Finite Element Modeling of Locally Thinned Short Radius Pipe Bends

Abstract

This paper addresses the finite element modelling, analysis, and qualification of Carbon Steel pipe bends with Local Tinned Areas (LTA) under internal pressure and dead weight loading. Detailed 3D solid finite element models are constructed to represent short radius pipe bends typically used in feeder piping of the Primary Heat Transport (PHT) system in CANDU nuclear reactors. Two in-plane end-to-end bends are considered with the local thinned area located close to the middle of the second bend. Measured thickness data is used to construct idealized axial and circumferential thickness profiles ensuring a lower bound on the wall thickness over the entire bends region. Linear elastic finite element analysis is performed using the general purpose finite element program ANSYS. The pipe bends are assessed following the ASME Code SEC III NB-3221 approach and Section XI Code Case N-597-2. The results presented illustrate the effectiveness of the detailed finite element analysis in qualifying wall thickness significantly below the pressure-based thickness in locally thinned pipe bends.