The Screw Conveyor was invented in ancient Greece. It was originally used for lifting water. The credit for the invention is attributed to Archimedes. Even today, the basic design concept of the Conveyor Screw remains more or less the same except that power has replaced manual cranking to operate the equipment.
The mechanism of this relatively compact and efficient equipment is quite simple. The Conveyor Screw is fixed in a trough that usually rests horizontally on the floor on saddles and feet. A cover is placed over it. The other parts in the assembly include feed and discharge spouts, shrouds, flange, couplings, bearings and through ends. The only moving part is the screw. It picks up the material that is fed and conveys it to the other end as it rotates. Gates can be used to control the feeding and discharge.
These conveyors normally handle bulk dry materials. Since the trough is covered, dust contamination is not a real problem. The screws can be shafted or without shafts. They are available in different sizes. Normally they are used for straight line or slightly angled movement of materials. For certain applications, multiple screws are also used. The materials from which screws can be manufactured include steel, stainless steel, nylon and Teflon. Sometimes aluminum or brass is also used. Anti-corrosive treatments are normally given for steel screws. Since the screws are wear resistant, maintenance is minimal.
A more versatile version is the flexible Screw Conveyor, which is also referred to as a spiral conveyor. This is normally process-specific and has to be custom-made after taking into consideration various aspects of the operation for which it is used. It can convey materials horizontally, at different angles and even vertically.
Both fixed screw and flexible types are efficient, and simple to install and operate. The running costs are low. Cleaning is easy. They are almost maintenance-free. 5/16 inch to mm