Screen Efficiency and Capacity

The performance of screens is assessed on the basis of two criteria efficiency, and capacity. 

The screen efficiency of a screen (known also as effectiveness of a screen) is a measure of the success of a screen in closely separating materials A and B. Provided the screen works perfectly, all of material A would be in the overflow, and all of material B would be in the underflow. An usual measure of screen effectiveness is the ratio of oversize material A that is actually in the overflow to the amount of A entering with the feed. These amounts are D mD and F mF, respectively. Thus 

Defining the product of the two individual ratios as the combined overall effectiveness and denoting it by E, one has the following relationship  

Substituting D/F and BjF from the earlier equations into the above equation, the final relationship is obtained as  

In industrial screening, capacity is important in addition to efficiency. The capacity of a screen is measured by the mass of the material fed per unit time to unit area of the screen. 

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