ENABLE OKLAHOMA INTRASTATE TRANSMISSION, LLC

Incident Narrative

ON OCTOBER 21, 2017 AT 00:15 ENABLE OKLAHOMA INTRASTATE TRANSMISSION LINE 25 EXPERIENCED A FAILURE IN WASHITA COUNTY OKLAHOMA. THE FAILURE OCCURRED AT THE GEORGE CREEK CROSSING IN THE SW 1/4 SECTION 25 T10N-R20W. THE FAILED SECTION OF LINE 25 WAS REMOVED AND SENT TO STRESS ENGINEERING SERVICES (SES) FOR METALLURGICAL ANALYSIS. AS OF THE DUE DATE FOR THIS REPORT, ENABLE MIDSTREAM PARTNERS HAS NOT RECEIVED THE RESULTS OF THE SES ANALYSIS FOR LINE 25. THE NRC WAS NOTIFIED ON 10/21/17 (NRC # 1193884). A 48 HR FOLLOW UP CALL WAS PROVIDED TO THE NRC ON 10/23/17 (NRC # 1194020) THE FAILURE INVESTIGATION IS ON-GOING. UPDATE 1/30/2018 A.18 EVACUATED CHANGED FROM 1 TO 0 C.3.B CHANGED .250 TO .257 C.3.E CHANGED LONGITUDINAL ERW - UNKNOWN FREQUENCY TO LONGITUDINAL ERW - HIGH FREQUENCY C.3.F UNKNOWN CHANGED TO STUPP D.7.A CHANGED 20,000 TO 17,000 D.7.B CHANGED 447,718 TO 550,000 D.7.C CHANGED 10,000 TO 5,000 E.5.C CHANGED FROM UNKNOWN TO 67,196 A FAILURE INVESTIGATION IS STILL ON-GOING. UPDATE 4/16/18 G5.1 CHANGED FROM ""FIELD EXAMINATION"" TO ""DETERMINED BY METALLURGICAL ANALYSIS"" G5.2 CHANGED FROM OTHER ""CONSTRUCTION"" TO OTHER ""EXCESSIVE BENDING LOADS"" G5.4 CHANGED ""LACK OF FUSION"" TO ""MISALIGNMENT"" G5.A CHANGED FROM ""OTHER - MFL COMBO"" TO ""COMBINATION TOOL"" G8.A CHANGED FROM ""NO"" TO ""YES"" ""RADIOGRAPHY (2017)"" AND ""HANDHELD ULTRASONIC TOOL (2017)"" THE INVESTIGATION IS COMPLETE. A METALLURGICAL ANALYSIS WAS PERFORMED INCLUDING VISUAL, FRACTOGRAPHIC, AND METALLOGRAPHIC EXAMINATION. VISUAL EXAMINATION REVEALED THAT THE MAJORITY OF THE FRACTURE OCCURRED ALONG THE EDGE OF THE GIRTH WELD IN THE HEAT AFFECTED ZONE. THE PIPES ON BOTH SIDES OF THE GIRTH WELD MEET THE DIMENSIONAL REQUIREMENTS OF API 5L AND NO SIGNIFICANT CORROSION WAS OBSERVED. THE SAMPLE CONTAINED A SAG BEND WHEREBY THE EXTRADOS OF THE BEND COINCIDED WITH THE 6:00 O'CLOCK ORIENTATION. THE FRACTURE PROPAGATED APPROXIMATELY TWO-THIRDS OF THE SAMPLE'S CIRCUMFERENCE AND ARRESTED IN THE BASE MATERIAL. FRACTOGRAPHIC AND METALLOGRAPHIC EXAMINATION REVEALED THAT THE SAMPLE FAILED DUE TO EXCESSIVE BENDING LOADS. THE TRANSITION WELD AND LACK OF PENETRATION DUE TO HIGH-LOW AT THE ROOT OF THE WELD ACTED AS A STRESS CONCENTRATOR AND THE FAILURE ULTIMATELY INITIATED AT THE BASE OF THIS FEATURE.