Hydraulic turbines lifetime in terms of fracture mechanics

Abstract

The correct estimate of the lifetime of hydraulic turbines is an important part of planning the maintenance, repair or replacement of equipment.A positive experience in hydraulic unit operation over many years has proved their reliability and the possibility of long-term trouble-free operation. But, the occurrence of accidents and equipment failures confirm the need for new lifetime assessment approaches for hydraulic turbines, taking into account modern scientific achievements and technical capabilities.Currently, there are no generally accepted or widely used methods for estimating individual hydro turbine lifetime under real operation conditions.The lifetime estimation algorithm presented in this paper is based on the application methods of fracture mechanics to the main assemblies of hydraulic turbines. It takes into account constructive and technological features, operational modes and external loads. An individual forecast of the development of hazardous defects is built on mathematical models describing the change in the technical condition of equipment under real operation. The presented lifetime estimation method takes into account the development of initial or operational defects (cracks). The critical crack length corresponds to the instant when the influence of high-frequency loads becomes decisive, in spite of having a small amplitude. The impact of such loads leads to the rapid destruction of the structure.The proposed approach is convenient for the engineering assessment of the allowable lifetime for hydraulic turbines, does not require long calculation procedures and has a relatively low cost. This allows for the building of correct long-term forecasts which help to timely carry out the necessary repair, replacement or modernization of equipment.