A screw conveyor or auger conveyor is a mechanism that uses a rotating helical screw, called "flighting", that is installed within a tube or trough, to move liquid or granular materials. They are used in many bulk handling industries. Screw conveyors in modern industry are often used horizontally or at a slight incline as an efficient way to move semi-solid materials, including food waste, wood chips, aggregates, cereal grains, animal feed, boiler ash, meat and bone meal, municipal solid waste, and many others. The first type of screw conveyor was the Archimedes' screw, used since ancient times to pump irrigation water.
They usually consist of a trough or tube containing either a spiral blade coiled around a shaft, driven at one end and held at the other called a solid shaft screw. Other types are open helix or shaftless screws driven at one end and free at the other. The rate of volume transfer is proportional to the rotation rate of the shaft. In industrial control applications the device is often used as a variable rate feederby varying the rotation rate of the shaft to deliver a measured rate or quantity of material into a process.
When space allows, utilizing an inclined screw conveyor is a very economical method of elevating and conveying materials. As the angle of inclination increases, the capacity of a given unit rapidly decreases. The general rule of thumb is 45 degrees or less, otherwise the material will end up falling backwards over the flighting and not conveying to the intended destination.
VeloDyne Systems has manufactured screw conveyors for more than 10 years, in many applications conveying all types of materials from cheese, food powders, seasonings, pellets, flakes, and chips.