Research On Dents Assessment Of Long Distance Pipeline

Oil and gas play a significant role in the development of economy and innovation oftechnology. People use the long-distance pipeline to complete the transportation of oiland gas. Safe operation of the pipeline is the foundation to protect people’s lives.Roughly there are four types of pipeline defects. They are corrosion defects, mechanicaldamage defects, design defects and mixed material defects. Dent is one of the mainpipeline forms of mechanical damage. When the extent of dent is wide, the detector cannot work. It is means that the pipeline will not be able to continue working. We need torepair of remove the pipeline. Some dents do not cause immediate of failure, however onthe one hand the presence of dents affect the carrying capacity of the pipeline, on theother hand the dents may cause cracks in the role of operate pressure, which can causefatigue failure. The existence of dents is a serious threat to the safe operation of the longdistance pipeline.The main topic of the research is residual strength evaluation of dented pipeline. Inorder to improve the accuracy of the residual strength, the thesis studied the detectionmeans of dented pipeline. The thesis mainly studies the residual strength evaluation andfatigue evaluation for different type of dents. Based on guidelines, the thesis proposes theevaluation process of dented pipeline. Moreover, from the mechanical properties ofmaterial and failure criteria, the thesis finishes the nonlinear finite element analysis byusing the ANSYS simulation software, and simulates the process of the formation andredounding. The thesis also analyzes the influence of the formation. To achieve anaccurate assessment of the dented pipeline, the thesis analyzes the von mises stress ofdents in the condition of different depths. To improve the efficiency of pipelineevaluation, the thesis uses the Matlab software to achieve the programming of theresidual strength,Research showed that the pipeline form a dent by creating plastically deform.Though the analysis of von mises stress, the stress at the edge of dents is higher the stress on the centre of dent., which also means the edge of dents has a high risk for the pipelinerunning. In the formation of dents in the pipeline, the depth of dents and external loadhas a proportional relationship, the depth and operate pressure has a inverselyproportional relationship, the depth and the thickness of pipeline has a inverselyproportional relationship. For different depths of dents, the pipeline has different carryingcapacity. For the pipeline, when the depth is less than the specify range the pipeline canoperate in the initial pressure, when the depth exceeds the range, the pipeline’s carryingcapacity of the pipeline decline.