Trough Shape for Screw Feeder

1. Carry out pilot trials on smaller equipment, then scale-up.
2. Obtain advice from a number of proposed equipment suppliers.

An air lift would be the best but an archimedies in a tube should be ok. You need to watch for bridging at the delivery point.

If it was me I would go with the U shape. Its easier for inspection covers to mount etc etc. If the screw is a large one you will be changing hanger bearings down the road or segments of the screw. The U shape is maintenance friendly.

Apparently I wasn't logged in when I posted that last reply, new here..oops. But as I mentioned the U shape, what diameter of trough are you thinking ?

U shape I think for a simple powder like Zinc oxide would be over engineered - depends upon the length. But a u-tube needs a lid a tube does not and with an Archimedes screw there should be no problem. Air lift - depending on how far it has to go I still think is the best. Zinc oxide, unless contaminated, is a fairly free flowing powder.

I can only reply from work experience in uranium processing at two different sites. We used many screw feeders and all were round. The drives were remote controlled variable speed units with chain drives. There was a shear pin sensor in the form of a small generator on the tail end of each screw which would give an indication in the control room if we had a sheared drive pin. We did have to pull the screws when ever we had a jammed screw usually in the form of loose hardware getting in the process somehow. This required fume and powder vacuum as well as personnel safety equipment. Each screw barrel had a small sampling port on the bottom of the barrel in the form of a short nipple and valve. I don't recall many such screws being over four or five feet long. Chain link conveyors were used for long hauls both vertical and horizontal. They were in rectangular enclosures with removable cover plates and were very noisy.

The trough is very common because it makes it easier to access the flighting to work on it or pick out trash or whatever. It is commonly used for basic transmission of product.

If you have a lot of force on the powder in the feeder bin (an example of this is a tall bin with easily flow-able powder) then the material may overfeed by flowing over the top of the auger in the trough. In a situation like this you either add a choke to the trough or go with a circular housing with minimum clearance. Circular housings are often used when you are trying to meter powder. To consistently meter you must maintain a consistent "fill percentage" of the auger.

If you are force feeding the auger (with a packer auger or something else) you have to use a circular housing for above reasons. Also inclined augers at steep angles need circular housings to prevent fall-back.

thank you!