Screw conveyors are systems for transporting materials of small size in small amounts. They are used for powdery or liquid materials, guaranteeing quick transport with no spillage. They are usually positioned after the single-shaft grinders, transporting the material to the next treatment or discharging it in big bags. Built with an open conduit with covers for easy maintenance and cleaning, but also with tubes of different diameters to assure maximum tightness for the transport of lightweight materials such as granulated plastic, wood or rubber. Available in various lengths and diameters designed with perforated sections in predefined parts for controlled drainage.