The detection, characterization, and sizing of seam anomalies continues to be a challenge for both in-line and in-the-ditch inspection technologies. This paper presents a testing program developed to evaluate the fatigue performance on a planar manufacturing defect removed from service in high frequency electric resistance welded (HF ERW) pipe. This defect was identified in the field by in-line inspection (ILI) and confirmed in the lab by phased array UT. In addition to the manufacturing flaw, several artificial flaws were sized and placed in the seam weld to evaluate the fatigue performance of the HF ERW seams. Fatigue was simulated in all flaws through a pressure cycle and surge test program based on the pipeline operational characteristics. At the conclusion of testing, a metallurgical evaluation analyzed the defect fatigue performance, and was compared to the original ILI and phased-array UT data. The metallurgical evaluation also characterized the fatigue growth and provided comparisons to analytical crack growth estimates. This work provides insight into the fatigue performance of early vintage HF ERW seams and comparisons between ILI and NDE sizing methods.
Denowh, C., Alexander, C.R., Schott, T., Chapman, B., “Fatigue Performance Characterization of a Manufacturing Seam Defect in High Frequency Electric Resistance Welded Pipe,” Proceedings of The 29th International Pipeline Pigging & Integrity Management Conference, Houston, TX, February 27 – March 2, 2017.