Analysis and optimization of pipeline assembly and correcting based on finite element technology

During the pipeline assembly and correcting process, due to the not concentric pipes, excessive bend or torque, there will be residual stress left, which is latent process defects remained during the assembly process. This kind of defect will be quickly stimulated in use, causing the fracture of pipe and has the effect on reliability. Usually, in the practical engineering, many methods, including ageing heat treatment, temperature cycle test and natural ageing treatment, can be adopted to reduce or eliminate the defect remained in assembly process. This paper, based on the method of finite element simulation, conducts finite element analysis of different kinds of pipeline assembly and gives emergence mechanism and distribution of residual stress during all kinds of pipeline assembly process. Then according to the stress relax model of residual stress, some methods to eliminate the effect of residual stress are given and the finite element technique is applied to perform the ageing heat treatment simulation on corrected pipe, to analyze the variation of residual stress. Simulation results demonstrate the existence of residual stress defect during the pipeline assembly and correcting process and the elimination effect of ageing heat treatment on this defect. Furthermore, with the simulation results, according to different pipeline assembly and correcting situations different ageing heat treatment suggestions can be provided accordingly. The results also provide the foundation for the formulation of the ageing heat treatment scheme to eliminate the influence of residual stress.