Effect of Girth Welding on Strain Capacity of X80 SAW Pipes

Application of API X80 grade line pipes has been promoted to reduce a construction cost of the pipeline. Assessment of the strain capacity of X80 submerged arc welded (SAW) pipe is required for strain-based design (SBD). Long distance gas pipelines are usually constructed using girth welded line pipes. In the assessment of the strain capacity, it is important to keep over-matching at girth welds. However, since strength variation exists in base metal and girth weld metal, the value of the matching ratio also changes. In this study, X80 SAW pipes produced by the UOE process were welded under slightly over-matching condition and full-scale pipe bending test of the girth welded pipe was performed to evaluate the effect of the matching ratio on the strain capacity.