Design of Double Screw Hopper Conveyor

Michael Whytlaw
(not verified)

I am in the process of designing a double screw hopper conveyor and Incline Double Screw Conveyor.

Hopper Screw Conveyor.

-Length: 6m

-Volume Flow Rate: 12 cubic metres/hr

-Mass Density: Approx. 1000kg/m^3.

-Product: Bleached Earth (Earth/soil which is predominantly sticky, has a fair percentage of oil in it, bridges VERY easily even at 60-65 degrees of horizontal)

-It is a Hopper COnveyor. ie. It has has vertical walls 1.5m high on sides to allow product to "build up on screw" as it feeds it away. The product can't bridge because the vertical walls force the product to sit on the two screws.

-2 to 3 cubic meters of product can fall out in one go onto the screw conveyor in two locations in the hopper. (One at each end of the hopper)

-Proposed Screw Flight diameter: 450mm each.

-Screw flight thickness: 6mm Mild steel.

-Screw Shaft: 165mm O.D., wall thickness: 5mm

-Screw Speed: 6 RPM. (This will clear roughly 6 cubic metres every 10 minutes based on a 30% efficiency.


1. How do you calculate the power requirement.

2. Can I get away with no hanger bearings?

3. How do you calculate the power for the incline double screw conveyor (300mm Dia trough screw conveyor, 5000mm long)

Michael Whytlaw

Re: Design Of Double Screw Hopper Conveyor

Posted on 22. Mar. 2007 - 04:14

Look at CEMA publications for power calculations.

What is the angle of the incline screw, the higher the incline, the lower the efficiency, and as you go steeper you need to look at half pitch flighting.

You need to design to have no hanger bearings in the bin and on the incline. It means on a 6m long hopper you will have a very large centre pipe to limit deflection, or you will need to let the flighting run on longitudinal wear strips stitch welded into the bottom of the hopper.

In the hopper you will need to have a bottom shape similar to two flared troughs joined together so you don't get a dead zone between the screws where material can stay and harden or stick together and move en masse.

I have handled oil soaked soil as you describe in screws. Put in lots of inspection & clean out doors, and keep all chutes vertical. UHMW liners can also help.

Is this material all fines or any large lumps? That may also affect screw sizing.

Sorry for the rambling reply but you have a lot of variables to consider here.

Re: Design Of Double Screw Hopper Conveyor

Posted on 23. Mar. 2007 - 02:03

If the inclination is up to 30 degrees, I would go for a slick belt conveyor. The stikiness of the product will help it adhere to the belt and climbe up hill. Slick belt is easy to clean continuously by permanent blade scraper.