EQUITRANS MIDSTREAM CORPORATION

Incident Narrative

ON 1/29/19 A RUPTURE OCCURRED ON THE MAINLINE OF H312 PIPELINE. THE FAILURE WAS LOCATED AT A GIRTHWELD OF AN ELBOW AND MAINLINE PIPE. THE PIPE AND COATING INFORMATION IS IN PART C OF THIS REPORT. THE FITTING INFORMATION IS 12.75"", 0.375 WT, Y52. THE COATING FOR THE WELD WAS DENSO 7200. THE ROOT CAUSE INVESTIGATION FOUND THAT A LANDSLIDE ABOUT 150 YARDS FROM THE RUPTURE MOVED THE PIPELINE FROM IT'S ORIGINAL LOCATION APPROXIMATELY 10 FEET AND PLACED STRESSED ON THE WELD AT THE ELBOW. THE WELD WAS SENT OUT FOR ANALYSIS. THE NDT READER SHEET SHOWS THE X-RAY FOR THE WELD PASSED. THE HYDROTEST PERFORMED DURING CONSTRUCTION WAS SUCCESSFUL. TIMELINE DATE: 1/29/2019 1:03 PM CYBERTEL (ANSWERING SERVICE FOR EMERGENCY NUMBER) CALLED OPERATION FIELD TECH ABOUT POTENTIAL LEAK 1:36 PM XTO CALLED INTO EQUITRANS GAS CONTROL ABOUT POTENTIAL LEAK ON H312 1:49 PM H312 PIPELINE ISOLATED 2:30 PM EQUITRANS MIDSTREAM COMPLIANCE DEPARTMENT NOTIFIED OF POTENTIAL LINE RUPTURE 2:51 PM EQUITRANS OPERATIONS FIELD PERSONNEL PERFORMED A VISUAL CONFIRMATION OF INCIDENT 4:25 PM NATIONAL RESPONSE CENTER NOTIFIED OF INCIDENT METALLURGICAL ANALYSIS SHOWED HIGH APPLIED AXIAL STRESS (LAND/SOIL MOVEMENT) ACTING ON A GIRTHWELD. THE GIRTHWELD SHOWED SOME PRE-EXISTING HYDROGEN ASSISTED COLD CRACKS OR HYDROGEN EMBRITTLEMENT, WHICH FORMED OVER TIME AS A RESULT OF HYDROGEN IN THE WELD OR A COMBINATION OF THESE TWO PROCESSES. WITH CONSULTATION, THESE CRACKS WERE STABLE UNDER HOOP STRESS BUT BECAME UNSTABLE WITH THE ADDED AXIAL STRESS. A LANDSLIDE WAS OBSERVED APPROXIMATELY 100 YARDS FROM THE FAILURE LOCATION PERPENDICULAR TO THE PIPE ON A SIDE HILL.