Abstract: To assess the safety of penstock in a small power station where some segments of penstock are defective with incomplete longitudinal weld, we built the finite element model of the penstock segment which contains such defects using ANSYS Workbench to solve the circumferential stress of penstock wall, and to determine the critical stress intensity factor of 16Mn steel. Furthermore, we built the finite element meshes of fractures in accordance with the weld’s defect characteristics and calculated the type I stress intensity factor at the tip of defect. Finally, according to the criterion of critical stress intensity factor, we concluded that the weld defects had no impact on the penstock safety, and did not expand in subsequent inspections.

Key words: penstock, safety evaluation, weld defect, ANSYS, finite element, stress intensity factor