Guide to Twin Screw Conveyors Types Uses and Selection

In industrial settings where materials ranging from wood chips and grains to viscous sludge require efficient, stable transportation, traditional conveying methods often prove inadequate. This is where twin screw conveyors demonstrate their value, becoming indispensable in modern production with their unique structure and robust functionality.

A twin screw conveyor is a mechanical device that utilizes two parallel, counter-rotating screw shafts for material transportation. Its core components include the drive unit, trough, frame, and screw flights, which may be constructed from carbon steel or stainless steel depending on application requirements.

The primary components include:

• Drive unit: Provides rotational power through motors and gear reducers
• Trough: Contains materials in U-shaped or tubular channels
• Frame: Structural support ensuring stable operation
• Screw flights: Core components that propel materials through rotation
• Inlet/outlet: Points for material entry and discharge

Materials enter through the inlet where counter-rotating screws (left-handed and right-handed) create axial movement through synchronized rotation. This design prevents clogging while providing mixing capabilities, particularly effective for non-homogeneous materials.

• Capacity: Up to 458 m³/hour
• Conveying distance: Maximum 60 meters
• Power range: 1.1-78 kW
• Screw diameter/flight pitch: Affects capacity and efficiency

Compared to single-screw conveyors, twin screw models offer:

• 1.5-2x greater efficiency
• Superior handling of low-flowability or bulky materials
• Compact footprint with easier maintenance
• Built-in mixing functionality
• Stable operation through counter-rotation

Structure: Flighting wraps around cylindrical housing without central shafts, preventing material wrapping.

Applications: Municipal waste, activated sludge, food waste, and other adhesive/tangling materials.

Pros: Excellent sealing, 1.5x capacity of single-screw models, multi-stage capability.

Limitations: Higher manufacturing cost, unsuitable for high-temperature or highly abrasive materials.

Structure: Central shafts support helical flights for stable operation.

Applications: Granular (grains, fertilizers), powdered (cement, lime), or small lump materials (coal, ores).

Pros: Heavy-duty construction, long-distance conveying, multi-point loading/unloading, 30% higher efficiency than single-screw models.

Limitations: Unsuitable for sticky or fibrous materials, requires more maintenance.

The counter-rotation of parallel screws creates axial material movement while preventing accumulation. The intermeshing action provides continuous mixing, making these conveyors ideal for heterogeneous materials like wood byproducts.

These systems employ two parallel (or intermeshing) screws that rotate synchronously or asynchronously to transport, mix, compress, or extrude materials. The dual-screw design generates greater thrust and mixing force than single-screw configurations, particularly effective for viscous, fibrous, or high-shear materials.

Twin screw conveyors excel in high-volume, continuous handling of bulk materials while often incorporating mixing, blending, or preliminary size reduction functions.

• Food processing: Grains, flour, sugar, byproducts
• Chemical: Fertilizers, dyes, plastics
• Construction materials: Cement, fly ash, mineral powders
• Metallurgy: Ores, slag, coke
• Environmental: Sludge, waste processing
• Feed production: Grain blending and transport

• Fertilizer plants transporting urea granules
• Cement plants blending raw materials
• Wastewater treatment facilities moving sludge
• Flour mills handling wheat and milled products

Choosing appropriate twin screw conveyors requires evaluating material properties, throughput requirements, conveying distance, and installation environment.

• Flow characteristics: Shafted models for free-flowing materials; shaftless for cohesive substances
• Adhesiveness: Shaftless designs prevent material buildup
• Fibrous nature: Shaftless configurations avoid wrapping issues
• Abrasiveness/Temperature: Material compatibility with flighting

Determine necessary throughput and conveying distance to select appropriate screw diameter, pitch, and potential multi-stage arrangements.

Evaluate space constraints, explosion-proof needs for flammable materials, and sanitary requirements for food/pharmaceutical applications.

• Cement/fly ash: Shafted conveyors with optimized flight geometry
• Sludge: Shaftless designs to prevent clogging
• Wood byproducts: Shaftless models avoid fiber wrapping
• Grains/fertilizers: Shafted conveyors with capacity-optimized screws

While twin screw conveyors focus on material transport, extruders emphasize mixing, plasticization, and chemical processing. Extruders serve more complex material transformation needs from laboratory to production scales, with selection depending on viscosity and processing requirements.

Twin screw conveyors deliver efficient, reliable material handling across diverse industries. Proper selection based on material characteristics, operational requirements, and environmental factors ensures optimal performance and productivity gains in bulk material processing operations.