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Crushing plant capacity utilization rate explained
Why the crushing plant capacity utilization rate decides your month
The hourly rating printed on a datasheet describes what a machine can deliver with correct feed, correct material and no interruption. The tonnage that crosses the weighbridge at month end is a different number entirely. The crushing plant capacity utilization rate is the bridge between the two: it splits time into layers, assigns every lost hour to a named cause, and then verifies with scale records how much material actually passed during the hours that remained. Arguing about the rating is pointless; finding the owner of the lost hour is the substance of plant efficiency work.
Four time layers, four different questions
Most utilization arguments are really definition arguments. Fix the denominator first and keep each layer as a separate line on the shift sheet.
| Layer | What it contains | Example month (hours) |
|---|---|---|
| Calendar hours | 30 days × 24 hours, nothing deducted | 720 |
| Planned production hours | 26 working days × 2 shifts × 8 hours, planned maintenance removed | 416 |
| Running hours | Breakdowns, blockages, feed gaps and power cuts removed | 353 |
| Effective producing hours | Motor turning and the feed opening genuinely full | 318 |
Against calendar time this plant sits at 49 per cent; against planned time its availability is 84.9 per cent. Both figures are correct and they answer different questions. The first tells the owner how much of the asset is asleep, the second tells the shift supervisor how much is leaking inside the working window.
Measure the three factors separately
A single blended percentage hides the department that is actually failing. Availability, performance and quality are measured on their own and multiplied at the end.
| Factor | Formula | Worked example | Result |
|---|---|---|---|
| Availability | Running hours ÷ planned hours | 353 ÷ 416 | 84.9% |
| Performance | Actual tonnes ÷ (rated tph × running hours) | 27,400 ÷ (100 × 353) | 77.6% |
| Quality | Saleable tonnes ÷ total tonnes | 26,300 ÷ 27,400 | 96.0% |
| Overall effectiveness | Product of the three | 0.849 × 0.776 × 0.960 | 63.2% |
A weak performance factor usually points at haulage rather than at the crusher: a feeder waiting for trucks is a line whose motors turn while nothing is reduced. A weak quality factor points at screen media, at the closed side setting, or at a stockpile that drifted outside its grading envelope.
Turning a rating into a shift figure
The same effectiveness percentage means very different tonnages across machine sizes. The table below takes the lower bound of the published capacity range and applies 63 per cent effectiveness over a sixteen-hour two-shift day.
| Model | Rated capacity | Maximum feed size | 16-hour day at 63% (approx.) |
|---|---|---|---|
| General 640 | 40-70 t/h | 500 mm | 400 t |
| General 800 | 80-120 t/h | 600 mm | 810 t |
| General 950 | 120-180 t/h | 800 mm | 1,210 t |
| GNR-MC110 | 200-300 t/h | 900 mm | 2,020 t |
Sizing a plant from this column is safer than sizing it from a brochure headline, and a detailed capacity selection comparison carries the same arithmetic through the model range.
Give every lost hour a code
An uncoded stop becomes an argument at month end. Eight to ten codes are plenty; what matters is that each stop lands in exactly one of them and that its length is recorded in minutes.
| Code | Typical event | Factor it reduces |
|---|---|---|
| Mechanical failure | Belt tear, bearing replacement | Availability |
| Blockage | Bridging in the jaw, choked chute | Availability |
| Feed gap | Late trucks, blasting in the pit | Performance |
| Adjustment and sampling | Screen media change, gradation sample | Performance |
| Off-specification material | Contaminated fraction, out-of-grade pile | Quality |
No instrumentation, no calculation
Three data sources are enough: the weighbridge for tonnes, the motor hour meter for time, and the shift sheet for causes. Where no weighbridge exists, a belt scale or a disciplined truck count is a workable start, though an estimated tonnage produces an error band too wide for investment decisions. Daily entry beats a monthly reconstruction every time, because the reason for a stoppage disappears from memory within a week.
Read together, those three sources expose patterns that daily firefighting hides: stoppages cluster at the start of a shift during the cold start, and in the final hour once haulage has left the site. Across a month those minutes cost more hours than one spectacular failure, yet they never appear on a repair invoice.
Frequently asked questions
Should the rate be reported against calendar or planned hours?
Use calendar hours when the conversation is about return on the asset, planned hours when it is about shift execution. Publishing both side by side prevents the metric from being reshaped to fit the argument.
Which end of the rated range should the calculation use?
Hard, abrasive feed sits near the lower bound; soft and dry feed sits nearer the upper one. When in doubt, calculate with the lower bound: surplus tonnage causes no problem, a shortfall causes a contract dispute.
What counts as a good overall figure?
There is no universal threshold worth quoting. What matters is the trend of your own plant on comparable material over three months, and the reason behind any decline.
Cut your shift sheet down to three columns this week: minutes run, stop code, weighed tonnes. Four weeks of honest records will show which factor is holding the line back, and our team will map that record onto your specific circuit model by model.
Definitions of technical terms: Glossary
