After entering the machine, the classifying air flows through the classifying wheel in centripetal direction. In the process, the classifying wheel extracts the fines from the feed material and conveys them to the fines discharge. The coarse material rejected by the classifying wheel gravitates downwards. The air routing shown in the schematic is much simplified, because before the coarse material exits the classifier, it is rinsed again intensively by air to remove the remaining fines. This results in an extremely clean coarse fraction.
The product is fed either via a rotary valve or in the case of an air-flow classifier, entrained in the classifying air. Product fineness is controlled by adjustment of the classifier wheel speed using a frequency converter. The horizontal arrangement of the classifying wheel means that even "difficult" products can be processed with no problem.