Abstract

Material Diagnostics in Water Turbines

Water turbines form a comparatively small group of technical objects in this country. This is al unfavourable situation for the reliability testing. On the assumption that the reliability is a function of the pafameters characterizing the destruction processes in water turbines the reliability of the object can be evaluated indirectly. This requires establishing critical parameter values at which the reliability of the object is R_Ei=0. The principle of determining the reliability in this way is shown in Fig. 3.

In this manner the reliability and the time change of reliability of water turbines of 20 MW and 40 MW power were defined (period of three years' operation). A series scheme of reliability (Fig. 2) was adopted. It was recognized that the principal destruction processes over that period were the cavitation and cracking of elements of the flow part. Established were palameters which define the results of the processes (Eqs. (2), (3), (4) and critical values of the parameters (based on observations of the state of the turbine and on calculations - in the case of cracking of the elements (Eq. (8)). The change in the reliability of the turbines tested vs. time is presented in Fig. 13.