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Flexible Screw Conveyors vs. Other Mechanical Conveyors

Posted on 6th October 2016 by

We have been setting up processors with flexible screw conveyors for more than four decades so our team is often asked about how these conveyors compare to other mechanical conveyors.

It’s common to hear flexible screw conveyors called different names. We’ve heard them all. If you call them auger screws, screw augers, flexible augers, screw conveyors, flex conveyors, helix or helical conveyors, flexible spiral conveyors, or spiral screw conveyors we’ll know what you’re talking about.

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Flexible Screw Conveyors: How They Compare

Flexible screw conveyors earn their name. These machines can convey material in any direction from horizontal to vertical. These conveyors can be routed around fixed objects and from room to room. They are often used to feed filling machinery, convey product from a hopper to a process, provide controlled feeding and dosing from bulk bags, feeding products from multiple inlets, loading silos or filling bulk bags.

Flexible Screw Conveyors: Benefits

Flex screw conveyors offer users a low cost, low maintenance, dust-free, and low-energy conveying solutions. These conveyors can have multiple inlets and outlets. Interestingly, screw conveyors offer the added benefit of constantly remixing blends. A spiral or screw rotates within a sealed tube. The speed and helical action of the screw makes the product in the conveyor rotate with the screw. The tumbling effect provides a homogeneous mix of particles in the conveyor, which is essential when feeding pre-mixed ingredients. Spiral speed is typically up to 1,150 RPM depending on the size of the conveyor and capacities are typically up to 29 ft3/min (0.82 m3/min). The conveying rate can vary.

Flexible Screw Conveyors: Materials Best Moved

  • Flexible Screw Conveyors are able to transport everything from fine powders to large pellets.
  • Material degradation is less than what might be expected compared to other mechanical conveyors.
  • Moist materials, sludge, and slurries are not suitable for flex screws.
  • They can transport hot and cold materials.

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Aero Mechanical Conveyors: How They Compare

The cable and disc assembly inside an aero mechanical conveyor moves at a high speed and the movement creates an air stream running at the same velocity. The material is fed into the airstream where it’s fluidized and conveyed to the outlet(s) where it’s centrifugally ejected. The entire system is dust-free.

Aero Mechanical Conveyors: Benefits

An aero mechanical conveyor has a high conveying capacity and provides total batch transfer. Like a flexible screw conveyor, an aero mechanical conveyor is a totally enclosed tubular system. The tubing provides a path for the driven cable and disc assembly to move around a circuit. These conveyors can operate at any angle with multiple inlets and outlets. They offer a reliable means of transporting material between processes and can be designed as mobile units. Aero mechanical conveyor speeds can reach up to 1,200 ft/min (366 m/min) with capacities typically up to 36 ft3/min (1 m3/min). They do not operate at variable conveying rates.

Aero Mechanical Conveyors: Materials Best Moved

  • The design of an aero mechanical conveyor allows the machine to convey a wide variety of materials.
  • Successful conveying of fragile, abrasive, hygroscopic, and fine particles are application dependent and we recommend material testing them first.
  • Hot material with temperatures over 300˚F (149˚C) and sludge-like materials are not recommended for these conveyors.

Tubular Drag Conveyors: Benefits

Tubular drag conveyors can operate with a chain and disc assembly or a cable and disc assembly. They are made of a sequence of straight and curved tubes that totally enclose the dust-tight system. This allows for gentle conveying of the material inside. It can operate in three planes, which eliminates transfer points. They can have multiple inlets and outlets. The conveyor only needs one drive. A cable drag conveyor’s speed is typically up to 140 ft/min (43 m/min) and its capacity is typically around 11 ft3/min (0.31m3/min). A chain drag conveyor’s speed is up to 100 ft/min (30 m/min) and its capacity is usually around 6.2 ft3/min (0.18 m3/min). Structural ultra heavy duty conveyors can reach speeds up to 50 ft/min (15 m/min). Variable conveying rates are possible.

Tubular Drag Conveyors: Materials Best Moved

Tubular drag conveyors are designed to move a variety of bulk materials. Depending on whether it’s a chain and disc assembly or a cable and disc assembly will affect what materials can be conveyed.

Non-structural Medium Duty Cable and Heavy Duty Chain Drag Conveyors:

  • Both chain and cable conveyors maintain blends. They also move dry and fragile products well.
  • Abrasive materials work best with chain drag conveyors but aren’t suitable for cable drag conveyors.
  • Hygroscopic materials should be avoided when using cable drag conveyors. They can work with chain conveyors, but we recommend running a test to be sure.
  • Moist materials work well with both types of conveyors, depending on the application. Chain drag conveyors tend to be more effective.

Structural Ultra Heavy Duty Chain Drag Conveyors:

  • Built within the confines of a pipe, this conveyor can handle pretty much any kind of material and temperature, up to 482˚F (250˚C).
  • Discs are made from a variety of materials including steel and cast iron. Other drag conveyors are typically made with UHMW discs.
  • The conveyors can work with slurry and fine particles, but a test is suggested.

Do I Need to Use a Test Lab?

I referenced testing a conveyor with your material a few times in this post but I haven’t mentioned how you do that. Here at Spiroflow, we have test labs in North America and in the UK. We highly recommend testing your product in your desired conveyor. This is the best way we can guarantee the final product. If you’re interested in a free consultation, let us know!

By the way, we don’t just manufacture conveyors. Click here to see our entire line of products. We also perform control systems integration. For more information on that, click here.

(1) 704-246-0900 | sales@spiroflow.com | +44 (0) 1200 422525

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Deron Seibert

Director of Sales at Spiroflow Systems, Inc
Deron has more than 20 years in the bulk material handling industry and has been with Spiroflow for more than 10 years. He has been instrumental in the execution of many of Spiroflow’s largest and most complex projects.