SANDEEP: How are you doing today?

First of all, VSMA is a general ASSUMPTIVE guideline of historical operating data made up of actual manufacturing companies that have vast experience in vibrating screen applications. The manufacturing industry is about 100 years old or so.

Depending on which specific company you pick for a vibrating screen manufacturing supplier - the specific formulas are going to be more CONSERVATIVE or more LIBERAL. Most tend to be more conservative on in other words (wrong on the safe side) ......so to speak. If the sizing is going to be incorrect the machine will be bigger vs smaller in most instances...(to make sure we have enough machine to do the job).

Some companies will bid jobs on the LIBERAL side or cheaper capital cost side to ensure winning the contract and the machines may in fact be MARGINAL to do the job. They win the contract but, could have problems after startup.

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Another very critical important point to clearly understand.

VSMA is not the be all and end all. It is truly just a mathematical calculation inserting known variables to support known datas. Even if we come to the end of the calculation and it says for example (120 square feet of screening area is needed). THIS DOES NOT MEAN......a 6x20 screen is the pick.

The formula math says IT IS THE PICK, right? Wrong.

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To this we must apply the ART or screening application technology. This is the knowledge of an experienced field person or manufacturing person that knows we must increase the size of the machine. They know from past in field experience that the material has strange characteristics such as non free flowing, blinding, sticking or anything else that may require a large screen area or special ball tray deck to clear or special urethane panels or wirecloth slotted openings. Yes, these variables are all in the formula........but, to that we add ACTUAL field personnel knowledge to assess the proper size needed.

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And lastly, and mostly missed by people when sizing screening machines. BED DEPTH MUST BE CALCULATED always before finalizing the screener width and length. This is clearly described in VSMA. General rule of thumb.....THE BED DEPTH of the material being screened - must not be more than 3 times the opening size in the wirecloth. For example: say wirecloth opening is 1/2" clear .......VSMA says we do not want more than 1 1/2" bed depth of material at the DISCHARGE end of the screen, so we can maintain EFFICIENT screening as per the VSMA formula.

Another words, if I am say........4" deep by say surge loading or overloading the screener......I will have CARRYOVER of fines that should theorectically and in practice pass the OPENING.

They in fact will NOT PASS, because the BED DEPTH is too deep, The fines can not get down to the opening to pass because the MAT of material is too heavy or deep to allow them to pass.

Lastly, manufacturer's who do a lot of coal desliming and coal applications have specific knowledge, pertaining to specific applications. ONCE again VSMA is just an assumptive guide but, completely useable.

ALLIS CHALMERS sizing guidelines would be a very good pick on coal desliming due to long history. Changed to SVEDALA and I think now owned by METSO. Fun eh?

The speed stroke slope charts in fact due generally apply here.

Hoping this helps..............George ■

Should be able to get this data from METSO Minerals for sizing data. Can find on web, and if not......they could probably direct you to the source.

Inclined will do the job for cheaper capital cost but, actually I think you will find the flat or horizontal is the generally preferred device on this type of application.

Keep Smiling.... ■