Dear Shri Pradeep Rekhawar,

Your problem appears that you are getting screen material (passing material) which is containing some oversize material. If this is objectionable, you need to reduce the aperture size of screen deck. However, please note that, when you do so, screening capacity (capacity of screen passing material) will reduce, whereas more material will flow as oversize.

The aperture shape (square or round) is a separate issue. Both will not have the same dimension to derive identical product. There is an equivalent conversion between square and round aperture. For example, 25mm sq. opening is equivalent to 32mm round opening. 32mm sq. opening is equivalent to 50mm round opening. These figures are approximate.

Possibly, the round opening will have more blinding area on deck.

I suggest you to refer to the screen supplier to obtain their suggestion for your implementation purpose. Because altering the screen aperture size or the screen deck mass etc. might have side implications also. Hence, the problem should be tackled in totality.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

Hello:

The answer is yes you can.

Round HOLES:

- Give you a large hole than square holes

- Check WS TYLER screen handbook

- IE: Chart: Approx Round & Square opening Equivalents

For Testing Sieves

IF USING a 4" SQUARE GO TO 4 3/4" in ROUND

IF USING a 3" SQUARE GO TO 3 1/2" in ROUND

to achieve the same size passing one vs thee other....

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YOU DO NEED HEAVY MEDIA.....ie....PUNCHED PERF PLATE with and this is the key........1" X 2" longitudinal risers to keep really big rock.....from HAMMERING, abusing, and beating the holes out.

The skid rails will have the mega big stuff....slide right off top deck quickly.....and not make it down to the hole opening to cause havoc and lots of damage to the perf plate and the under lying support members of the machine.

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STAINLESS STEEL ........first, mega pricey, second not real swell for BANG CRASH PRIMARY SCALPING..... Thick rubber would be much better.......again with skid bars......

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SHOULD only be a ONE DECK SCALPER if a vibrating screen. Double deck brings zip all to a rough scalper application....except extra body weight and damage to the lower components.

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Really think a big EXTRA heavy duty BRUTE FORCE GRIZZLY FEEDER is the ticket here.......perfect for this application as long as we can fit the TOP SIZE IN.... LIKE a RIP RAP GRIZZLY FEEDER........portable or stationary.....FLEXIBLE adjustable GRIZZLY OPENINGS.......takes a lickin and keeps on tickin. 140mm to 160 mm bearing size range........HEAVY reinforced body.....oil lube.......

Hope this helps......a bit.

George Baker........MODERATOR ■

Dear Shri Pradeep Rekhawar,

Your problem with oversized material seems to be caused by the so called "fishes", which are passing the openings in vertical direction.

The reason is the grain shape of coke particals. If you make measurements on coke particle shapes in three directions you will discover that the third dimension is biger than the other two dimensions. You will have the same problem independent of aperture shape round or rectangular.

You should may be cheque your carbonization process and you coke crushers. ■

If you are in fact.........a particle shape problem.........IE.......elongates.......over 3 to 1 relationship.....an easy fix.......is to crush..........not with a compression type crusher.....but, do a test........on a VERTICAL shaft impactor.

This will IMPACT the coke.......not compress and split along grain lines. YOUR crushed product will now be CUBICAL or angular not elongated, carrots, slabby or arrows.

POSITIVE: nice cubical product screens and passes apertures much more easily than elongates.........and does not plug like elongates.

GEORGE B. ■

WE HAD ENCOUNTERED IDENTICAL PROBLEMS IN A INTEGRATED STEEL PLANT WITH COKE SCREENING, WHERE WE NEEDED - 24 MM UNDERSIZE. THE PROBLEM HAS BEEN LARGELY REDUCED BY USING TEAR DROP APERTURE. CONSIDERING THE SCREEN INCLINATION ETC WE SELECTED A HOLE STARTING WITH 13 MM DIA AND EXPANDING TO 25 MM DIA OVER A LENGTH OF 45 MM FROM THEIR RESPECTIVE CENTRES. THESE TEAR DROP DESIGN HAS REALLY WORKED AND MAY BE HELPFUL TO YOU ALSO.

YOU CAN CONTACT US WITH YOUR DETAILS ON amarj0411@yahoo.co.in. ALSO VISIT OUR WEBSITE www.torquo.com

AJMISHRA ■

You may consider trying these:

SELF CLEANING APERTURES, by this company:

http://www.majorwire.cc/

Call these folks and see the amazing results they have had on all material shapes and rectifying screening problems. ■

If you crush this material to a more CUBICAL Or ANGULAR shape then,

you screening dilema .......basically disappears.

A non elongated, carrot shaped, sliver-like, material shape will NOT cause problems passing openings.

So you can use square mesh and make a nice clean proper cut.

a plan B. ■

Dear everyone:

we can supply the perforated wire mesh.

website:http://www.forwardmesh.com

Cheers

Lisha

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