Whether designer or user, in order to properly design and use of jaw crusher and to ensure the reliability and economy of operation, must understand and master the main parameters of jaw crusher. Because the theoretical calculation error of some parameters is large and not practical, only the more practical empirical calculation formula is introduced here.
1. Dimensions of the feed port and the width of the discharge port The size of the feed port is a very important parameter when selecting the size of the jaw crusher, and it is also the data that the operator should know. At present, in China, the length L of the feed port is 1.25-1.6 times the width B, that is, L=(1.25-1.6)B. For large jaw crushers, L = (1.25 - 1.5) B; for small jaw crushers, L = (1.5 - 1.6) B. Feed port width B determines the maximum feed size Dmax of the crusher. Generally, D max = (0.75 - 0.85) B is taken. In China, the simple pendulum type usually takes D max =0.75B; the complex pendulum type usually takes D max =0.85B.
The width e of the discharge opening depends on the maximum discharge size d max and the swinging stroke S of the moving jaw. It can also be determined by referring to the feed port width B. Usually, the simple pendulum type takes e=d max -S=(1/5-1/7)B; the complex pendulum type takes e=d max -S=(1/7-1/10)B.
2. The angle of the jaw crusher is the angle between the moving jaw and the fixed jaw. During the crushing process, sufficient friction is required between the ore and the moving face to prevent the ore from sliding upward or jumping out of the feed port. The jaw angle of the jaw crusher is generally selected between 17 ° and 24 °. Correct selection of the angle of the joint has great significance for improving the productivity and crushing efficiency of the crusher. Increasing the angle of the teeth increases the breaking ratio, but at the same time the productivity will decrease. Reducing the angle of the jaws increases the productivity of the crusher, but the crushing ratio will decrease, so the designer should consider the overall consideration when selecting the angle. In foreign countries, a curve-shaped crushing cavity with a deep and small angle is generally adopted, in order to obtain higher productivity, and also ensure that the crushing ratio is not reduced. At present, China is working hard in this direction.
3. Rotating speed of eccentric shaft At present, in actual production, the following empirical formula is commonly used to determine the rotational speed n of the eccentric shaft, and the calculation result is close to the actual rotational speed. When the feed port width B < 1200 mm, n = 310 - 145 B (r / min); when the feed port width B ≤ 1200 mm, n = 160 - 42 B (r / min).
4. Productivity The productivity of a jaw crusher refers to the amount of ore processed in a unit of time. It is a quantitative indicator of the crusher's processing capacity. In the design, the following empirical formula is usually used to calculate its productivity Q:
Q=K 1 K 2 q 0 eδ/1.6(t/h)
Where K 1 - ore severability coefficient (Table 1); K 2 - particle size correction factor (Table 2); q 0 - productivity per unit discharge opening width (t/mm·h) (Table 3) .
Table 1 Ore Fragility Coefficient K 1
Ore hardness
Compressive strength / Pa
Platt hardness coefficient
K 1
hard
Medium hard
soft
1.6~2
0.8~1.6
<0.8
16~20
8~16
<8
0.9~0.95
1.0
1.1~1.2

Table 2 Particle size correction factor K 2 of coarse crushing equipment
Feed particle size D max / feed port width B
0.85
0.6
0.4
K 2
1.0
1.1
1.2

Table 3 Productivity of the unit discharge opening width of the jaw crusher q 0
Crusher specifications / mm × mm
250×400
400×600
600×900
900×1200
1200×1500
1500×2100
q 0
0.4
0.65
0.95~1.00
1.25~1.30
1.9
2.7
5. Power of the motor During the operation of the crusher, the power consumption of the crusher is related to its rotational speed, size, discharge width, angle of the teeth, particle size of the ore and its physical and mechanical properties. Since the factors affecting power consumption are many and complex, some current theoretical calculation formulas can only be used for reference when the designer first selects the crusher power. In practice, the following empirical formula is usually used to calculate.
Simple pendulum type: P≈10LHsn (kW)
Compound pendulum type: P≈18LHrn(kW)
Where L is the width of the feed opening (m); H is the calculated height of the fixed jaw (m); r - the eccentricity of the spindle (m); s - the swinging stroke of the moving jaw (m) ;n——the rotational speed of the eccentric shaft (r/min).
The above formula is summarized on the basis of the experiment, and the calculation result is close to the actual data.

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November 08, 2021