In several industrial sectors, the need for conveying fine-grained or small-sized bulk material with sealed machines, generally over small distances, can be satisfied by the various types of screw conveyors. Horizontal screw conveyors are generally used for powdered materials or small-sized material to be conveyed horizontally or with slight inclination (which may however reach 45° or more) whereas vertical screw conveyors are used for vertically lifting fine-grained material (also popularly known as screw elevators). When specially adjusted, horizontal screw conveyors may also be used to extract material from hoppers or silos. Special screw conveyors may be required to perform certain functions that include mixing, humidification and cooling, while other functions may be satisfied case-by-case through custom-made design solutions