Compare Square Openings Vs. Round on a Crusher Screen

Although the long established practice of designating crusher products by "ring-size" is not compatible with present-day screening practice, there are occasions when it is desirable to convert our calculations from one shape of opening to the other. So far as the curves themselves are concerned, once we have established the shape of screen opening-round or square-we can use them for either so long as we stick to one shape throughout the process of taking off percentages-passing. If, as occasionally happens, we have to deal with both shapes of screen opening in the same set of calculations, one or the other of them must be converted to equivalent sizes of the opposing shape.

For example, if most of the screen openings are to be square, but one or two of them must be round, the round-hole sizes should be expressed in terms of equivalent square openings.

Inasmuch as the table of crusher settings versus equivalent product percentages is based on square openings, it is necessary to convert to equivalent round openings before this table can be used for such openings.

Table II contains the information we need to make conversions from round to square holes, or vice versa.

The two columns at the left showing equivalent sizes for flat testing screens, are the columns to use in connection with crusher product calculations.

Admittedly, listings of equivalent round and square boles, such as we show in this table, can be only approximately correct for the many different materials with which we must deal in crushing and screening computations. The infinite variety of shapes encountered renders absolute accuracy an impossible attainment.

Practical experience, however, indicates that the comparisons shown in our table are in most cases close enough for all practical purposes.