EQUITRANS MIDSTREAM CORPORATION

Incident Narrative

AT APPROXIMATELY 1:40 A.M. ON AUGUST 14TH, 2022, GAS CONTROL RECEIVED A LOW FLOW ALERT FOR EQUITRANS' ZINK COMPRESSOR STATION. GAS CONTROL THEN NOTICED AN APPROXIMATE 250 PSIG DROP IN DISCHARGE PRESSURE ON COMPRESSOR #5 AT THE STATION. THE ON CALL OPERATION EMPLOYEE WAS DISPATCHED AND FOUND A RELIEF VALVE WAS VENTING AT THE STATION. THE RELIEF VALVE CEASED VENTING AT APPROXIMATELY 3:15 A.M. PRESSURE AT THE RELIEF VALVE AT THE TIME OF THE FAILURE WAS APPROXIMATELY THE STATION DISCHARGE PRESSURE OF 1521 PSIG. ONCE THE RELIEF VALVE BEGAN VENTING, THE PRESSURE AT THE RELIEF VALVE DROPPED TO THE STATION SUCTION PRESSURE OF APPROXIMATELY 1040 PSIG. A CALCULATION WAS PERFORMED AND IT WAS DETERMINED THAT THE GAS LOSS EXCEEDED THE 3 MILLION CUBIC FOOT THRESHOLD FOR REPORTING AS PER CFR49 PART 191.3. AFTER FURTHER REVIEW, IT WAS DETERMINED THAT AN O-RING FAILED IN THE VALVE SEAT WHICH IS COMMONLY CAUSED BY VIBRATION. THE INITIAL INTERPRETATION WAS THAT A 48 NOTICE WAS REQUIRED ONLY WHEN CHANGES TO REPORTED DATA WERE KNOWN, BUT IT HAS SINCE BEEN UNDERSTOOD THAT A 48 HOUR NOTICE IS REQUIRED ON ALL INCIDENTS EVEN IF IT JUST CONFIRMS THE INITIAL REPORTED DATA.