Ball mill
Metso's Mining and Construction Technology

Grinding of materials in a tumbling mill with the presence of metallic balls or other media dates back to the late 1800's. Since that time, Metso
and its predecessor companies, MPSI, Sala, Marcy, Hardinge, Kennedy Van Saun (KVS), Denver Equipment, Allis Chalmers, Boliden
Allis, and Dominion Engineering, have designed and manufactured more than 8,000 grinding mills.

Ball/pebble mills are suitable for:

* Ball mills for use of metallic media
* Pebble mills for use of ceramic or natural rock media
* Single stage fine grinding
* Regrinding
* Second stage in two stage grinding circuits

Main benefits of ball/pebble mills:

* More than 100 years of experience
* Automatic operation saves power
* Software to suit the most complicated circuits and complex ores

Main features of pebble/ball mills:

* Size range from 5 ft. x 8 ft. with 75 HP to 30 ft. x 41 ft. and as much as 30,000 HP
* Feed size is 80% passing 1/4" (6mm or finer) for hard ores and 80% passing 1" (25mm or finer) for soft ores
* Product size is typically 35 mesh or finer

Operation
Ball/pebble mills operate either in open or closed circuit. Open circuit operation is best utilized when:

* Another stage of grinding follows the mill
* Reduction ratio is small
* Feed material is already fine and one pass through the mill produces the desired results
* Product size control is not critical and oversize material can be tolerated in the product