Design And Sealing Analysis Of End Fitting For Thermoplastic Bonded Flexible Pipe

In the exploration and development of deep-water oil and gas resources,the research of thermoplastic bonded flexible pipe used in oil and gas pipelines has been paid more and more attention.Oil and gas pipelines are prone to damage and leakage because of the complex environment in deep water.The weakest link is the pipe end fitting.At present,there are no specific design specifications and mature products for thermoplastic bonded flexible pipe end fittings in China.The research of deep water thermoplastic bonded flexible pipe end fitting has great practical engineering significance and application value.In view of the defects of the existing thermoplastic bonded flexible pipe end fittings,such as the high requirement of installation preload,poor sealing and tensile effect,and being unable to adapt to deep water,this paper designs two kinds of marine riser end fittings suitable for ultra deep water.One kind of end fitting is mechanical sleeve end fitting,which provides the preload for installation and sealing by using the extrusion fit of cone and sleeve during installation.The sealing performance and tensile effect of the flexible pipe are realized by the interference of the taper serrated teeth and the end fitting mandrel serrated teeth on the inner and outer layers of the flexible pipe.The other type of end fitting is Wedge-Swaged end fitting,which provides the preload for installation and sealing by using flange to push wedge block to fit with the outer sleeve of end fitting during installation.The sealing performance and tensile effect is realized by the interference between the serrated teeth of the end fitting mandrel and the inner layer of the flexible pipe.In the form of sealing,the sealing effect is achieved by using the withholding interference contact between the serrated teeth of the end fitting mandrel and the inner layer of the thermoplastic bonded flexible pipe.ABAQUS is used to analyze analyze the connection effect of thermoplastic bonded flexible pipe and its end fitting,and the stress and strain of the end fitting and flexible pipe are obtained.The results were compared with the yield strength and elongation at break of each part of the end fitting and flexible pipe to judge whether the end fitting and flexible pipe failed.The contact pressure of the contact surface between the end fitting mandrel and the inner layer of the flexible pipe is obtained,and the results are compared with the minimum critical sealing pressure of the contact surface calculated by the fluid sealing criterion to judge the sealing performance.Furthermore,the influence of the interference between the serrated teeth of the end fitting mandrel and the inner layer of the flexible pipe on the sealing performance and bearing capacity of the deep-water flexible pipe end fitting is summarized.In this paper,the simulation results of two kinds of thermoplastic bonded flexible pipe end fittings in deep water meet the yield strength of the end fitting and flexible pipe,and meet the tensile and sealing properties of the end fitting.The influence of the interference between the serrated teeth of the end fitting mandrel and the inner layer of the flexible pipe on the sealing and tensile properties is obtained.According to the comparison of the optimal results of the two end fittings,it is concluded that the mechanical sleeve end fitting has better service effect in deep water environment.