Attention: Matt Reese

Before moving forward with changes in your screening system, you should review your sample collection methods and equipment to eliminate any errors that may exist in that area. As Francis Pitard describes in his book, "Sampling Theory and Samping Practice", (http://www.amazon.com/Sampling-Pract.../dp/0849389178), there are several different sources and causes for sampling errors. These include segregation error, extraction error, delimitation error and handling error. You may also be interested in viewing the sampling equipment offered by GRSEI, who offers a line of solids samplers that have no moving parts: www.GRSEI.com

Best regards,

Glenn R. Sprenger

303-525-9924 ■

Hello Matt: You gave me good info.......but, not the size of the screen.....but, for now........let's try these few points of interest.

First of all........a TYLER Tyrock.....the cadillac of screens...super unit. I worked those guys for about 10 years excellent equipment.

SOME OBSERVATIONS:

1. you are screening at nominal minus 1/4" opening. (plus minus 6mm) AND using a slotted opening in rubber

2. you are using slotted rubber mats VS wirecloth equates to lower open area available ...more chance to carryover fines

3. stroke at 3/8" is 860rpm and FIXED by the way on a TYROCK, non adjustable .

4. vsma BOOK states if using wirecloth as the media.....at 6mm or 1/4" opg you would have for a mid range wire diameter wirecloth nominal 46% open area available and theoretically should pass 1.60 stph per square foot .....just multiply your width x your length of deck x 1.60 and equates to theoretical TPH able to process........AND this assumes you are achieving +- 95% efficiency only.....which is what VSMA and most vibrating formulas in fact calculate for.

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COMMENTS RECOMMENDATIONS THOUGHTS:

1. 1% fines allowed or 99% efficient is HARD screening.....very tight efficiency. Note: wider screen or width = more TPH and length or longer = more efficient, more retention time to help get the fines out. You could have a length problem but, for now I doubt it.

2. SQUARE opgs if it will do the JOB always better to help keep product on SPEC. but, if slots will pass sieve test....better due to higher open area. By the way....the OA by vsma on wirecloth is 46% you are probably 25% OA on your rubber screen mats...equals more FINES carrying over...equals more likely to be off spec....harder to pass with less open area to do it.

3. SPEED & STROKE are definitely WRONG for this 6mm cut . If you check VSMA it is wrong setup. Should be more like 1/4" stroke at 1000 rpm. WHY??? wE want to throw the fines up in the air with the stroke less HIGH.....and we want to introduce the fines which must pass the aperture more times per minute (1000 vs 860 times) to increase probability of fines to pass that small opening.

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What probably happened here is you had a screen box......with 3/8" fixed stroke and speed......and put the fine rubber mat on and gave it a go......always happens. BUT, the machine is not setup properly here. What happens now is the 3/8" stroke is more suited for 1-2" screening and so the fines are stratified up in the air too much and carry over and or do not get taken out as they never get a chance to pass the 6mm hole.

ALSO IMPORTANT: the angle of installation should be minimum 20 degrees to achieve 95% efficiency up to 25 deg slope allowed on the high side by vsma. I think 20 should be fine.

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OPERATING G's: you are fine with your speed stroke for now, you do not want to go faster without TYLER permission, could snap the sideplates out. That 3/8 stroke is NOT adjustable because that is a DOUBLE ECCENTRIC offset tooled into that shaft.

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FINALLY: you are pretty close to your spec with the setup you actually are working with.......maybe you could use a couple of rubber curtains hanging across deck about 3/8" above the rubber mat to just slow the material down a bit, to increase retention time to try to make a tad more efficient.

GOOD LUCK.....hoping any of this helps. Keep Smiling

George Baker MODERATOR ■

see previous post........GB

Attachments

4 pg sizingformula vsma (JPG)

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Would you mind advising:

1. installation angle...........i assume 20 degree now

2. width and length and number of decks

thanks George.......curiosity. ■

mreese: Thanks for the reply, much appreciated.

To answer your questions:

1. No, I definitely do not agree with that recommendation at all

1600x5000mm (nom. 5'x16') 80 sq feet area. The 8 degree slope ....is a function of dealing with spheroids shapes (i assume) which will want to run past the openings. BUT, still disagree ....

2. We do not necessarily throw out the rule of thumbs of 20 degrees when talking round pellets. If what you have is only a 20 degree angle screen to do the job. .... We must think on our feet at this point. My review observed you are almost doing this job but, just slightly off on the efficiency.

If that is so.....we should attempt to SLOW the pellets speed down the deck DOWN. the FPM, or foot per minute travel of the product on a 20 deg inclined screen calculation by VSMA and others assumes we are travelling at plus minus 60FPM range to 75FPM range Depending on which companys formula is actually being used. some are more liberal or conservative than others.

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So how do we slow the product down??? We can install old conveyor belting curtains across the width of the TYROCK say within 3/4" of the deck surface or closer to slow the FPM down and allow the pellets the opportunity to attempt to pass the opening. Restricter DAMS can be supplied by your Rubber supplier to help slow down. You could try slowing the RPM of the screen down to see how that might work.....say reduce by 50 RPM...won't hurt anything...worth a try.

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On a new installation, you could have a lower install angle say 10 degrees vs 20 because of the rounds and accelerated FPM rates...

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A tip......to calculate actual FPM of actual product.....spray bomb say flourescent orange, yellow whatever some pellets. Toss them on the feed end of the good ole trusty TYROCK...and time with your watch...number of seconds to pass off the discharge lip. This will will a percentage of 60 seconds or one minute. Multiply to get to one minute.....and you got er.

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Ohhhhh.... also...you reverse the motor leads....to run the TYROCK uphill.....or counterflow rotation vs directional rotation..THIS WILL retain the pellets on the deck longer and increase the screening EFFICIENCY.

Wishing you an EFFICIENT result from all of this......Keep Smiling

George Baker Moderator ■