This website will give you some details

http://youtube.com/watch?v=QOwgLWVgmV8&feature=related ■

Sorry for my earlier post. It was a mistake in pasting website. If possible I request moderator to remove my replay ■

This file gives details of one brand of Flip-Flow screen

http://www.tecprosystems.com/images/flipflow.pdf ■

A flip flop screen has a polyurethane deck that is allowed to flip flop (jump up and down) as material moves across it, thus preventing pegging and blinding of sticky material in a very particualr way.

Here is a video.

http://video.google.com/videoplay?do...42772334&hl=en

I just uploaded it so if it is not available yet, pls check back in a few... ■

Hello

There are several differences between conventional circular or linear motion screens and the Hein, Lehmann Liwell 'flip-flop' screen.

The Liwell screen has two screen cases to which crossbeams are attached alternately to each. Screen mats are attached to these crossbeams and then alternately flexed and relaxed 60 times per second. The mats are actually stretched beyond their original size. This changes the shape of the aperture (opening) which allows fines that may have accumulated in the corners to break their adhesion and fall through. This flexing also generates a great deal of energy. Conventional screens generate 5G of force but the Liwell generates over 50G of force. This creates a violent agitation which will knock a great deal of fines from the screened material thus cleaning material very effectively. This force also allows the screen mat to reject material that would usually remain wedged in the aperture due to inadequate force to knock the particle out.

http://heinlehmann.ca/liwell-principle.php

this link will take you to a short video that shows how the screen works. There are other videos on this site to show the screen working in limestone, coal and woodchips.

If you have any more specific questions I will be pleased to answer them for you. ■

Basically, what we usually say is when a conventional circle throw screen or even a horizontal or linear action screener fails....is unable to screen, plugs or does not handle the screening job efficiency wise..........then, go to PLAN B......which FLIP FLOP screen is one of a few alternatives.

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Basically, circle throw inclined depends on mother nature, gravity at 20 deg slope with an eccentric "LIFT" of the coarse material to

allow the fines to pass while the coarse if up in the air.

These units will typically run a 3/8" circle throw at 840-860rpm range for an operating G factor of about 3.5 g's. The concept here is we accelerate the whole body of the machine with the wirecloth, rubber or urethane attached to it at 3.50 to 4.0 g's.

Note: on a linear/horizontal screen gear driven the g factor is more like 6 g's range at zero degree install angle. We need more g's .......WHY?...because we do not have 20 degree angle of gravity to help us here....SO we need to do it all by motors combined with linear stroke LENGTH. Again, the wirecloth, rubber or urethane vibrates with the whole screen box together.

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When, we encounter materials that are HARD to screen, plugging, non-free flowing, lots of nearsize to openings in the wirecloth or urethane.....we need to try something different.

Hence the FLIP FLOP CONCEPT ........these units Liwell is one and BINDER or BIVITEC (USA) is another typical flip flop can be tested on the hard to screen material.

These units are typically dual vibrations modes.....with the shaft thru the body giving a 2g range of motion in a circle throw type of motion and the Urethane in the body actually moving in its own orbit or mode of vibration at up to 50 G's....accelerating force INDEPENDENT of the vibrating body motion. The urethane actually moves in a FLIP FLOP or SNAPPING type of action. Kinda like a piece of paper in your 2 hands.....extended quickly tight then, relaxed again. The key is the urethane material is kept CLEAR or NON BLINDED by this aggressive motion, AND efficiency is maintained typically where the wirecloth would be blinded on a conventional screening setup.

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Best way to ensure acceptability is to ask for a demo on YOUR actual material and prove or disprove It will work on your actual material. We have had super success on this theory in NICHE applications where nothing else would work. More expensive capital cost wise than conventional. Much quicker, easier to change out urethane than conventional.

Hoping this helps. Both Liwell and Bivitec are well known excellent companies to deal with. ■