Lesson 2/Learning Event 3
A production factor then must be applied to the 75 tph plant's jaw crusher capacity to compensate for the type
rock being crushed. This is due to the fact that tough rock require more crushing time than more friable rock.
Table 6 provides toughness factors and production factors for various types of rock. Assume the rock to be
crushed is fine grained granite. From Table 6 the production factor is 0.80. Therefore the adjusted jaw capacity
due to the toughness of the rock is:
75 tph x 0.80 = 60 tph
TABLE 6. RELATIVE TOUGHNESS OF ROCKS
Note. The includes maintenance factor.
ROLL CRUSHER PRODUCTION RATE
The roll crusher capacity depends on the size of the rolls, type of rock and the product setting. For example, you
have a roll size of 30 inches by 24 inches with a product setting of 3/4 inch. Table 7 can be used to determine the
roll capacity. From the table, 65 tons per hour is the unadjusted capacity for this example.
As in the case of the jaw crusher, a production factor must be applied to compensate for the type of rock being
processed. In this example, you are crushing fine grained granite. Referring back to Table 6, the adjusted roll
65 tph x 0.80 (from Table 6) = 52 tph.