Effect of local wall thinning at crown on the collapse Moment of elbow

Local wall thinning due to flow accelerated corrosion is one of degradation mechanisms of carbon steel piping in nuclear power plant (NPP). Thus, the local wall thinning has regarded as a main concern of carbon steel piping system in terms of safety and operability of NPP. Recently, the integrity of piping components containing the local wall thinning has become more important in maintaining the reliability of nuclear piping system. A number of studies have been performed to develop the methodology for integrity evaluation of piping components with local wall thinning. However, the effect of local wall thinning on the integrity of pipe bends and elbows was not yet systematically investigated. Only, our previous study evaluated the effect of local wall thinning locating at intrados and extrados. In this study, thus, the collapse moment of elbow containing wall thinning at crown is evaluated under various thinning shapes and loadings using finite element analysis. It is compared with results of intrados or extrados wall thinning to investigate the effect of circumferential thinning location on the collapse behavior of wall thinned elbows