UGI ENERGY SERVICES

Incident Narrative

"ON MARCH 20, 2025, COMPRESSOR #2 WAS PLACED IN MAINTENANCE MODE FOR TROUBLESHOOTING AN ESD VENT VALVE STATUS ISSUE. LOOSE TERMINALS IN THE ACTUATOR CONTROL BOARD WERE IDENTIFIED AND REPAIRED. HOWEVER, MAINTENANCE MODE WAS ACCIDENTALLY LEFT ACTIVE OVERNIGHT. THE MAINTENANCE MODE SHOULD HAVE TRIGGERED LOCAL ALARMS AND SMS NOTIFICATIONS AT 2, 12, AND 24 HOURS, BUT SMS ALERTS FAILED TO GENERATE. OPERATORS MISSED THE MAINTENANCE STATUS ON LOCAL SCADA DISPLAYS THE MORNING OF MARCH 21. AT 12:24 ON MARCH 21, COMPRESSOR #2 SUCTION AND DISCHARGE BLOCK VALVES UNEXPECTEDLY CLOSED. NORMALLY THIS WOULD TRIGGER UNIT SHUTDOWN, BUT MAINTENANCE MODE BLOCKED ALL SHUTDOWN SIGNALS, FORCING THE COMPRESSOR TO RUN WITH CLOSED VALVES UNTIL 13:05 WHEN OPERATORS RECEIVED A LOSS OF RUN STATUS ALARM. PERSONNEL ARRIVED AT 13:14 AND ASSESSED DAMAGE. DURING INSPECTION, A SMALL OIL FIRE WAS DETECTED BY THE SAFETY SYSTEM, CAUSING STATION ESD AT 13:23. OPERATIONS PERSONNEL IMMEDIATELY EXTINGUISHED THE FIRE. POST-INCIDENT SCADA ANALYSIS REVEALED BOTH VALVES OPENED WITHOUT COMMAND AFTER THE COMPRESSOR STOPPED. THE ENGINE CONTROL PANEL INDICATED SHUTDOWN DUE TO MECHANICAL OVERLOAD. THE VALVE CLOSURE CAUSED CATASTROPHIC MECHANICAL FAILURE REQUIRING COMPLETE REPLACEMENT OF FRAME, CRANKCASE, CRANKSHAFT, CYLINDERS, AND ASSOCIATED COMPONENTS. THE MAINTENANCE MODE CAPABILITY HAS BEEN ELIMINATED FROM STATION PLC PROGRAMMING. ROOT CAUSE WAS IDENTIFIED AS MALFUNCTION IN VALVE CONTROL CIRCUITRY, HARDWARE, WIRING, AND CONNECTIONS BETWEEN PLC AND VALVE ACTUATORS. DUE TO THE INTERMITTENT NATURE, SPECIFIC COMPONENT ISOLATION WAS IMPOSSIBLE DURING ONLINE OPERATION. INVESTIGATION ELIMINATED PLC PROGRAMMING AND HARDWARE, NARROWING THE FAULT TO PHYSICAL CONNECTIONS INCLUDING I/O BOARDS, CABINET CONNECTIONS, AND FIELD WIRING. HISTORICAL REVIEW REVEALED SIMILAR VALVE CLOSURES PREVIOUSLY MISDIAGNOSED AS PNEUMATIC ISSUES. PRIOR TO RESTART, ALL PLC I/O BOARDS FOR BLOCK VALVE CONTROL WERE REPLACED, WIRING CONTINUITY VERIFIED, AND ACTUATOR TERMINATIONS INSPECTED. SINCE RETURNING TO SERVICE APRIL 29, 2025, NO UNEXPECTED VALVE POSITION CHANGES OCCURRED. COMBINED WITH REMOVAL OF PROBLEMATIC MAINTENANCE FUNCTIONS AND NEW MAINTENANCE MODE SAFEGUARDS, WE ARE CONFIDENT THE ROOT CAUSE IS RESOLVED AND SIMILAR ELECTRICAL FAILURES WOULD NOT RESULT IN THE SAME INCIDENT TYPE."