Analysis On The Defects And Safety Of Long Distance Natural Gas Pipeline

With the rapid development of oil and gas energy industry,oil and gas pipeline has developed to large diameter,super thin wall,high pressure direction,creation of pipeline defects are also growing,security problem has become the hidden trouble of the oil and gas pipeline operation.Studying pipeline defects and safety problems is of great significance for safe operation of pipeline.In this paper,west of a line of west-east gas defect in a period of buried gas pipeline in xinjiang as the research object,mainly studies the causes of pipe crack defects and impact factors of the natural gas buried pipeline crack propagation in service.And seeking appropriate safety assessment method for crack defects.In this paper,buried gas pipeline are analyzed in the reasons of the crack defects,mostly due to defects in the weld zone,so the cause of defect is mainly due to micro cracks in the process of welding.Focuses on research fatigue crack extension mechanism,and the influence on the fatigue crack expansion factors were analyzed,because the pipeline is under the ground,the impact of pipeline fatigue crack propagation factors mainly in pipeline pressure fluctuations,strata movement and seismic effects.And using the finite element software simulated under three kinds of earthquake intensity section of pipe displacement,analysis the influence of different intensity earthquake wave to the pipeline,provides the basis for the effect of earthquake load on the pipeline fatigue crack extension.At the same time,in order to provide the foundation for the analysis of the fatigue crack propagation process,using the finite element software simulated under three kinds of earthquake intensity section of pipe displacement,analysis the influence of different intensity earthquake wave to the pipeline,provides the basis for the effect of earthquake load on the pipeline fatigue crack extension,the stress situation of Buried Natural Gas Pipeline under the action of soil and earthquake is analyzed.Stress intensity factor calculation and crack tip mechanical analysis of buried pipeline crack by using finite element software.The crack propagation process was simulated by finite element software and crack analysis software,and the crack propagation law was analyzed,to seek the appropriate safety assessment method for the pipeline crack defects,and to evaluate the safety of the pipeline.Analysis of the fatigue crack life prediction of three methods: Based on Pairs formula of crack of pipeline residual life prediction,based on Manson coffin formula of the low cycle fatigue life prediction and based on damage mechanics model of low cycle fatigue life prediction.Fatigue crack propagation is mainly low cycle fatigue.In this paper,the fatigue life prediction of selection based on Manson-Coffin formula of low cycle fatigue life prediction method.