In order to predict the erosion-threat over the stage, intensity and dispersion of the droplet streams must be evaluated. This may be done by taking advantage of numerous experimental data and estimating the intensity of the streams by use of experimental coefficients k₁, k₂, k₃ etc. Dispersion and intensity of the droplet streams along a nozzle channel may be also estimated.

Experimental data obtained in model wear research carried out with jets and special erosion devices may be used to determine the time-dependent mass losses of rotor blades. The formulae expressing the relative number of droplet blows of various dispersion are there necessary. These formulae have been derived on the basis of a normal distribution of wetness in various erosion streams. The results obtained from the formulae for determining the droplets number in the wide range of dispersion (from maximal droplets up to those of 5 pm in diameter) have been compared with the experimental data of the MEI (the Moscov Institute of Energy) and the KTZ (the Kaluga Turbine Works). The comparison showed a good agreement which confirms correctness of the theoretical assumptions.