## Investigation of Mill Balls Metal Deterioration in Mills KBM 370/850 (Sh-50А) when Fuel not Envisaged in the Mill Design is Used at Thermal Power Plants

Method for determining mill balls metal deterioration rate in a ball mill KBM 370/850 (Sh-50А) of dust-system of coal-dust boilers TPP-210А and TPP-312 300МW of thermal power plants is described in the paper. The research is aimed at the development of the determination method of the mill balls deterioration rate in a ball mill, which would allow predicting the regulated refill of the ball mill by the mill balls.