Lesson 2/Learning Event 2
The maximum feed size to the roll crusher determined by adding the product setting of the rolls to the stage of
reduction capability for that particular set of rolls. Every different size of rolls and combination of roll shell
surfaces is capable of a different stage of reduction. Table 3 gives the stage of reduction capability for various
sizes of rolls and roll shell combinations.
TABLE 3. STAGE OF REDUCTION DUAL ROLL
As in the above example, the product setting is 3/4 inch. For example, you know that the roll dimensions are 30 x
24 inches and that you have a fine corrugated and smooth roll shell combination. The stage of reduction
capability for this particular set of rolls is 1-3/4 inches (Table 3). Therefore, the maximum feed size to the rolls is
derived as follows:
Product Setting
3/4 inch
Stage of Reduction Capability
1-3/4 inches
2-1/2 inches
This means that the product created by the jaw crusher should not be larger than 2-1/2 inches.
The jaw crusher is always set on the closed stroke. Therefore, allowance must be made for increased particle
sizes when the jaw crusher is on the open stroke. Table 4 is used to determine the jaw setting required to produce
a certain size aggregate. In the above example, the maximum size product created by the jaw crusher can be no
larger than 2-1/2 inches. Therefore, from Table 4, you find the correct jaw setting will be 2-1/4 inches.
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