A screw conveyor/feeder is the most economic transport means, since it is durable, and it implies minimal energy consumption rates.

Kinds of screw conveyors/feeders:

This equipment belong to three different categories:

• equipment defining the capacity, or extracting screw feeders: these are the ones which extract from a product column or door (e.g.: under the silos or hoppers).
• screw conveyors/feeders , here we are speaking of the machines which receive a load that has already been pre-defined upstream.
• reversible, extraction or screw conveyors, which, with several unloading outlets, and by inverting the sense of rotation, allow to discharge in several points.

Shapes of the screw conveyors/feeders:

These pieces of equipment differ according to how they are built:

• tubolar screw conveyors/feeders, where the jacket or trough of the carrying-spiral is a tube with a circular section, they are recommended for carrying products that are runny and not necessarily non-runny and hygroscopic.
• trough screw conveyors, where the trough where the spiral is encased is “U”-shaped, and the upper end is closed with a bolted or hinged lid, they are recommended for carrying non-runny products, ones requiring aeration or when it can be necessary to inspect the machine thoroughly, thus acting on the lid, they are also used for evacuation under industrial aspiration or dust-freeing filters .
• pipe-like/trough screw conveyors where a part of the trough is shaped like a groove and the remaining part is tubular, they are used when it is necessary to extract products, but it is not possible to make the part of the load too small when non-runny, hygroscopic products are used, or ones that create ‘bridges’.
• spiral-shaped screw conveyors/feeders lacking an inner shaft, where the spiral of the screw conveyor/feeder does not have an inner shaft and rests directly on the trough by sliding on it, they are recommended to carry muddy products or scrap or waste.
• screw conveyor/feeder bottoms, where one or more parallel spirals are encased in a single trough; they are used to evacuate non-runny, hygroscopic products, or ones whose size is considerable.
• batching screw feeders/conveyors and micro feed screws, they generally consist of 2, flanked or overlapping, spirals, and with different diameters. The spiral whose diameter is larger carries the largest part of the load until – when the batch or the weighing point is being approached – it stops and the spiral whose diameter is smaller carries out the finishing batching

All these pieces of equipment can be made of stainless steel or carbon steel and most of these can be certified in conformity with ATEX norms