Displacement And Stress Analysis Of Piping In A Below-to-above-ground Transition Area

Piping in a below-to-above-ground transition area whose stresses and displacements are studied in this work,is a common structural form for long-distance oil and gas pipeline.The structure includes: a buried pipeline segment that enters and exits the station,an aboveground pipeline segment connected to the buried pipeline segment,a pig trap and its piping.Under the temperature difference,internal pressure and soil restraint,piping will produce displacements and stresses,and there may be an insufficient strength for the piping.Displacement and stress analysis of pipings in below-to-above-ground transition areas are important to prevent excessive displacements and stresses of pipings for a long-distance pipeline station design.ABAQUS software and CAESAR II software are firstly introduced,and are compared from eight aspects,and their advantages,disadvantages and applicabilities are given: For nonlinear contact problems,it is more suitable to analyze with ABAQUS software.For the practical application of the project,it is more convenient to design stresses of pipelines with CAESAR II software.Then ABAQUS software is used to analyze the factors affecting the displacements and stresses of the pipeline.Distribution of stress and displacement in the pipeline is shown.It is considered that the temperature difference and internal pressure are the main causes of displacements and stresses of the pipeline.stresses and displacements of the “Z” type and straight laying pipelines are compared,and it is concluded that the “Z” pipeline laying mode is better than the straight laying mode in reducing the stresses and displacements of the pipeline..In view of the actual circumference of the displacements of pig receiver and launcher at the station in the Second West-East Gas Pipeline,CAESAR II software is used for stress and displacement calculation and check,and three kinds of buried compensation pipeline schemes are proposed: "Z","L ",and "?" type pipeline laying modes.Strength calculations of these three compensation schemes are carried out.The results show that all three schemes can reduce the stresses and displacements of the pipings,and the compensation schemes for buried pipelines are feasible.Finally,the position and shape of the three buried compensation pipeline schemes are designed,which provides reference for the design of pipings at below-to-above-ground transition areas in oil and gas long-distance pipeline stations.