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Flexible Screw Conveyors for Handling Bulk Materials in Canada

Flexible Screw Conveyors for Difficult-to-Handle Materials

Flexible screw conveyor systems are designed to transport bulk materials that are challenging to handle, including those prone to packing, caking, smearing, breaking apart, or fluidizing. They are also effective in preventing the separation of blended products.

Applications and Versatility
Flexible screw conveyors are suitable for handling most bulk materials, from sub-micron powders to large pellets, whether free-flowing or non-free-flowing. They can operate at any angle, navigate obstructions, and pass through confined spaces. With their simple design, compact footprint, reliability, and cost-effectiveness, they are an ideal choice for many industries.

This article focuses specifically on flexible screw conveyors and their suitability for materials that are difficult to convey, as alternate methods may sometimes be more appropriate depending on project requirements.

Engineering Considerations for Difficult Materials

Designing a flexible screw conveyor for challenging materials requires understanding key properties such as:

  • Physical characteristics (e.g., bulk density, particle size)
  • Flow properties (e.g., cohesive strength, angle of repose)
  • Temperature and moisture sensitivity
  • Allowable degradation and blending requirements
  • Conveying rate, distance, and layout

These conveyors are particularly effective for:

  • Cohesive materials
  • Ultra-fine particles
  • Fragile or friable materials
  • Abrasive substances
  • Materials prone to fluidizing
  • Blended products with varying particle sizes and densities

Critical Engineering Questions
To ensure optimal design and performance, engineers must consider:

  • Does the material pack, cake, or smear?
  • Is it free-flowing or non-free-flowing?
  • Does it absorb moisture or degrade in specific conditions?
  • Does it tend to fluidize, bridge, or dome?
  • Will blending integrity be maintained during conveying?

Material Testing
Material flow behavior under real-world conditions cannot always be predicted by laboratory tests alone. Simulating plant conditions with full-size equipment using the actual material is crucial for accurate performance assessment.

Flexible Screw Conveyor Design Features

Screw Geometry
The screw’s shape is critical to performance. Options include:

  • Round Screws: High radial forces, suitable for general use.
  • Flat Screws: Greater directional force, ideal for light, fluidizing powders.
  • Custom Variants: Beveled edges or heavy-duty designs tailored for specific materials.

Construction Materials
Screws are available in spring steel or stainless steel, while conveyor tubes may be made of stainless steel or polymer, depending on the application.

Integrated Systems
Flexible screw conveyors can be part of larger systems, incorporating:

  • Feed hoppers with flow promotion devices
  • Dust collection systems for fine materials
  • Weigh batching systems for precise control
  • Discharge equipment, such as bulk bag fillers

Flexible Screw

Challenges and Solutions

Cohesive Materials
These materials may bind, pack, or smear due to chemical reactions, moisture, or fat content. Proper hopper design with steep walls and flow aids, combined with a totally enclosed conveyor, can maintain product flow and protect against environmental effects.

Ultra-Fine Particles
Light, dusty, and fluidizing materials require screws with flat surfaces to minimize aeration and maintain control. Examples include fumed silica and diatomaceous earth, which benefit from specialized designs that prevent bridging and fluidization.

Fragile and Friable Materials
Flexible screw conveyors minimize breakage with their self-centering screw action, which prevents contact with tube walls.

Abrasive Materials
Durable screw designs, such as heavy-duty flat-wire screws, resist wear caused by abrasive substances.

Blended Products
Flexible screw conveyors maintain the integrity of blends, preventing separation during transport. For example, spice manufacturers use these systems to handle delicate and diverse mixtures without damage or segregation.

Conclusion

Flexible screw conveyors are an effective solution for handling a wide range of challenging bulk materials. Proper design, material testing, and expert engineering are essential to achieving reliable performance in real-world conditions.

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