Impacts of pipeline steel upgrading on applicability of B31G standards

To determine impacts of extensive upgrading of pipeline steel to applicability of B31G standards, yield-tensile ratio, flow stress, defect depth ratio and other factors are studied systematically to highlight impacts of changes in yield-tensile ratio of the pipeline to value of flow stress. In addition, different editions of B31G standards are reviewed to clarify changes in conservative properties and centrality of calculation results obtained by using B31G standards induced by changes of defect depth ratio and upgrading of pipeline steel. The research results show that, with the increase of pipeline steel grades, the B31G calculation results become gradually less conservative, and tend to be aggressive. Moreover, the calculation results are much less centralized. In this circumstance, the B31G standards become less and less applicable to high-grade steel pipes. By redefining the value of flow stress, conservative properties of B31G calculation results can be enhanced to a certain extent, but it is difficult to fundamentally solve the problems related to applicability induced by low centrality.