Prototype Development Of Reel Lay System And Research On Pipe Mechanical Properties

Energy plays an important role in the human living and development.And,oil and natural gas occupies the main status of all the energy consumption.Because oil and gas resources on land are exhausted,the exploitation of marine oil and gas resources is imminent.During the development process,the offshore oil and gas resources need to be transported to land or ship.At present,countries around the world mainly adopt submarine pipeline for oil and gas transportation.Reel lay is a new pipe-laying method,which has the absolute advantages in the long distance and small diameter submarine pipeline laying.Therefore,the research on the key technology and the development on a reel lay system with independent intellectual property rights have important practical significance in breaking the foreign technology blockade and improving the level of marine engineering equipment technology.Firstly,the present development of submarine pipe laying methods is introduced,and the advantages and disadvantages in various methods are compared.For the reel lay method analyzed in this paper,the involved key theories are reviewed,including pipeline safety,pipe bending buckling theory and pipe straightening theory.In view of the technological characteristics of reel lay,the prototype overall scheme of reel lay system is put forward.Due to the assemble parts'big size and heavy weight,the modular design ideas are adopted.According to the functions and characteristics,the whole system is mainly divided into five parts including reel,aligner,straightening machine,tensioner,and laying tower.The structure and driving form of every part are designed.And on this basis,the schemes of hydraulic drive and control system are designed.In allusion to the high stress and easy-to-failure problem of pipe during reeling,a method of judging the pipeline safety is proposed.By analyzing the failure mechanism and force conditions of pipe during reel lay process,the ultimate load/strain bearing capacities are obtained.And the influence factors on the pipeline safety are studied.The pipe's safety in the experiment system is analyzed by this method,and the correctness of the reel design is verified.Pipe's buckling problem in reeling is researched.In basis of the nonlinear ring theory,the relation expression between the pipe cross section deformation and curvature is established.Considering the contact between pipe and reel,through the virtual work principle,the balance equation between pipe cross section deformation and external load is gotten.The balance equation can be solved by Newton-Raphson iteration method.The variation of pipe bending moment and ovality in reeling are obtained.The influence of geometric and material mechanics parameters and elastic springback on pipe buckling performance is analyzed.The on-land-test and simulation are used to verify the accuracy of this method.A model for continuous and rapid straightening is proposed for the problem that the pipe residual deflection is large after reeling.On the basis of the minimum potential energy principle,the maximum elastic pressure per unit length of pipe is obtained,and the relation between the pressure point and pivot of straightener and pipe mechanical performance is established.Based on the elastic-plastic theory,the mathematical relationship between residual curvature and straightening curvature is obtained by solving pipe bending moment and the ratio of plastic bending moment and maximum elastic bending moment.For a convenient operation of straightener in reel lay,the straightening reverse stroke and straightening stroke are further gotten.The influence of material and geometric parameters on straightening curvature is researched,and the straightening curvature formula can be simplified.Straightening process is simulated by ANSYS,whose results are compared with theoretical ones.The comparison shows that the theoretical value is smaller.An experimental study on pipe during reel lay is carried out.The experimental prototype is developed and the offshore test platform is built.And relevant experiments are carried out to verify the correctness of the theoretical calculation and structure scheme.The experimental results show that,the pipeline safety judgment method,the buckling analysis method,the pipe straightening model and theory and the structure scheme,are correct.The research results provide a theoretical basis for the engineering prototype of deep sea reel lay system and precious practical experience for practical operation,at the same time open the train of thought for the further research of submarine pipeline laying technology in China.It is of great significance.Believe in the near future,the reel lay system will play an important role in ocean development in our country.