The output of an aggregate crushing plant is determined by several interrelated factors, including the type of equipment used, the feed material properties, operational settings, and plant configuration. Accurate calculation of output is essential for planning production capacity, optimizing efficiency, and meeting project specifications.
The primary method for calculating output begins with understanding the capacity ratings of individual crushing stages—primary, secondary, and tertiary crushing—typically provided by equipment manufacturers under standardized conditions. For example, jaw crushers used in primary crushing are often rated based on feed size, closed-side setting (CSS), and material hardness. According to Metso (now Outotec) and other major equipment suppliers, a typical jaw crusher such as the Nordberg® C110™ can process between 200 and 400 metric tons per hour (tph), depending on feed gradation and moisture content (Outotec, 2021).
After primary crushing, material is conveyed to secondary or tertiary crushers—commonly cone or impact crushers—each with its own capacity curve. A standard cone crusher like the HP3™ can handle approximately 150–350 tph, influenced by CSS and feed size (Sandvik Mining, 2020). The overall plant throughput is not simply the sum of individual crusher capacities but is constrained by the bottleneck stage—the slowest component in the process chain.
To calculate actual plant output, the following formula is commonly applied:
Plant Output (tph) = (Mass of Aggregate Produced) / (Production Time in Hours)
However, for predictive calculations before operation, engineers use:.jpg)
Estimated Output (tph) = (Feed Rate × Plant Availability × Efficiency Factor)
Where:
- Feed rate refers to the volume of material introduced into the primary crusher (tph),
- Plant availability accounts for downtime due to maintenance or blockages (typically 85–95%),
- Efficiency factor includes material segregation, moisture, and crusher settings (usually 0.8–0.95).
Additionally, gradation of the final product must meet specification requirements. Screening units downstream of crushers determine how much material meets size criteria. The efficiency of a vibrating screen can be calculated using:.jpg)
Screen Efficiency (%) = (Undersize in Product / Total Undersize in Feed) × 100
This influences effective output, as material failing to pass the screen may be recirculated, reducing net throughput.
Empirical data from operating plants indicates that a well-designed aggregate crushing plant processing limestone with a feed rate of 500 tph can achieve a final salable output of approximately 420–460 tph, accounting for 10–15% loss due to fines, moisture, and rejects (Kumar et al., 2018, Journal of Materials in Civil Engineering, ASCE).
In conclusion, calculating the output of an aggregate crushing plant requires consideration of equipment specifications, operational parameters, and material characteristics. Real-world performance data and manufacturer guidelines provide reliable benchmarks, ensuring accurate output estimation for planning and optimization.