- A tonnage figure alone does not define a crushing plant, the author says.
- Feed size, moisture and clay affect which equipment will work.
- Buyers should define the required product before comparing quotes.
- Closed circuits can overload screens and conveyors, the author says.
A REQUEST for a crushing plant often starts with one number: 100, 150 or 200 tonnes per hour. It is a useful starting point, but it does not yet tell a supplier what the plant has to do.
A quarry trying to make several saleable stone sizes and a gold-ore operation preparing material for a mill may ask for the same hourly capacity. They are not asking for the same circuit.
Before looking at crusher models, it is worth settling three questions: What exactly will enter the plant? What must come out? And what has to happen between the two? Most of the expensive misunderstandings begin when one of those answers is left open.
The feed is more than the biggest stone
The largest lump matters because it affects the feeder, crusher opening and the way material enters the chamber. But the rest of the feed matters just as much. A pile containing occasional large rocks and plenty of smaller material behaves differently from a consistently coarse, blocky feed.
A useful first description should include the material type, the largest expected piece and a representative idea of the size distribution. Photos with a scale are helpful, but where the investment justifies it, sampling and size analysis tell a more reliable story. One attractive photograph of clean rock should not be used to describe an entire deposit or borrow pit.
Moisture and clay are worth discussing early. Material that feeds and screens well when dry may become difficult to handle after rain. Fine, damp material may stick to the hopper or blind a screen.
In that situation the limiting point may be the feeder or screen rather than the crusher. Likewise, hardness, abrasiveness and unwanted metal affect machine choice, wear and maintenance. Uncertain or variable material properties may require testing before final sizing.
Start from the product, then work back
‘Crushed to 20 mm’ can sound precise, but it is not necessarily a finished-product specification. Does the buyer need one broad product, several closely graded fractions, or material of a suitable size distribution for the next grinding stage? Does the product have to meet a particular contract grading? Those are different duties.
For a quarry, a screen may be needed to separate the crushed stone into distinct products. Oversize may have to return for another pass. For an ore-processing project, the next stage may be a ball mill or another separation process, and a stable feed size distribution can matter more than making the crusher discharge as small as possible.
The discharge setting of an individual crusher does not, on its own, guarantee the final plant product.
This is where a seemingly cheap quotation can become misleading. A price for a primary crusher is not a price for an operating plant that produces the buyer’s required material. Feeders, screens, conveyors, return arrangements, chutes, controls, wear parts and installation scope all need to be understood before comparing proposals.
A plant has more than one capacity
It is also important to agree on what ‘150 tonnes per hour’ means. Is that fresh material entering the plant, material passing through one crusher, or saleable finished product leaving the screens? The numbers can be very different.
In a closed circuit, some material rejected by the screen goes back to a crusher. The screen, return conveyor and secondary crusher can therefore handle more material than the fresh-feed figure suggests.
If these components are sized only for incoming tonnes per hour, the internal circuit can become the bottleneck even when the crusher has spare capacity.
Operating hours are another missing detail. A plant required to produce a daily target in a short shift has a different duty from one running steadily over longer hours. Stops for inspection, liner changes and housekeeping also need to be considered.
A nominal machine rating should not be presented as a guaranteed production figure for every material or site.
The layout must work on the actual site
A crushing arrangement that looks tidy on a diagram still needs space for truck approach, feed stockpiles, product separation, dust control, safe access and wear-part replacement. If the working face is likely to move, the cost and frequency of relocating the plant also matter.
A mobile unit can shorten an upstream haul, but the finished material must still reach its next destination.
Power availability, foundations or ground conditions, access roads and the ability to obtain spares should be raised before equipment is ordered. These are not afterthoughts for commissioning: they can change which arrangement is practical in the first place.
What buyers should provide
At the enquiry stage, the buyer does not need every answer. A short, honest brief is enough to begin: material and source, expected maximum and typical feed sizes, moisture or clay condition, hourly and daily production targets, required products, available power, and a simple site sketch.
Mark unknown information as unknown rather than filling the gaps with guesses.
A good equipment proposal should then explain its assumptions. It should state which capacity is being quoted, what size range it expects to accept, what products the circuit is intended to deliver, what auxiliary equipment is included and which conditions still need to be confirmed.
That gives the mine or quarry operator a fair basis for comparison — and gives the supplier a better chance of proposing a plant that will actually suit the job.
