Influence of loading regimes and operational environment on fatigue state of components of turbine and hydromechanical equipment at hydropower

Abstract

Horizontal Kaplan turbines, were installed in 10 generating sets units at „DJERDAP 2“. After 163.411 hours of operation, the fracture of the hydro-electric generating set A6 turbine shaft in the area of high stress concentration occurred, at the transition radius between the flange and the runner hub. In this paper the results of the analytical calculation regarding the strength of the turbine shaft are presented and influence of the corrosive environment, as well as tests regarding the fatigue. Tensile tests under constant amplitude loading were carried out on smooth specimens in order to determine fatigue properties of the base material, as well as bending tests on notched specimens in order to determine fracture mechanics parameters, or correlation between the crack growth rate da/dN and the stress intensity factor ΔK. It has been established that stress values were higher than allowable values, which led to the occurence of many cracks due to fatigue corrosion. One of those cracks caused the fracture.