Burst Prediction of Flexible Pipes

Usually, when a large internal fluid pressure acts on the inner walls of flexible pipes, the carcass layer is not loaded as the first internal pressure resistance is given by the internal polymeric layer. The internal polymeric layer transmits almost all that loading to the metallic pressure resistant layer, or pressure armor layer. This layer must then be designed to ensure that the flexible pipe will not fail when loaded by a defined value of internal pressure. The present paper presents three different numerical models and one simple analytical model for determining the maximum internal pressure loading for a flexible pipe. The aim is to avoid pipe burst. The first numerical model is a ring approximation for the helically rolled pressure layer, considering its cross section as built. A second one is a full model for the same structure, considering the pressure layer laying angle and the cross section as built. The third numerical model is a 2D simplified version, considering the pressure layer as an equivalent ring. The first two numerical models consider contact nonlinearities and a nonlinear elastic-plastic material model for the pressure layer. The failure event and the corresponding stress state are discussed. Assumptions for each model are compared and discussed, with comparative results.