Abstract
Lifetime, functionality and efficiency of hydro turbines are dependent on the operating conditions and material properties such as fatigue strength, influenced by factors like water quality and occurring corrosion damage. Nowadays, Francis runners have to deal with various operating conditions outside the traditional operating range due to the demand of increased flexibility. Hence, it is fundamental that the Francis runner material features a sufficient fatigue life, since various amplitudes combined with different numbers of cycles occur. Worldwide, hydro power plant runners are facing different water qualities depending on the respective power plant location. Since chemistry of the surrounding potentially corrosive water has a decisive influence on occurring corrosion effects, different water qualities were defined to perform low-cycle and high-cycle fatigue tests under the influence of a corrosive medium. In hydro power stations, also acting as power reserve, longer standstill times can possibly occur and the runner may still be submerged in water. Therefore, investigations for idle-time corrosion were performed. In order to identify corrosion critical chemical elements and to evaluate the corrosion behavior of Francis runner materials, electrochemical polarization experiments were executed. For selected water qualities, preliminary material test results and microscopic analysis will be presented.
