Verification of piping calculations under blowdown loading by means of strain measurements

During blowdown tests with a feedwater check valve at the HDR-plant strains were measured at several cross-sections of a pipe. The strain measurements showed the oscillations of the pipe but also cross-section deformations in and near elbows. To evaluate those deformations a highly optimized Finite-Element calculation of the blowdown test at the pipe was performed; the theoretical stress- and strain-results without cross-section deformation were compared with values from the measurements, the differences showed the deformations. Furtheron in two elbows the ASME-values of cross-section deformation were theoretically calculated and showed mostly a good agreement with the measurements. (orig.)