SPECIFIED PERCENTAGE OF GAS IS DETECTED IN THE BUILDING. FOLLOWING REMEDIATION NORMAL OPERATIONS WERE RESUMED ON DECEMBER 9, 2020.