CONSUMERS ENERGY CO

Incident Narrative

ON FEBRUARY 19, 2019 AT APPROXIMATELY 02:43 HOURS CONSUMERS ENERGY GAS CONTROL WAS NOTIFIED OF VENTING GAS AT RAY COMPRESSOR STATION. RAY COMPRESSOR STATION IS LOCATED IN ARMADA, MICHIGAN (MACOMB COUNTY). THE ON-CALL STATION MECHANIC WAS DISPATCHED AT 02:47 HOURS AND ARRIVED AT THE SITE AT APPROXIMATELY 03:26 HOURS AND GAS WAS NO LONGER VENTING. SECURITY CAMERAS AT THE STATION WERE USED TO DETERMINE THE APPROXIMATE LOCATION OF THE BLOWING GAS. UPON FURTHER INVESTIGATION THE SOURCE OF THE BLOWING GAS WAS DETERMINE TO BE THE PRESSURE RELIEF VALVE (PSV-00103) ON THE SLUG CATCHER. SUBSEQUENT REVIEW OF PRESSURE DATA INDICATES GAS BEGAN VENTING AT APPROXIMATELY 02:20 HOURS AND BLEW FOR APPROXIMATELY 37 MINUTES BEFORE PRESSURE READINGS NORMALIZED. AT APPROXIMATELY 06:30 HOURS THE SLUG CATCHER WAS ISOLATED TO FURTHER INVESTIGATE THE POTENTIAL CAUSE OF THE GAS RELEASE. DURING THE VISUAL INSPECTION, ICE IN THE PILOT SENSING LINE WAS IDENTIFIED AS A POTENTIAL CAUSE. AFTER CONSULTING WITH ENGINEERING THE DECISION WAS MADE TO ISOLATE THE SLUG CATCHER PRESSURE RELIEF VALVE AND RESUME NORMAL OPERATION OF THE SLUG CATCHER. ON FEBRUARY 20, 2019 AFTER CONTINUED INVESTIGATION AND ADDITIONAL ENGINEERING CONSULTATION, THE SLUG CATCHER WAS BLOWN DOWN AND REMOVED FROM SERVICE PENDING A ROOT CAUSE REVIEW. A ROOT CAUSE ANALYSIS (RCA) WAS CONDUCTED BY THE EXPERITEC, THE PRESSURE RELIEF VALVE MANUFACTURE, ON FEBRUARY 25, 2019. A SUMMARY OF THE INVESTIGATION RESULTS ARE AS FOLLOWS: BASED ON THE MULTIPLE CONFERENCE CALLS HELD WITH TAYLOR FORGE (VESSEL MANUFACTURER), CONSUMER ENERGY, EXPERITEC AND EMERSON IT IS OUR OPINION THAT THE EXTERNAL LOW AMBIENT TEMPERATURES AND INTERNAL WET CONDITIONS OF THE NATURAL GAS CAUSED THE SUBJECT RELIEF VALVE TO FREEZE AT VARIOUS POINTS WITHIN THE VALVE. THE FREEZING CAUSED THE VALVE TO OPEN BELOW IT DESIGNATED SET PRESSURE. THE MANUFACTURER RECOMMENDED THAT ALL FOUR (4) RELIEF VALVES BE HEAT TRACED AND INSULATED TO PREVENT THE POTENTIAL OF POSSIBLE FREEZING IN THE FUTURE. CONSUMERS ENERGY'S OPERATIONS HAVE BEEN PERFORMING THE RECOMMENDED REQUIREMENTS TO RETURN THE VESSEL TO SERVICE. THE ANTICIPATED RETURN TO SERVICE DATE IS MARCH 20, 2019. THE FOUR (4) RELIEF VALVES WERE HEAT TRACED AND INSULATED PER MANUFACTURER'S RECOMMENDATION ON MARCH 18, 2019. THE EQUIPMENT WILL RESUME NORMAL OPERATION AS NEEDED DURING THE 2019-2020 WITHDRAWAL SEASON.