 Unbonded flexible pipe is widely used in the oil and gas industry for its good flexibility, especially in deep-water oil and gas production and transportation. And the nonmetal unbouded flexible pipe has excellent corrosion resistance and wear resistance. However, they are subject to internal pressure, external pressure and tension loads during the operation and service phases, which are important aspects affecting the integrity and security of the flexible pipe. In this paper, the mechanical behaviors of 8 inches nonmetal unbonded flexible pipe which consists of internal layer, internal pressure layer, anti-friction layer, carcass, tensile layer and external layer is investigated by numerical methods. The internal layer is high performance thermoplastic polymer material, the internal pressure layer and tensile layer is aramid fiber winding structure, and the carcass is high strength carbon fiber/resin composites. A rigorous three-dimensional solid finite element model of flexible pipe that considers the real material parameters, structural nonlinearity as well as the nonlinear contact behavior between components was created using ABAQUS. The material parameters of each functional layer were obtained by experiments. ABAQUS/Explicit quasi-static simulation is adopted to study the mechanical behaviors of the unbonded flexible pipe under combined load. And the accuracy of the simulation method for the internal pressure layer and tensile layer is verified by comparing with the small-scale internal pressure burst test of 1 inch flexible pipe. The mechanical behavior of flexible pipe subjected to internal pressure, external pressure and tension load was investigated in detail. The failure model and failure loads of flexible pipe were analyzed. Effects of the structure parameters such as the braided angle of aramid fiber braid layers, and the thickness of each layer were investigated. Based on the parametric study, some practical conclusions have been obtained which may be use for the practical      design and production of flexible pipe. This study can be referenced for the applications of nonmetal unbonded flexible pipe in marine oil and gas production.


Numerical Analysis of the Mechanical Behaviors of Nonmetal Unbonded Flexible Pipe Under Combined Load

Division / Sponsors: 
Pipeline Systems Division

Paper Proceedings: https://asmedigitalcollection.asme.org/IPC/IPC2020/volume/84447

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