Screw Conveyor

Screw conveyors can be classified into various types based on different criteria. They are categorized by conveying mechanism into shafted and shaftless screw conveyors; by structural shape into U-shaped and tubular screw conveyors; and by layout configuration into horizontal, inclined, and vertical screw conveyors. Each type differs in terms of structural characteristics, suitable materials, and application scenarios; therefore, proper selection is crucial for ensuring the equipment's long-term, stable operation. Since each type offers unique advantages and a specific scope of application, users should make an informed choice based on the characteristics of their materials and their specific process requirements.

Structural composition of the equipment

(I) Structural differences based on conveying mechanism:

Shafted screw conveyor: Consists of a screw shaft (auger) with a central core, a U-shaped trough (or cylindrical casing), a cover plate, inlet/outlet ports, and a drive unit. Helical flights are welded onto the screw shaft, which transmits torque via the central core. Suitable for non-sticky, dry powdery materials and small granules, such as cement, fly ash, lime, and grain.

Shaftless screw conveyor: Utilizes a shaftless screw (thick, ribbon-like flighting) instead of a shafted screw. Replaceable liners are installed within the U-shaped trough, resulting in a simpler structure. The entire conveying process can take place within a sealed trough. Suitable for conveying sticky or easily entangled materials, such as sludge, biomass, and waste.

(II) Structural differences based on external configuration:

U-shaped screw conveyor: Features an open U-shaped trough, with the option to install a top cover plate. This design facilitates the monitoring of material flow as well as cleaning and maintenance. Suitable for conveying general materials.

Tubular screw conveyor: The casing consists of flanged seamless steel pipes and is equipped with a labyrinth seal structure. It offers superior sealing performance, making it ideal for applications requiring strict leakage prevention. Available in carbon steel or stainless steel; the discharge end is equipped with a cleaning device.

Application scope of the equipment

Different types of screw conveyors have distinct application scopes:

Shafted screw conveyors: Primarily suitable for the horizontal or slightly inclined transport of non-sticky, dry powdery materials and small granules. They are widely used for conveying materials such as cement, fly ash, lime, and grain.

Shaftless screw conveyors: Primarily suitable for conveying sticky or easily entangled materials. They are widely used in environmental protection sectors such as sludge treatment, sewage treatment, biomass transport, and waste management.

Horizontal screw conveyors: Suitable for short-distance material transport in a horizontal position or at a low inclination angle (typically ≤20°).

Vertical screw conveyors: Suitable for the vertical lifting of materials, with conveying heights ranging from 2.5 to 15 meters.

Types of usable raw materials

Materials suitable for shafted screw conveyors: Cement, fly ash, lime, grain, cereals, compound fertilizer powder, dry powders, and other non-sticky, non-tangling powdery or small-particle materials.

Materials suitable for shaftless screw conveyors: Sludge, biomass, refuse, kitchen waste, sticky materials, materials prone to tangling (such as those containing fibers), etc.

The working principle of the equipment

Shafted screw conveyor: Rotating helical flights push the material along a U-shaped trough or a cylindrical casing. The material's own weight and the frictional resistance of the casing prevent it from rotating with the screw, causing it instead to move axially.

Shaftless screw conveyor: The shaftless screw body functions as the screw shaft, while the material acts as the nut; continuous rotation of the screw body results in continuous material transport.

Tubular screw conveyor: Material is propelled by helical flights within an enclosed cylindrical casing, with the head and tail bearings positioned outside the casing. Intermediate bearings are of the sliding type and are equipped with dust-proof sealing devices.

Equipment operating instructions

(1) Key points for operating the shafted screw conveyor: no-load start. Gradually increase the feeding speed to the rated conveying capacity. Feeding should be uniform to avoid clogging. Pay attention to check the temperature rise of the middle hanging bearing.

(2) Key points for operating the shaftless screw conveyor: During initial operation, the temperature of the motor and reduction box must be monitored during each operation. Unblock the ventilation hole of the motor reduction box to ensure smoothness. Check the nylon pad for wear.

Equipment maintenance methods

(I) Maintenance of shafted screw conveyors: Inject approximately 5 grams of lithium-based grease into the bearing housings at both ends every two weeks. Periodically lubricate the hanger bearings. Check the clearance between the screw flights and the casing to prevent rubbing.

(II) Maintenance of shaftless screw conveyors: Inspect the nylon liner after 6,000 hours of operation; replace it promptly if wear is excessive. Monitor the wear condition of the shaftless screw body.

(III) General maintenance: Lubricate the gear reducer in accordance with the instruction manual. Change the oil in the gear reducer after 2,000 hours of operation. Conduct daily inspections of the machine's operation and replenish bearing grease as necessary.