The ultimate bearing capacity of defects in X80 pipeline steel

As the current assessment criteria and methods for residual intensity of pipelines with volumetric defects are mainly based on X70 pipeline steel and the grades below it, and the verification tests on X80 pipeline steel and the grades above it are rarely conducted. Based on this, the ultimate loading assessment models for the defects in various pipeline steels and their application ranges were firstly compared. And then, various defects of different sizes were prepared in X80 pipe for hydrostatic burst tests to evaluate the applicability of various assessment models in X80 pipe. It is shown that among all defects, the long rectangular defect is usually the lowest in bearing capacity, and the safe degrees of different defect prediction models are different from each other. As for the rectangular defect, the prediction result of DNV model is the best accordant with the experimental value, and the calculation results of ASME B31G Modified, RSTRENG and C-FER models are relatively safe. As for the groove defect, C-FER and PDAM models are applicable. And PDAM model is also suitable for the pit + groove defect.