Abstract

A flexible pipe riser is a flowline to oil transport from a subsea well to a floating unit, and it is composed of layers between these a carcass, a pressure sheath, a pressure vault, tensile armors, and anti-wear layers. A carcass or interlocked carcass is more internal layer and is projected to support radial forces. High radial forces can produce a collapse failure of an interlocked carcass. The interlocked carcass has a helical section geometry, so the pitch provides an interlock between its surfaces. These interactions between surfaces using a finite element model with an implicit method produce high non-linearity of the numerical problem for convergence of results. Therefore, a numerical model is proposed using a dynamic model with a quasi-static behavior and explicit solve method for the collapse analysis of an interlocked carcass. Numerical analysis is carried out in two steps. In the first step, the carcass pipe is generated by an angle of revolution applied to the section considering the pitch of the spiral. Therefore, a numerical model is developed to insert an imperfection in the perfect pipe. In the second step, an external vessel with stoppers is modeled where the carcass pipe is positioned internally, thus representing the pressure test with a hyperbaric chamber.

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