Calculation Screen Efficiency Factor Formula

It should be noted that formula (1) is applicable only for 100 percent screen efficiency, something that is rarely, if ever, achieved in practice. So, to put the formula in more usable form, we must insert another factor to compensate for screen efficiencies below 100 percent. To illustrate why this is necessary, assume a screen efficiency of 90 percent for the problem just discussed. Then, on the first pass, the screen would reject, as oversize, 30/.9=331f.¡ tons; and this same differential would apply to each succeeding pass. The revised formula takes the following form:

(2)  T = 100 / (1 - R/E )

where E = screen efficiency, expressed as a decimal.
Our problem now lows appears as follows:

T = 100 / ( 1 - .7/.9 ) = 150.3 tons

 which indicates a circulating load of 50.3 percent.

To present in convenient form values derived from formula (2) we have prepared Table 1, herewith, showing theoretical circulating loads, expressed in percentages of the original feed. The table covers a wide range of oversize percentages in the crusher product, and several screen efficiencies. It is broad enough to cover almost any combination of conditions that might be encountered in actual practice.