Nondestructive classification of LF, HF, and HF-normalized electric-resistance-welded(ERW)longitudinal seams

摘要

A nondestructive assessment of electric-resistance-welded(ERW)seam types through in-situ inspection can provide valuable data for pipeline integrity programs.The durability of ERW seams is known to depend on pipe manufacturing practices that have evolved over decades.However, for pipelines that have incomplete or missing material test reports(MTRs), there is no method to accurately identify the seam type and quality without the destructive removal of a section of the pipe wall at the seam for laboratory examination.This work presents a new methodology to accurately and nondestructively identify low frequency(LF), high frequency(HF)and high frequency normalized(HFN)ERW seams.The approach combines multiple nondestructive evaluation(NDE)techniques including a characterization of the macro-etched heat-affected-zone(HAZ)and assessment of hardness variation across the seam obtained through Hardness, Strength, and Ductility(HSD)tests.These quantitative measurements are input into a classification model that is calibrated with an existing database of known ERW pipe joints to automatically classify the ERW seam type.Case studies on in-service ERW pipe joints from in-ditch assessments are also provided.Future work will extend this multi-variable model to include characteristics of the steel quality and grade to establish correlations with an index of seam toughness.