Abstract
Field experience on pipelines suggests that under the unique conditions of tie-in welding, a high-low offset at the inner pipe wall is related to an increased occurrence of latent root weld discontinuities such as cold cracking. Codes and standards offer conflicting and unclear guidelines regarding acceptance criteria for high-low offset. This study presents a numerical index to quantify the influence of non-ideal joint geometry on the latent discontinuity susceptibility of the root pass for circumferential pipeline welds. The index is based on the stress concentration at the root and the angular distortion associated with plastic strains produced during welding. This index relates geometric considerations such as pipe diameter, wall thickness, and the cross section of the root pass with welding procedure variables and the mechanical properties of the pipeline material. Although this study is meant for steel pipelines, the conclusions obtained are also applicable to other materials. The index presented is a contribution towards an objective criterion for acceptance of high-low offset during field welding, ranking the susceptibility to latent discontinuities as a function of variables available to practitioners during field welding.
