TC OIL PIPELINE OPERATIONS INC

Incident Narrative

ON DECEMBER 7, 2022, DURING AN IN-LINE INSPECTION TOOL RUN IN THE AREA, THE LIQUIDS PIPELINE CONTROL CENTER RECEIVED A LEAK DETECTION ALARM (VOLUME IMBALANCE) AT 21:01 CST, AN EMERGENCY-LINE TRIP ALARM WAS RECEIVED AT 21:07, AND THE CONTROLLER ISSUED THE COMMAND TO SHUT DOWN AND ISOLATE VALVES. TECHNICIANS WERE DISPATCHED TO VARIOUS AREAS BETWEEN THE STEELE CITY PUMP STATION AND 30 MILES DOWNSTREAM TO DETERMINE/CONFIRM A RELEASE EVENT. AT 00:15 DECEMBER 8, A CRUDE OIL ODOR WAS DETECTED BY A TCE TECHNICIAN WHICH CONFIRMED DISCOVERY OF A RELEASE AND THE NRC WAS CALLED AT 00:28. PIPELINE WAS SUBSEQUENTLY RESTARTED ON DECEMBER 29 AFTER REPLACEMENT OF FAILED SECTION. MECHANICAL AND METALLURGICAL TESTING ARE BEING PERFORMED BY AN INDEPENDENT TESTING FACILITY, AND A ROOT CAUSE FAILURE ANALYSIS (RCFA) WILL BE PERFORMED. 20230308 UPDATE: THE MECHANICAL AND METALLURGICAL REPORT IS COMPLETE AND IS INPUT INTO THE ONGOING RCFA. THE REPORT DETERMINED THAT A LACK OF FUSION ON THE INSIDE DIAMETER CAUSED STRESS CONCENTRATIONS THAT INITIATED TOE CRACKS WHICH PROPAGATED TO THE OUTSIDE DIAMETER OVER TIME. THE ESTIMATED VOLUMES OF COMMODITY RELEASED UNINTENTIONALLY AND RECOVERED HAVE BEEN UPDATED, AS WELL AS THE ESTIMATED COSTS. 20230517 UPDATE: THE RCFA WAS PUBLISHED ON APRIL 21, 2023. THE PRIMARY CAUSE OF THE RUPTURE WAS A PROGRESSIVE FATIGUE CRACK THAT ORIGINATED AT A GIRTH WELD CONNECTING A MANUFACTURED ELBOW FITTING TO THE PIPE CONSTRUCTED ACROSS MILL CREEK. THIS GIRTH WELD TRANSITIONED THE PIPE WALL THICKNESS FROM THE ELBOW FITTING TO THE ADJACENT PIPE JOINT AND WAS COMPLETED AT A FABRICATION FACILITY. THE RCFA CONFIRMED THE WELDING WORKMANSHIP WAS COMPLIANT WITH APPLICABLE CODES AND STANDARDS. DURING INSTALLATION, THE PIPE SEGMENT WAS SUBJECT TO INADVERTENT BENDING STRESSES SUFFICIENT TO INITIATE A CRACK AT A SHALLOW LACK OF FUSION FEATURE IN THE SUBJECT GIRTH WELD. BENDING STRESSES DURING INSTALLATION ALSO LED TO A DEFORMATION IN THE ELBOW FITTING AND A WRINKLE IN THE ADJACENT PIPE JOINT. FURTHER, THE DESIGN OF THE WELD TRANSITION CREATED A STRESS CONCENTRATION POINT, MAKING THE PIPE AT THIS LOCATION MORE SUSCEPTIBLE TO BENDING STRESSES. THIS RESULTED IN THE INITIATION OF A CIRCUMFERENTIAL CRACK IN THE WELD, WHICH LED TO FAILURE THROUGH OPERATING CYCLES OVER 11.5 YEARS. THE ESTIMATED VOLUMES OF COMMODITY RELEASED UNINTENTIONALLY AND RECOVERED HAVE BEEN UPDATED, AS WELL AS THE ESTIMATED COSTS. 20231102 UPDATE: ESTIMATED COSTS HAVE BEEN UPDATED.