Products can be conveyed and elevated at the same time by mounting a screw conveyor at an incline. This is often desirable because it covers two operations with one piece of equipment therefore saving space and reducing downtime, maintenance cost, etc. A standard screw conveyor will often operate normally at angles up to 15º with only a small loss in capacity. Beyond that, adjustments and/or modifications are typically necessary. The design is a bit involved and these items should be taken into consideration:
- More horsepower is required for Inclined Screw Conveyors: This is due to both lifting the product and “reconveying” product that falls back.
- Hangers should be eliminated: They create a “dead flow” area that is emphasized with inclined conveyors. This often results in the use of longer screws which require their own design considerations.
Other modifications that Conveyor Eng. & Mfg. often applies based on the situation:
- Tighter clearance between the screw and trough: This is especially true with granular, free flowing products such as dry, refined sugar.
- Higher screw speed: This increases the product’s forward momentum and reduces fallback.
- Shorter pitch screw flighting: This improves the relative angle between the each flight and the conveyed product.
- Use of tubular trough or shrouds: Both act in the same way to surround the screw and prevent product from falling back over the top which tends to occur more as speed is increased.
There are many variables involved including product particle size & shape, moisture content, etc. so past experience is often crucial to designing an efficient Inclined Screw Conveyor.
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