It is a screw shaped conveyor, which passes through a tunnel or a tube. A screw conveyor is an Archimedean screw contained within a tube and turned by a motor so as to deliver material from one end of the conveyor to the e other. It is particularly suitable for the transport of granular materials such as plastic granules used in injection, moulding, and cereals grains. It may also be used to transport liquids. In industrial control applications the conveyor may be used as a rotary feeder or variable rate feeder to deliver a measured rate quantity of material into a process. It consists of a tube or U-shaped stationary trough through which a shaft-mounted helix revolves to push loose material forward in a horizontal or inclined direction. It is one of the most widely used conveyors in the processing industry. Many applications in agricultural and chemical processing water screw developed circa 250 BC by Archimedes.