As the ball wear rate depends directly on the surface of the media charge, a small variation in power will lead to an important increase of wear rate. The risk of underloading or overloading the mill is an additional factor. A direct measurement of the ball level in the mill, more accurate than power readings, as well as a control of it, is

We can calculate the steel charge volume of a ball or rod mill and express it as the % of the volume within the liners that is filled with grinding media. While the mill is stopped, the charge volume can be gotten by measuring the diameter inside the liners and the distance from the top of the charge to the top of the mill.