Abrasion

The terms abrasion, wear and tear are of great importance when bulk materials are mixed or conveyed. Abrasion always occurs in the contact zone when two bodies move relative to one another. In this process, the harder body damages the surface of the softer solid.

Bulk material particles themselves should also be regarded as bodies. They generally have an irregular shape, as well as a minimum and maximum diameter. The finer the material, the greater the specific contact area and thus the potential for wear. Bulk materials can be classified, amongst other things, into microstructured particles in the range of 10⁻⁶ metres and nanostructured particles in the range of 10⁻⁹ metres.

Abrasion increases when the coefficient of friction between the particles is high, the pressure rises, the surface is rough, or the difference in velocity increases. Increased friction due to heating can also exacerbate wear. Furthermore, viscous liquids or abrasive powders between the particles promote wear.

When mixing a bulk material with a rotating agitator, the drive torque is a measure of the internal friction of the bulk material. During the mixing or conveying process, the particles rub not only against each other, but also against the mixing tool and the wall of the mixing chamber. This is precisely where typical wear zones develop.