Combined residual stresses and fluid-structure interaction finite element analysis on bent pipes

The combined inherent residual stress (RS) from manufacturing and in-service loading acted on a bent pipe which could be exerted from the fluid flow and/or thermal loading, a common situation faced by main steam pipes in high temperature plants, needs to be considered to understand their overall impact on the integrity of the pipe. The geometrical influence on a bent pipe’s stress distribution was investigated using a combined RS – Fluid-Structure Interaction (FSI) finite element analysis approach. The reduced stresses along the pipe derived from the room temperature RS-FSI simulation and analysis demonstrated the impact of the fluid and structure interaction, particularly at the locations where geometry varied. A substantial reduction in the stress level observed, especially at the extrados where wall thinning was detected. The combined RS-FSI analysis therefore offers a more realistic approach in predicting a safe allowable stress, thus the integrity or life of bent pipes.