### The critical speed of the ball mill is less than 45

Chemical Engineering questions and answers. The critical speed of the ball mill is less than 45% of operating speed.Fote Mining Machinery Co. Now calculate the operating speed of the ball mill which has diameter of 900 mm. Diameter of ball is 80 mm. a) 47 rpm b) 68 rpm c) 32 rpm d) 21 pm. Question: The critical speed of the ball mill is less than 45% of operating speed.