After the crushing process, rock and ores, coal and clinker are ground to fine grains or dust in mills. Vertical roller mills (also referred to as bowl mill crushers) have been used for many years to grind limestone for cement production and coal for heating and power stations, to name just a few examples.
The material is ground between a driven, rotating plate with a vertical axis and rollers with differently shaped profiles positioned above it. The material is fed back into the process over and over until it has been reduced to the required grain size. The number, shape and arrangement of the rollers vary, depending on manufacturer and specific task.
To compensate for the large angular movements, the grinding roller is guided in spherical roller bearings with an extended outer ring. These bearings are designed for rough operating conditions with heavy shocks and vibrations.