Vertical Mills use a double helix screw to stir the grinding media, which can be steel balls, ceramic media or pebbles. Feed enters the top of the mill and an external recycle pump provides an upward rise velocity in the grinding chamber. Grinding is by attrition and abrasion. Less energy is required when compared to conventional tumbling mills. The primary application for vertical mills has been regrinding base metal concentrates and for production of slaked lime.
Vertical motors are flange-mounted type motor. It is designed with enough starting torque to start the driver equipment under the specified starting conditions, and to produce the required horsepower rating to obtain the specified flow and pressure efficiently. Mechanically, the motor must be designed with special features that are unique to vertical motor applications.