Calculation model for critical depth of kinked dents on pipelines with internal pressure

Abstract

Kinked dent is caused by the external force on the oil and gas pipeline, and its curvature is small, which seriously affects the operation safety of the pipeline. This paper focuses on the study of the critical depth of kinked dent for steel pipelines with internal pressure, to propose the safety evaluation criterion for pipelines with kinked dents. First, a full-scale hydraulic bursting test of a steel pipeline with kinked dents is designed, and the pressure-bearing capacity and the strain response law of the kinked dent in the test process are obtained. The results show that the pipeline does not fail at the kinked dent, and the kinked dent almost completely rebounds and has a certain pressure-bearing capacity. Then, a finite element simulation model of the pipeline with kinked dents is established, and the accuracy of the model is verified by comparing with the test. After that, the pressure-bearing failure mode and failure criterion of the pipeline with kinked dents are determined, the sensitive parameters affecting the failure are analyzed, and the effects of the parameters such as the depth and angle of the kinked dent, the diameter thickness ratio and yield ratio of the pipeline on the pressure-bearing capacity are obtained. Finally, based on many numerical simulation results, a calculation model for the critical depth is proposed as a safety evaluation criterion for the pressure-bearing failure of pipelines with kinked dents.