dear nitesh,

the capacity of screen mainly depends upon the followings

1. width of the area where the material is being fed.

2. mesh size/size of particles

3. vibrating resolutions of the screen.

4. feed rate.outlet size,inlet size.inclination of screen.

all the above parameters are connected with each other

anil seth ■

please advise:

width and length of present screener

speed of screen box, slope or angle of screener, stroke size

Generally: wider equals more TPH

longer equals more clean or efficient screening

Mfr of screener

Is it inclined screener with circle throw stroke?

Is it flat or horizontal screener with linear stroke?

Jumping from 15 to 21 tons is not a problem as long as the screen IS NOT OVERLOADED at present setup..

Best Regards, George Baker Moderator ■

Nitesh

You can increase the screen capacity by increasing the stroke or frequency or angle of inclination. If you play with the stroke or frequency you are increasing the stress on the components - usually screens are calculated for 5g acceleration - the best solution would be to contact joest and ask them the question what the limits are. If you try to increase frequency you have to be carefull not to hit one of the natural frequency - impact test would be recommended before any changes.

regards

Ziggy ■

Nitesh,

The Joest desigantion SUE means that it is a single deck linear motion screen (excited by twin unbalanced motors) ■

Dear Sir,

The Capacity of any vibrating screen depend on the percentage open area of the screen deck.

your screen has a open aera of X sq.M after deducting the clamping and other dead areas from the geometric size of the screen.

Now when you fit a screen deck say a woven wire mesh deck, the manufacturer give you an value of percentage open area for the deck.

if you use thin wire deck the percentage open aera goes up and so more material can be screened out [Passed through].and vice versa. but thinner wires also mean low life of deck and more frequent replacement.

but if you have more of over size in the feed to pass over the deck you are left with no other choice but to change the screen--- Why because in a screen we want to keep the bed depth of the material over the screen very low otherwise if there is a very high build up of material the fines will not stratify [ come to the bottom] of the screen to get screened out

Hope my post cleared some doubts

Luck ■

You can increase the capacity (up to the point) by running the screen faster or with higher amplitude but you trade off the efficiency - the particles will have less contact with the deck and therefore the probability they will go through is smaller

Ziggy ■

Dear Sir,(Ziggy)

I have read your post regarding raising the amplitude and and increasing the speed and I would like to submit the following with the hope it would be of clarity:

i) Raising the amplitude increases the stratfication of the material and I would do that if I find the cut point and the top size are too close and misplacement of particles is high. secondly I do not want raise the amplitude very high wrt the spring constant and size of screen.

ii) secondly I will submit; amplitude and speed are not raised all at once. This is always inversely propotional Bigger Screens run at lower RPM and higher amplitude, and vice versa.

Screen running at say 800 RPM can have a amplitude of upto 18 mm top limit. I would never let it vibrate beyond 14 mm normally

1000 RPM screen Amplitude 8 to 10 mm

1500 RPM screen Amplitude within 4 mm

One more thing material on screens is always in flight and only momentarily touch the deck. The particles move in a sequence of "Micro Jumps" (Micro Throw Principle)

This is all the more the reason to limit the increase in amplitude as the deck opening has to match the length of throw too!!

Trust I have cleared some avenues of thot

Thanks ■

Dear Mr. Nitesh Seth,

In general, screen capacity can be increased by more screening area, by more amplitude of vibration and more frequency. The combination of all these parameters, is a very specialised subject and can be decided by the screen designers concerned with the profession.

There are also other important issues as below :

- If screen size is to be increased, then see whether the existing house has space for that.

- Implication on layout of the discharge chute.

- If you are increasing amplitude of frequency, its implication on the safety of the structures and foundation.

- Similarly, if you are increasing the size of the screen, its implication on the safety of the structures and foundations.

Therefore, modification in existing screen or the installation of new screen involves checking of the adequacy of the existing structures and foundation. This is important because it is concerned with the safety of the plant and the people.

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 Nitesh: Sorry, I just got back into town from CONN-AGG show in Las Vegas - all about vibrating screens, crushing, etc.

I would recommend this to all forum participants. All the experts are their expressing their view points.

Check it out at www.connagg.com

................................................................

You must identify the aperture or opening in the wirecloth to then go and use the VSMA (Vibrating screen manufacturers associaton) charts. Very good data actually works excellent as a superb calculation guideline for SPEED/STROKE/SLOPE

..........................

I will insert a chart here for CIRCLE THROW INCLINED type screening.........and on the next post........a chart for horizontal screening.

Excellent informative participation by all...........very nice to see the inter-actions take place on this forum.....love it.

Mr Vibration........keep smiling........George Baker, Moderator

Attachments

speed stroke slope pg3 incline screen chart (ZIP)

■

NITESH: here is the second chart.........if using a flat screen

Attachments

speed stroke slope pg4 horizontal charts (ZIP)

■

Dear Mr.Dirk Swartz

Could Kindly out a sketch of the second methord you have suggested.

The first idea is brilliant too. ■

Hello again: Interesting imput from all our friends......excellent.

A 40% increase is kinda large......some more questions arise:

- width and length of your Joest?

- actual wirecloth opening and wire diameter and hole shape?

- is your present unit doing a good, fair, or lousy job?



TO increase the TPH.......we must know if it is doing the job now.

From this point we can make some decisions from actual experience and then increase width of machine to increase TPH if necessary after reviewing present operating conditions.

TKS..........GEORGE

review the VSMA SIZING CALCULATION and this will show you ALL variables that go into forumula to determine if your screening machine is the CORRECT WIDTH AND LENGTH for the material, material characteristics, split desired to make your product and TPH you wish to achieve. ■