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Ratio-of-reduction. Precisely, this term refers to the size of the largest cube that the crusher will receive, divided the size of the largest cube that it will discharge. Actually, we are not dealing with exact cubes that it will discharge. Actually, we are not dealing with exact cubes when we crush rock or ore; therefore it is more convenient, at least when discussing crushers of the compression family, to base the ratio-of-reduction upon the dimensions of the crushing chamber.
In crushers of the jaw and gyratory types the ratio-of-reduction is taken to mean the ratio of the receiving opening (measured from the top of the stationary member) , to the discharge opening, which may be “open side” or “close side,” depending upon the type of crusher, as will be explained later.
For crushing rolls, either single or double, the ratio-of-reduction is the ratio of the greatest dimension that the machine will nip, to the dimension of the discharge setting.
The hammermill is not quite so easily gauged, because of the wide disparity in the size of product possible with any one grate-bar spacing. The only fair basic of comparison with other types, therefore, is to base the ratio upon the size of the largest cube that the mill will receive, divided by the size of the product, this product to be gauged by the same standards of screen analysis that are commonly used to judge the products of the other types. |
