in VSMA:

circle throw screeners at 20 deg decline = 1 factor or normal

horizontal screeners at ZERO deg or flat = 1 factor or normal

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circle throw can be installed from 10 deg to 45 deg depending on the application

Horizontal linear stroke machines can be installed from 0 degrees up to 10 degrees by the rules of VSMA.....

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ONE of the reasons the linear machines in C-R is 1.2 is basically with horizontals we do not have the help of mother nature or gravity (ie 20 deg) so the 1.2 allows for the machines to be sized a little larger.....to compensate for all the action being MECHANICALLY DRIVEN by bigger motors at zero degrees.

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VSMA of course is a conglomeration of 7 VIBRATING SCREEN MANUFACTURERS ASSOCIATION (VSMA) member companies. So each company's sizing formula individually is a little more conservative or a little less conservative than each other's and the VSMA charts are a general assumptive rule of thumb...or average of all 7 to come with a BASIC SIZING FORMULA for all to utilize...........

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One is not right and the other wrong........one is just a titch more conservative than the other.....is I am making screens and my formula is a tad liberal......my screen sizes out to a smaller unit and I theoretically could sell a new machines at a MUCH CHEAPER PRICE......vs someone using a more conservative thought pattern to size.

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Lastly, assuming a 12 deg inclined unit had the same 3/8" stroke at say 850rpm range for doing say.....7/8" clear opg for sake of discussion, the formula would actually call up a WIDER screen at 12 degrees than 20 degrees TO adjust for BED DEPTH increases at 12 degrees. But, if the 12 deg unit had a much bigger stroke for sake of discussion.....and some other PLUS factors like say ball trays or special feeders to the unit or heaters or many other helpers.......than the screen with a bigger stroke etc could do the job and stay the same width (which equals more or less TPH).

Hope this did not confuse more than help. ■

Diego: sizing formula for VSMA or any vib scrn mfr are not absolutes EVER....ALL companies have slightly different factors they use for their own purposes. VSMA is in fact a compiled average of 7 companies field results and testing data.

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the VSMA formula states the following, and I quote:

"To select the size of screen, first determine, from the bed depth calculations, the width that will maintain the proper bed depth for efficient screening and choose the length that, together with the width, provides a miumum total screening area equilvalent to that arrived at in the screen area calculations."

Proper bed depth for 20 deg inclines should not exceed four times the size of the screencloth opening when separating material weighing 100lbs per cu ft. or three times for material weighing 50 lbs per cu ft.

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BED DEPTH FORMULA equation: by VSMA

BDB = O X C divided by 5 x T X W

BDB = DISCHARGE END BED DEPTH whereby:

O = OVERSIZE IN STPH

C = Cubic feet per ton of material

5 = Constant

T = Rate of Travel (Nominal 75 fpm for inclined screen at slope of 18-20 degrees with flow rotation and nominal 45 fpm for horizontal screen. (Plug in FPM rates for both types)

W = Width of Screening Area in Feet

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note the foot travel rates in the standard VSMA capacity formula above. My experience for FPM travel rates has always been 75 FPM for 20 deg incline and 45 FPM for zero degree horizontal.

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Take a stone paint it white or orange or something...throw it on your screener at feed end and time it til it discharges off the end and you will get your actual FPM or FOOT PER MINUTE TRAVEL.

IE: if you time 15 seconds, multiply that by 4 = 60 FPM.

The debate is a long one in the industry, on which outproduces which INCLINED or HORIZONTAL. Ask 10 people and you will 5 of each liking one or the other and they all are right...Their perception is their reality.

In my opinion, a 20 deg INCLINED screen will outproduce a flat screen in TONS PER HOUR all day, now a flat screen will produce more efficient CUT due to lower FPM of 45 but, the material will see the full opening better on a flat or linear or horizontal screener because it sees the WHOLE OPENING whereas the inclined material feed sees a FORESHORTENED opening....at 20 degrees. At 75 FPM it moves more TONS across the 20 degree sloped deck than a horizontal at 45 FPM.

Most companies do not have a adjustment factor for their TableII incline factor S. I would say it reflects either a differential deck design or a flat screen with the box installed with some incline on it. ■

Diego.......thankyou for the challenging question. Please continue to participate ...we do very much appreciate it.

Best Regards, ■