The capacity of a jaw crusher is determined by the size of the feed opening (gape), the closed-side setting (CSS), the speed of the jaw, and the stroke (throw). The theoretical capacity can be estimated using empirical formulas. Here are some commonly used formulas for calculating jaw crusher capacity:
1. Hersam’s Formula (Empirical Approach)
\[
Q = \frac{60 \times N \times S \times L \times W}{1000}
\]
Where:
– \( Q \) = Capacity (metric tons per hour, tph)
– \( N \) = Speed of the jaw (rpm)
– \( S \) = Stroke at the discharge end (mm)
– \( L \) = Length of the crushing chamber (mm)
– \( W \) = Width of the discharge opening (closed-side setting, mm)
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2. Taggart’s Formula
\[
Q = 0.93 \times W \times S \times N \times d_{avg}
\]
Where:
– \( Q \) = Capacity (tph)
– \( W \) = Width of crusher feed opening (m)
– \( S \) = Open-side setting (m)
– \( N \) = Jaw speed (rpm)
– \( d_{avg} \) = Average density of material (t/m³)
3. Simplified Capacity Formula
\[
Q = 1.25 \times L \times CSS \times s \times n
\]
Where:
– \( Q \) = Capacity (tph)
– \( L \) = Length of feed opening (m)
– CSS = Closed-side setting (m)
– \( s \) = Stroke at discharge end (m)
– \( n \) = Jaw speed (rpm)
Key Factors Affecting Jaw Crusher Capacity:
1. Feed Size & Hardness – Larger or harder materials reduce capacity.
2. Closed-Side Setting (CSS) – Smaller CSS increases fine output but reduces throughput.
3. Jaw Speed & Stroke – Higher speeds increase capacity but may cause excessive wear.
4. Material Density – Heavier materials reduce volumetric capacity.
5. Crusher Design – Different jaw profiles and motion affect efficiency.
Practical Considerations:
– Actual capacity may be lower due to feed gradation, moisture, and operational conditions.
– Manufacturers often provide performance charts based on empirical data.
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