Study On Static Analysis Of Suspended Pressure Pipeline With Defects

Oil and gas pipelines have to cross the region with complex geological conditions, and the external loads can lead to large-span vacant on pipes. The suspending can cause stress concentration and large deformation in the pipeline. When a greater stress and strain and displacement occur on the pipe, the defects will exacerbate the tendency of failure of suspended pipelines, the pipeline will have a serious fracture failure, and that will threaten the safe operation of the pipeline. Therefore, it is necessary to study mechanical safety on suspended pipeline containing defects; the thesis is to provide direct theoretical support for Pipeline Company having rational and economic repairing job and make a foundation for the formulation and revision of appropriate evaluation criteria or guidelines.In this thesis first, I use big immunity beam theory, Winkler assumption and pipe-soil interaction bilinear model to establish the finite element theoretical model of the suspended pipeline containing unfitness and corrosion pits defects. Secend, according to ’GB50236-2011Code for construction of field equipment, industrial pipe welding engineering", to determine unfitness of butt joint in the standard; and using DNV RP-F101standard and PCORRC method for predicting failure pressure, to determine corrosion pit defect size of the oil&gas pipe in service according to actual working pressure in pipe. Then, combined with pipelines" data provided by the Western Pipeline, finite element simulation model of the suspended pipeline containing unfitness and corrosion pits defects is created correctly by ABAQUS. The last, models under the action of internal pressure have been the nonlinear analys, and failure behavior of suspended pipeline containing defects are discussed and studied.This paper identifies the failure criterion of large deformation suspended pipe containing defects, and through case studies, to verify the correctness of the failure criterion. Secondly, analyze Se-ning-lan’s suspended pipeline containing unfitness defects, and by contrasting the equivalent stress、strain and deflection obtained under different conditions. I found that when theunfitness defect in the pipe segment suspended pipe end, the unfitness of butt joint and the pipe wall thickness have a large amount of influence on the failure of the pipe. When the unfitness defect is located in middle of the suspended pipeline, it has small influence on the failure of the pipe.And give security and limit length of the suspended pipelines. Finally, analyze Xi-yi-line’s suspended pipeline containing corrosion defects, study failure location of suspended pipelines when contain corrosion pits and how the length, width and depth of the corrosion defects affect stress, strain and displacement of pipeline, and apply to a given failure criterion to determine the security and limit length of the suspended pipelines. The results obtained for the suspended pipe containing defects has actual evaluation guidance and provide direct theoretical data support for the pipeline company’s maintenance and repair jobs.