Lesson 2/Learning Event 2
aggregate is because somewhat oversize particles can pass a given screen opening size when oriented diagonally.
By calibrating the plant to produce a top size of 3/4-inch aggregate, a safety margin of 10 percent is provided in
the event the product stockpile may contain aggregates over 3/4 inch but less than 1 inch. The same reasoning
holds true on the minimum product size. Calibrate the plant to produce 3/8-inch aggregate as the minimum size,
thereby creating in this case, a 15 percent leeway for particles in the stockpile being less than 3/8 inch. Therefore,
you should choose the next smaller se screen than the given maximum specification size for the upper size
calibration. Similarly, you should choose the next larger size screen than the given minimum specification size
for the lower size calibration.
However, it is necessary to select screens with openings slightly larger than the size products desired, due to
screen inefficiency caused by the angle of inclination, throw, and angular particle shapes. Table 2 is used for the
selection of screens. This table shows the relationship between product size and screen size.
TABLE 2. VIBRATING SCREEN SELECTION CHART
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