Local buckling of subsea pipelines as a walking mitigation technique

Various factors influence the design of subsea pipeline subjected to high temperature and pressure operating loads. Cycles of operating shut-down and start-up have been shown to cause pipeline axial movement, which is called ‘walking’. Walking can influence pipeline performance and cause lateral deflection amplitudes at buckled zones as a result of walking and lateral buckling interaction. A novel cost-effective method for walking mitigation is investigated in this paper using of FE modeling to simulate the novel way of eliminating the occurrence of walking. The proposed technique for mitigating pipeline walking involves creating initial local lateral deformations along the pipeline via imposed local curvature during pipeline reel laying. The interaction between walking and lateral buckling is also explored for an example pipeline with initial local deformations imposed at regular small intervals along the pipeline. The effects of the residual curvatures on pipeline response to temperature and pressure loading are considered in this paper. The reduction in walking rate of subsea pipelines with different numbers of initial deformations is considered. Furthermore, a continuous snake-lay form of deformations is proposed as a very effective method for controlling walking and attaining virtually a zero value of incremental walking per cycle.