Flexible screw conveyors
Design for flexible screw conveyors
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| Page summary |
|---|
| 1. Introduction :
flexible screw conveyors |
| 2. Design of
flexible screw conveyors |
| 3. Comparison with
other bulk handling systems |
| 4. Cleaning and maintenance |
| 5. Flexible screw conveyors manufacturers |
1. Introduction : flexible screw conveyors
What is flexible screw conveyor ?
A flexible screw conveyor is a mechanical conveying system designed to transport bulk solid materials (powder, pellets, granulates...) within a factory. The transportation can be horizontal, inclined, or a combination of both with some bends.
Flexible screw conveyors are used for relatively small distance (5-10 m, sometimes up to 20 m).
2. Design of flexible screw conveyors
Flexible screw conveyors characteristics
As for a standard screw conveyor, the elements constituting a flexible conveyors are :
- Tube
- Screw flight
- Drive
- Bearings / Seals
- Inlet and outlet
The main differences are in the design of the tube and the screw flight. The tube is indeed made of plastic material, typically polyamide or special polyethylene, which allows it to be flexible and thus bent in a way that allows to arrange the conveying path according to the layout of the factory. The screw flight is made in steel and is shaftless which allows it to bend inside the tube. The drive is typically positioned at the outlet of the screw which allows to keep its seal and bearing away from the product.
Figure 1 : principle of a flexible
screw conveyor
It must be noted that the screw flight is in contact with the tube when there is no product in the pipe. When product is conveyed, it allows to fill the gap in between the screw flight and the tube and then center the screw flight thus avoiding or reducing the risks of contacts in between the tube and the screw flight.
Different designs exist for the screw flight "pig tail". The most common design is a round spiral while profiles with a flattened spiral exist also, the manufacturer being usually able to select the profile giving the best transport, from data acquired earlier or thanks to pilot plant trials.
Typical capabilities of flexible screw conveyors :
- Conveying distance : 5-10 m, up to 20 m
- Inclination : up to 60°
- Diameter : up to 90 mm, some special executions up to 200 mm
- Capacity : 7 m3/h, some special executions up to 40 m3/h
3. Comparison with other bulk handling systems
| Flexible Screw Conveyors | Pneumatic Conveyors | Belt Conveyors | Bucket Elevators | |
| Operating Principle | Positive displacement | Pressure or vacuum-driven air flow | Continuous motion with pulleys and belt | Continuous motion with buckets attached to a chain or belt |
| Design | Tube with flexible screw and shaftless screw flight | Pipeline system | Belt running on rollers supported by rollers | Buckets attached to chain or belt |
| Maintenance | Moderate | Moderate | Moderate to high | Moderate to high |
| Flexibility of Layout | Relatively
flexible, adaptable to various layouts and configurations,
limited in distance |
Highly flexible, the piping can be routed as per needed (be careful to pressure drop and breakage) | Limited by fixed path and curvature | Limited by fixed path and curvature |
| Material Handling Capacity | Moderate | Moderate to high | High | Moderate to high |
| Cost | Moderate | Moderate to high | Moderate to high | Moderate to high |
| Suitable Materials | Powders, granules, pellets, small granular materials | Powders, granules, pellets, granules | Bulk materials such as grains, ores, aggregates | Bulk materials such as grains, ores, aggregates |
| Environmental Impact | Minimal dust emission, relatively low noise | energy consumption dependent on compressor as well as design, technology (dilute or dense phase) | Dust emissions possible, energy consumption dependent on motor | Dust emissions possible, energy consumption dependent on motor |
4. Cleaning and maintenance
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How to clean a flexible screw conveyor ?
Flexible screw flights can be pulled out from the tube if the conveyor is short, although it is obviously more difficult when the length exceeds 3-5 m. It is however possible to drain a conveyor by dismantling the inlet (or opening a hatch that would have been designed to this effect) then slowly reverse the screw conveyor rotation. The material trapped is then pushed back to the inlet. This operation must be done careful as, like indicated in paragraph 2, without product helping to center the screw flight, a contact in between the screw flight and the tube is possible and could generate damages and foreign bodies.
In some cases the screw conveyor can be flushed with water or a cleaning liquid. Such as cleaning operation must however have been considered in the design to avoid long term damages such as corrosion of some parts.
How to maintain a flexible screw conveyor ?
Over time, it is possible that the plastic tube wears out because of the abrasion of the product or directly of the screw flight. It is then required to dismantle the flexible screw conveyor, extract the screw flight, then replace the tube by a new one.
Such an operation frequency can be reduced by using higher quality plastics and avoiding to rotate the screw when no product is conveyed.5. Flexible screw conveyors manufacturers
In order to get quotes, prices of flexible screws, the reader can refer to the following companies :
https://www.solufood.fr/transfert-dosage-poudres : flexible screw conveyors for sale(Note that PowderProcess.net has no link with those companies)