Collapse of Reinforced Thermoplastic Pipe (RTP) Under External Pressure

Abstract

Reinforced Thermoplastic Pipe (RTP) is a multi-layered thermoplastic pipe. It is increasingly used for transporting gas, oil and water etc. RTP pipe has many advantages compared with steel pipe, e.g. it is cheaper to produce, easier to install, more corrosion resistant and so on. Collapse under external pressure is often the governing design parameter for offshore pipelines. This paper presents the recent study result of RTP’s capacity under external pressure. Firstly, the calculation is carried out by mathematical analysis. In the mathematical analysis, RTP is assumed to be a 3-layered cylinder. The major factor that affects the collapse pressure is the flexural stiffness in hoop direction, so the reinforced layer (anisotropic) is simplified to be an isotropic layer with the same flexural stiffness as in hoop direction. The stiffness of this isotropic layer is the same with the RTP pipe. Secondly, Finite Element Analysis (FEA) method is employed to predict collapse pressure using ABAQUS. In the model the pipe is established as a 3-layered pipe with continuum shell element. The model is extended to take into account the initial imperfection and the plastic property of materials. Thirdly, to demonstrate the accuracy of the mathematical analysis and the FE model some test is carried out. This paper focuses on the calculation of RTP’s collapse pressure, using three approaches. The results from the three agree very well. The reasons for the deviations and the factors which influence the collapse pressure are discussed. The capacity equations and FEA models can be useful tools for design of RTP pipe.