Structural Study And Dynamic Analysis On Flexible Pipe-lay System

As the reserves of land oil and gas are decreasing,countries around the world begin to pay their interest to marine oil and gas resources.Pipeline transport is the major method of oil and gas transportation,pipe-laying technique and equipment have great significance for marine oil and gas gathering.As an advanced pipe-laying method,flex-lay can lay pipelines with faster speed,lower cost and higher security.Currently,there is a clear gap between our country and international advanced level in flex-lay.This task is aiming to make a structural design on overall plan and key structure of flex-lay system through looking into foreign mature flex-lay technology and equipment.By making structural design and dynamic analysis on flex-lay system,this task can lay a root for designing and building flex-lay systems with independent intellectual property rights.This paper firstly introduced characteristics and spheres of application of common pipelay methods by referring to worldwide technical literature,then made a summary on flex-lay research status in home and abroad.Workflow of flex-lay system and main parts including tensioner,A&R winch,angle adjuster,hang-off clamp are designed.Technic specs and detailed information of advanced marine flexible pipes are introduced.A catenary method of marine pipeline analysis was put forward,and key parameters like maximum tensioning force are calculated in catenary method.General structure of tensioner,angle adjuster,hang-off clamp and aligner are decided.An overall structure of flex-lay system is designed,and a set of 3D model is modeled using Unigraphices 10.0.According to the function and workflow of flex-lay system,key structures like pipe-lay tower,tensioner supporting frame,angle adjuster and hang-off clamp are designed,and their geometry sizes and force conditions are designed through theoretical calculation.Support equipments including aligner,centralizer and hatch block was designed.The flex-lay system was modeled and assembled using modeling software Unigraphics.The finite element software ANSYS was used to analyze the stress distribution and check the strength of the laying tower,hang-off clamp,tensioner supporting frame and angle adjuster.The simulation results confirm the reliability of the flex-lay system.Based on Kane equation and Lagrange multiplier method,the dynamics and motion equations of flex-lay system are established.Expression of driving force of the hydraulic cylinder during position adjustment process of tensioner and pipe-lay tower are obtained,and their relationship curves are calculated by pluging in mass and geometry parameters of the pipelay system.A feedback control system based on ADAMS and MATLAB is built to simulate these processes,and the results verify the correctness of the theoretical calculation.Combined with specific pipe-laying vessel and wave circumstances,swing statuses of the ship under degree 4 sea situation are calculated,and rolling,pitching and sway motion equations are put forward.A mechanical model and a wave load simulation platform are constructed in dynamic simulation software ADAMS,and a series of dynamic simulations on angle adjusting,tensioner moving,pipe-laying and pipe abandoning&recovering are carried out to obtain the maximum stress and curves of key nodes in the system.Results of these simulations can test and verify security of flex-lay system in rough sea situations.