Research On The Structure Of Reel-Lay System And The Safety Of Submarine Pipeline

Reel-lay is a new type of submarine pipeline laying method which developed from the traditional S-lay and J-lay laying technology.It is the core equipment for submarine pipeline laying using the Reel-lay.At present,the design and manufacturing process of Reel-lay laying equipment have long been monopolized by developed countries.The research on reeled pipe laying in China is still in infancy.With the gradual advancement of the strategy of Chinese marine power,the development of marine oil and gas resources will inevitably go to the deep sea,master the key technology of Reel-lay,break the technological monopoly of developed countries in this field,and realize the independent research and production of Reel-lay laying system,It has important theoretical significance and practical value for ensuring Chinese energy security and marine strategy.In this paper,by taking the rigid and flexible pipes suitable for Reel-lay as the research object,the process and technical requirements of the reeled pipe laying are studied,the limit state of the pipe and the failure mechanism of the pipe during the Reel-lay process are analyzed,and a pipeline failure mechanism is proposed.The failure criteria based on multiple judgments ensure the safety of the pipeline during the laying process of the Reel-lay.The core component structure and modular design method of the Reel-lay laying system were studied,and a Reellay laying system suitable for two types of pipelines and the corresponding laying scheme were proposed,which made more effective use of the internal space of the vessel and improved the laying system.Integration and reliability.Aiming at the safety problem of rigid pipes in the process of reeling and straightening,a theoretical simplified bending moment variation equation is established in which the pipe section enters the elastic-plastic process.Analyze the energy conversion relationship of the pipeline,and establish the straightening curvature equation of the pipeline according to the conversion relationship.Based on the nonlinear ring theory,the axial and circumferential strain equations of the pipe section during the reeling and straightening process are established,the Ramberg-Osgood constitutive equation model is used to establish the stress equation of the pipe-section.The mechanical equilibrium equation of the pipeline bending process is established by using the principle of virtual work,and the equilibrium equation is solved by the Newton iteration method.The change of the ovality of the pipeline-section with the curvature is obtained,and the influence of factors such as diameter-to-thickness ratio,yield strength and elastic modulus on the pipeline response is studied.Eventually,the theoretical analysis is verified by the combination of finite element simulation and land test.Aiming at the particularity of the working conditions of the Reel-lay operation,a dynamic coupling analysis model of the Reel-lay operation process including marine environmental loads,pipeline dynamics model and vessel motion factors is established.Analyze the marine environment of the four-level sea condition,and establish the calculation model of wind load,current load and wave load.Based on the vessel time-domain hydrodynamics theory,the motion response parameters of "HYSY 201" in the ocean environment are analyzed.The natural catenary theory combined with Morrison equation is used to determine the shape of the pipeline during the laying process and establish the mechanical model of each section of the pipeline.Taking the 10-inch standard flexible pipeline as the research object,the coupled model is solved by the New Mark-β method,and the dynamic response results of the axial tension,bending moment and stress-strain of the pipeline during the laying process of the Reel-lay under the fourth sea state are analyzed.Study the effects of rigid-flex pipelines,laying water depth,laying angle and marine environment on the dynamic response of pipelines.Aiming at the particularity of the working conditions of the Reel-lay operation,a dynamic coupling analysis model of the Reel-lay operation process including marine environmental loads,pipeline dynamics model and vessel motion factors is established.Analyze the marine environment of the four-level sea condition,and establish the calculation model of wind load,current load and wave load.Based on the vessel time-domain hydrodynamics theory,the motion response parameters of "HYSY 201" in the marine environment are analyzed.The natural catenary theory combined with Morrison equation is used to determine the shape of the pipeline during the laying process and establish the mechanical model of each section of the pipeline.Taking the 10-inch standard flexible pipeline as the research object,the coupled model is solved by the New Mark-β method,and the dynamic response results of the axial tension,bending moment and stress-strain of the pipeline during the laying process of the Reel-lay under the fourth sea state are analyzed.Study the effects of rigid-flex pipelines,laying water depth,laying angle and marine environment on the dynamic response of pipelines.Based on the design of the Reel-lay laying system,a full-scale rigid pipe Reel-lay test study and a scaling test study of a flexible pipe laying tower system are carried out.The Reellay laying test of full-scale rigid pipelines takes 6-inch pipes as the laying object.The pipe reeling and straightening laying tests are carried out in Tianjin Wharf and the Bohai Sea.The research on the laying scheme of the Reel-lay laying system proposed in this paper and the design of core components are carried out.It is verified with the theoretical analysis of the reeling and straightening process.Based on the principle of scaling,a scale model is designed for the tower structure of the flexible pipe laying tower system,and the angle adjustment test of the tower and the load loading test under normal working conditions are carried out,and the strain changes of key nodes are compared with the theoretical results to verify the safety and rationality of the tower structure design.