Hi Peter

Manufacturers can usually supply some form of table for guidance. It will contain information on throughput, speed, and power consumption per unit length. I recently went through this exercise and converted some of the table into graphs, which I have attached to show you the general form of the relationship. ■

Since that picture didn't appear to come through, I will try including a hyperlink.

Click here ■

Do an internet search on



Screw Conveyor 101

by Michael P. Forcade

It is an excellant book for design of screw conveyors.

Gary Blenkhorn ■

We found a formula in the literature stating:

correction factor for inclination compared with horizontal conveying (angle written in degrees) =

1 - ( angle of inclination / 50 )

with a minimum of 0,1 (45 degrees) and a maximum of 1,9 (45 degrees down).

We calculated a lot of screwconveyors with this formula, but pratice showed that the formula predicts a far lower capacity than real. Therefor I know the experimental graph mentioned in the above reply will be more realistic.

Instead of dividing by 50 in the formula we found, the formula would be according the graph of Mr. Peter Donecker

factor = 1 - (angle / 140)

We know that this efficiency/correctionfactor differs very much for each product.

Vertical or almost vertical screw conveyors (inclination app. 90 degrees) work on basis of centrifugal forces and there you have another calculation method.

Jur Lommerts

==================

Jansen & Heuning Bulk Handlingh Systems

The Netherlands

e-mail: jfl@jh.nl

www.jh.nl ■

Dear Peter

According to my experience the best literature is Book 350 prepared & published by CEMA.

The horsepower is a sum of : empty ,horizontal , vertical & feeder.

In chapter 7 (inclined & vertical screw conveyors) is a graph with

three lines showing the effect of incline on screw conveyor capacity :

-standard design is effective up to 25 deg.incline(preffered 15).

-modified design should be used between 20 to 70 degrees.That means:close clearance , increased speed , short pitch , tubular through and no hanger bearings. You may use one or more of A/M

recommendations depend on incline (which is very important).

-over 60 degrees incline vertical design will apply.

If you have any questions I will be glad to help

Sincerly

S.Bar ■

Sorry Peter, but the angle of inclination is important, as is the degree of loading, as the mode in which the material conveys depends on these. Briefly, screws work either by gravitational, dynamic or flood mode and these have completely different characteristics. These modes are described in my book, ‘Guide to the Design, Selection and Application of Screw Feeders’, published by the Institution of Mechanical Engineers.

The behaviour is also sensitive to the physical properties of the bulk material handled, particularly the contact friction on the face of the screw flight and the bulk shear strength in differing states of dilatation. Please treat any published table on inclined screw capacity with reserve and as a rough guide only. If the answer is important I would recommend the advice of a specialist, it is much cheaper than being wrong. ■