CONSUMERS ENERGY CO

Incident Narrative

AT 0816 HOURS ON THURSDAY, SEPTEMBER 15, 2016, TWO EMPLOYEES WERE FOLLOWING A PROCEDURE TO REPLACE A SECTION OF PIPE AT FIREGATE BOX 2-4 AT FREEDOM COMPRESSOR STATION. TO ISOLATE THE LINE TO BE WORKED ON, THE PILOT GAS LINES BETWEEN THE PILOT ISOLATION VALVE AND PILOT GAS SOLENOID WERE REQUIRED TO BE VENTED. IN ORDER TO PERFORM THIS TASK, THE FIREGATE VENT VALVES NEEDED TO BE IMMOBILIZED, TO PREVENT THE UNINTENDED RELEASE OF GAS. THE NORMAL PROCEDURE TO COMPLETE THIS TASK IS TO ISOLATE THE LOCAL POWER GAS AT THE ACTUATOR, AND VENT THE LINE BETWEEN THE ISOLATION VALVE AND THE ACTUATOR, THEN ISOLATE THE PILOT GAS AT THE ACTUATOR, AND VENT THE LINE BETWEEN THE ISOLATION VALVE AND THE ACTUATOR. ALL POWER GAS LINES AND PILOT GAS LINES TO THE EMERGENCY SHUTDOWN VALVE ACTUATORS WERE ISOLATED, AND THE CREW BEGAN TO VENT THE PILOT LINES ON TWO OF THE VALVES, VALVE 612 AND VALVE 614. THIS RESULTED (AS DESIGNED) IN TWO FIREGATE VALVES (612 AND 614) TRAVELING TO 100% OPEN AND VENTING 3.484 MMCF OF NATURAL GAS FROM A 620 PSI LINE TO ATMOSPHERE THROUGH THE 16-FOOT VENT STACK, FROM 0816 HOURS TO 0825 HOURS. THE OPENED VALVES WERE MANUALLY CLOSED BY STATION PERSONNEL. AFTER RE-ASSESSMENT OF THE PROCEDURE AND SITUATION, STATION PERSONNEL RELIEVED PRESSURE OFF OF THE POWER GAS BETWEEN THE ISOLATION VALVE AND FIREGATE VENT VALVE ACTUATORS, AND THEN RELIEVED PRESSURE OFF THE PILOT GAS. THE REQUIRED SEQUENCE TO ISOLATE FIREGATE VALVES IS TO ISOLATE POWER GAS AND THEN PILOT GAS. THIS SEQUENCE WAS NOT OUTLINED IN THE PROCEDURE PROVIDED. A DETAILED REVIEW OF THE PROCEDURE WAS NOT COMPLETED BY ADDITIONAL ENGINEERING REPRESENTATION FROM GAS COMPRESSION OPERATIONS, AND A PHYSICAL WALK-DOWN OF THE EQUIPMENT WAS NOT PERFORMED BY THE SITE FIELD LEADER, PRINCIPAL FIELD LEADER, OR BY ASSIGNED CREW PRIOR TO PROCEDURE APPROVAL OR WORK PERFORMANCE.