Screw Conveyors

A screw conveyor is a mechanical conveying system in which a helical screw rotates inside a tube or trough and moves material along its length. The rotating screw continuously advances the product from the inlet towards the discharge point, providing a compact and enclosed method of transfer.

Screw conveyors are commonly used for powders, granules and other free-flowing or semi-free-flowing bulk materials. Special designs can also be used for certain wet, semi-solid or difficult materials when the conveyor is engineered for that duty. The required configuration varies according to the product and the process.

Important selection factors include screw diameter, pitch and geometry, inlet and outlet arrangement, conveying length, inclination, rotational speed and drive power. These parameters determine how the conveyor handles the material and what capacity can be achieved.

Screw conveyors are used to transfer, feed and meter materials in a wide range of industrial processes. They can move products between storage, production and weighing equipment, feed material into mixers or processing machines, and deliver controlled quantities where dosing is required.

Typical conveyed materials include cement, coal, ash, mineral powders, marble powder, polyethylene and other plastics, flour, sugar, salt, coffee, spices and similar bulk products. Suitable conveyor construction must always be selected according to the characteristics of the material, especially where hygiene, abrasion, temperature or contamination control is important.

Depending on its design, a screw conveyor can function as a conveyor, feeder or dosing device. Capacity is influenced by the screw geometry, rotational speed, drive power, fill level and physical properties of the material being handled.

Tubular Screw: A rotating screw operates inside an enclosed tubular housing and moves the material from the inlet to the outlet. Tubular designs are widely used where an enclosed conveying path is required.

U/V Trough Screw: The screw rotates in a U- or V-shaped trough, typically manufactured from carbon steel or stainless steel. Trough construction provides access for inspection and maintenance and is suitable for many granular and powder materials.

Stainless Steel Screw: Stainless-steel construction is used where hygiene, corrosion resistance or product cleanliness is important, including applications in food, pharmaceutical and cosmetic processes.

Multi-Inlet Screw: Multiple inlets allow material to be collected from more than one feeding point and transported through a common conveyor.

Multi-Outlet Screw: A conveyor can be equipped with several discharge points, using slides or valves to direct material to selected locations or discharge points.

Dosing & Micro Dosing Screw: These conveyors are designed to regulate the amount of material being fed. Micro-dosing configurations are used where smaller and more precise feed quantities are required.

Cement Screw: Screw conveyors for cement-handling systems are commonly used beneath silos to transfer cement or similar dry construction materials to mixers, weighers or downstream process equipment.

Screw conveyors are used wherever bulk materials need to be moved, fed, distributed or dosed within a controlled process. Depending on the required construction and material compatibility, applications include:

They are also used in systems where enclosed transfer can help control dust, maintain product cleanliness or reduce exposure during material handling. The final design must be matched to the operating environment and the properties of the material being conveyed.

Screw conveyors offer several practical advantages when properly selected for the application:

Because the screw itself controls material movement, the same basic conveying principle can be adapted to a wide variety of capacities, layouts and material types.

Selecting a screw conveyor requires more than comparing purchase price. Price and overall price-performance are part of the decision, but they should be considered together with capacity, material characteristics and the operating conditions of the process.

Conveying capacity should be calculated before the equipment is selected. Screw diameter, speed, fill level, conveying length and inclination all influence throughput, while the bulk density and flow characteristics of the material affect the load on the conveyor and drive system.

Material compatibility is equally important. Food products, chemicals, abrasive minerals and construction materials may require different contact materials, sealing arrangements and surface finishes. Stainless steel may be appropriate where corrosion resistance or hygiene is required, while other applications may use carbon-steel construction.

Maintenance access, installation space, wear resistance and ease of assembly should also be considered. The most suitable screw conveyor is the one whose geometry, materials and drive system are matched to the specific duty rather than selected as a general-purpose solution.