A trommel is a screen that is curved into a cylinder. The machine spins the cylindrical screen in order to sort through the material as it is fed through. The tumbling action also allows maximum contact time with the screen so that the fine material gets through quickly.
Physical size separation is achieved as the feed material spirals down the rotating drum, where the undersized material smaller than the screen apertures passes through the screen, while the oversized material exits at the other end of the drum.
Trommel screen separates the waste stream effectively into different grit sizes and with this achieves a homogeneous mix of different wastes. The screening drums are available in various sizes with different-sized perforations, depending on the required throughput, material composition, application and purpose of screening.