On the Fatigue Reliability of Hydroelectric Francis Runners

The reliability assessment of large rotating structures like hydroelectric Francis runners is often limited by our capacity to define a proper limit state combined with a relevant degradation model. In this paper, we propose that the proper limit state for fatigue reliability of such structures is the onset of high cycle fatigue (HCF). Based on this premise, a prior interval for our limit state based on available literature is presented. The prior assumptions are believed to be the first step toward validation of the applicability and suitability of the proposed model. The paper includes an overview of the theoretical background for reliability assessment of Francis turbine runners, the methodology used, and the results obtained from the information gathered from the available literature.