Hi ljonline,

In West Australia we have gone for Mogensen Sizers. We have stripped out all our double deck screens, and replaced them with these units for sinter applications. They take up less space, and hopefully will prove to be more reliable.

Because they are an enclosed unit, they take far less air for dust extraction.

http://www.mogensen.se/eng/index.htm

Regards - Sgt John.rz

www.latviantourists.com.au ■

I have never heard that DESCRIPTION.......what does it supposedly mean please? ■

Hi George,

A Mogensen Sizer is basically a multiple deck vibrating screen with the decks set to a convex shape (something like an upside-down banana screen). It is called a "sizer" because that is a more generic term than "screen", which normally implies flat decks.

Check out the website for pictures and more details.

http://www.mogensen.se/eng/index.htm

Regards - John.rz ■

Hi John.rz: THANKS. I know what a MOGENSEN is....we have lots here.

I want to know what IJONLINE.......MEANS by the description equal thickness screens? ■

Thanks for your diagram.

This is what we call a differential deck design vibrating screen, deck slopes accomodate faster or slower FOOT travel PER MINUTE.......ON different sections of the screen surface. ■

Ijonline,

The differential deck design is also commonly known (in my neck of the woods any way) as the "Banana Screen", and can be used to advantage in applications that require large “through the screen” tonnages (lots fines much smaller than the mesh aperture), and they are better able to tolerate surge overloading. They are also better suited to handle materials with high surface moisture or inclusions of clay or mud, which are likely to cake the apertures.

To understand how a banana screen can achieve this increase in performance over conventional screens, it will be necessary to re examine some fundamental screening theory.

It is a well-known fact that the difficulty with which a particle can pass through an aperture is proportional to the ratio of particle size to aperture size. For example a particle that is 9/10ths the aperture size will have eighty times more difficulty in passing through the aperture than would a particle that is only 1/10th the aperture size.

During the screening procedure the particles that are near in size to the aperture will pass through the screen only if they arrive at the aperture in a favourable position. Consequently they are repeatedly represented to the mesh, and build up in a layer that remains on the screen while moving relatively slowly down the deck.

If the feed contains a high percentage of undersize particles capable of passing easily through the deck, it follows that their immediate passage will be obstructed (and screen capacity reduced) if they first have to work their way through a bed of material which if too thick will act as a continuous layer or type of filter.

The banana screen recognises the important effect of this layer and works on the principle that when the bed of material on the deck is kept relatively thin, the quantity of fines passing through the screen cloth per unit of time is very much greater than when screening with a thick bed.

To achieve this goal, the first part of the screen is arranged to start with a steep decline, which causes a flow rate with such high velocity that screening, is performed at a thin bed depth. This thin bed and high transportation speed is also quite tolerant to surges in the feed rate.

Furthermore the screen is operated with a large linear vibrating stroke which has the effect not only of further increasing the material velocity, but it tears the bed apart, opening it up and ensuring that particles move individually and freely to gain immediate access to the apertures. This includes the dispatch of moist fines that would cause blinding of the apertures if left longer on the deck. Likewise clay and mud remain loose and have the opportunity to quickly drop through the deck.

The flat portion of the deck at the discharge end then has a calming effect on the material, velocity is reduced and the difficult near size particle separation can occur unhindered by the fines.

Finally is should be understood that the banana screen is not a magic answer to all applications. Where the problems outlined above do not exist - conventional screens will do just as good a job for a much lower initial cost. ■

I have seen one screen placed one after another in one plan screening coke breaze in different sizes but they of same Thk SS plate. Are you talking of that?

Best regards, S K Banerjee ■