Why Sorting of the Balls?

As the time goes by, the distribution/proportion of the grinding ball sizes inside the ball mill gets changed, as a natural outcome of wear phenomena and/or breakage of the balls. Therefore the grinding efficiency drops. Every ball mill has a unique process result due to its physical condition, size, circuit, ground material, finish product type and auxiliary equipment. There is, however, a global thumb-rule for every ball mill that its best working condition is achieved by proper ball charge distribution determined by process experts (classification of 2nd chamber ball charge in 2 chamber mills is a good example of this fact). The importance and effect of proper ball charge distribution are proved by many lab tests as well as real industrial applications.
 

To sort the balls manually requires a big amount of time costing money and labor.

For example; 

A ball mil with 4,0 m diameter will have the following figures;

If the mill has 2 chambers: 

there are approximately 3,6 million balls available in the mill

If the mill is mono chamber  due to Roller Press: 

there are approximately 4,0 – 4,2 million balls available in the mill.

It is essential to keep the best pre-determined ball charge distribution inside the ball mill as much as possible for its efficiency.

For this purpose, generally, the recommendation is to sort 1st compartment ball charge once a year and 2nd compartment ball charge every 2 years.