Jaw crusher output capacity calculation method explanation

Jaw crusher output capacity calculation method explanation

Jaw crusher output capacity (also called throughput, unit: t/h) refers to the mass of qualified discharged material produced per hour under specified working conditions. The calculated value is a theoretical reference; actual on-site capacity is affected by rock hardness, feed size, moisture, CSS (closed side setting), feeding uniformity and liner wear.

1. Basic Empirical Formula (Most Widely Used in Mining & Aggregate Industry)

Q = K × q × b Where:

  • Q: Jaw crusher theoretical capacity, t/h
  • K: Comprehensive correction coefficient (0.24 ~ 0.5 for single toggle jaw crusher; 0.5 ~ 0.7 for double toggle jaw crusher) K considers rock compressive strength, bulk density, feed gradation, feeding continuity, jaw plate condition. Hard rock & poor feeding → smaller K; soft rock & uniform feeding → larger K.
  • q: Unit width capacity, t/(h·mm). It is the throughput per 1 mm of discharge gap, look up from manufacturer technical table.
  • b: Closed side setting (CSS), mm, the minimum gap between fixed jaw and movable jaw at discharge position.

Simplified alternative formula for quick estimation:

Q = 0.36 × L × b × ρ

  • L: length of jaw plate (cm)
  • b: CSS gap (cm)
  • ρ: bulk density of crushed material (t/m³, typical 1.3~1.6 for crushed stone)

2. Key Parameters Affecting Capacity Calculation

  1. Closed Side Setting (CSS) The most direct factor. Larger CSS → bigger discharge particle → higher throughput. Reducing CSS will significantly drop output.

Note: Do not confuse CSS with OSS (open side setting). Capacity calculation always uses CSS.

  1. Material Bulk Density & Hardness Limestone (soft-medium, bulk density ~1.4 t/m³): higher capacity. Granite / basalt / iron ore (high hardness, bulk density ~1.5~1.6 t/m³): lower capacity, bigger wear loss. Wet & sticky material: easy blocking, actual capacity may decrease by 20%~40%.
  2. Feed Size Ratio If raw feed size is close to feed opening, material bridging occurs, throughput falls. Ideal condition: feed size ≤80% of crusher feed opening.
  3. Crusher Type
  • Single toggle jaw crusher: higher stroke, larger capacity, widely used in quarry, mining, construction waste.
  • Double toggle jaw crusher: smaller stroke, lower throughput, for extra hard abrasive ore.
  1. Jaw Plate Wear Worn jaw plates change cavity profile, reduce effective crushing space, output gradually decreases.

3. Calculation Example

Model PE600×900 jaw crusher

  • Jaw plate length L=90 cm
  • CSS b=4 cm
  • Crushed granite bulk density ρ=1.5 t/m³ Q = 0.36 × 90 × 4 × 1.5 = 194.4 t/h (theoretical value) Actual on-site capacity: 160~180 t/h after applying correction coefficient, due to feeding fluctuation and rock hardness.

4. Difference Between Theoretical Capacity and Actual Capacity

Theoretical capacity: calculated under ideal continuous feeding, dry material, new jaw plates. Actual capacity = Theoretical capacity × working efficiency factor (0.7 ~ 0.95). Common reduction factors:

  • Irregular feeding, material bridging
  • Wet sticky raw material
  • Worn jaw liners
  • Intermittent loader feeding
  • Mix tramp iron or soil

5. Practical Calculation Steps for Site Engineers

  1. Confirm jaw crusher model, get jaw plate length and recommended CSS range.
  2. Test or check bulk density and compressive strength of raw rock.
  3. Select proper comprehensive correction coefficient K.
  4. Compute theoretical throughput.
  5. Multiply by site efficiency factor to get real expected output.
  6. Adjust CSS if production target does not match.

6. Important Reminders

  1. Manufacturer catalog capacity data is tested under standard conditions, only for reference.
  2. Narrow CSS improves finished aggregate fineness, but sacrifices output. Balance capacity and particle size.
  3. Overfeeding cannot increase capacity, but causes cavity block and overload.