At a glance, crushing in mining may seem simple: turn big rocks into little rocks. But in reality, it’s often one of the most demanding parts of the mineral processing flowsheet. And despite decades of advancement in equipment design and plant engineering, sites still struggle with blockages, excessive fines, runaway maintenance and mismatched machines.
Part of the problem is that we tend to think about crushing through the lens of equipment type instead of understanding the biggest driver of how a crusher actually performs: the feed itself.
During a recent episode of McLanahan’s Groundwork Podcast, Bevan McLachlan, Development Group Manager, shared another approach to crushing that starts by categorising the feed in one of three ways: the feed is the product, the feed contains the product, or the feed is in the way of the product.
This simple framework helps operators rethink what they actually need from a crushing circuit.
When the Feed Is the Product
In some operations like limestone, phosphate, potash or silica sand, the rock coming in is essentially the same rock going out. The crushing circuit’s job is primarily about size reduction and shape control.
Here, the priorities are relatively straightforward: consistent product, low fines and predictable throughput. Traditional compression crushers such as jaws and gyratories work well because the material is relatively uniform, behaves predictably and doesn’t introduce the problems that moisture, clay or contamination create. They also tend to offer reliable performance with manageable wear costs on this type of feed.
However, this scenario isn’t universal, and assuming every orebody behaves this way is one of the root causes of poor machine choice.
When the Feed Contains the Product
In most metalliferous operations, the valuable mineral is locked within the rock, and the purpose of crushing shifts from simple reduction to liberation.
This makes things more complex. Crushing too aggressively creates fines that are costly to handle and can turn saleable mineral into unrecoverable waste, but crushing too gently increases recirculating loads and reduces availability. Some deposits fracture into long, slabby pieces that create flow issues further downstream, and hardness can vary dramatically across the same pit, making the behaviour of the feed unpredictable.
Suddenly, equipment isn’t selected based on what it can do, but what it should do to strike the right balance between throughput, liberation and downstream handling.
In these operations, the right crusher isn’t necessarily the one that delivers the most force but the one that creates the right type of breakage for the orebody. That might mean using a machine with a slower, more controlled breaking action, like a sizer, which pulls material apart instead of simply compressing it. Or it may mean using a cone crusher, which deals more consistently with slabby or unevenly fractured rock.
Understanding the true behaviour of the material can improve liberation, reduce fines and produce a much more stable feed for the rest of the plant.
When the Feed Is in the Way of the Product
This is the most difficult category and the one becoming increasingly common as mines dig deeper and encounter more clay, moisture and contamination.
Sticky or wet feed can choke or slow compression machines. Operators may turn to high-pressure water to clear the chamber, only to create new issues with belts, power draw and water consumption. Oversize rocks, meanwhile, can wedge and lead to dangerous clearing practices.
In these environments, choosing the wrong crusher can be expensive, inefficient and unsafe, and is almost always a result of misreading the feed. Treating sticky, variable, moisture-rich material as if it were a clean, uniform orebody guarantees blockages, downtime and blown-out OPEX.
Recognising this feed-type early opens the door to alternatives that deal with it far more effectively. Sizers, for example, use a high?torque shear that naturally self?cleans and resists clogging – particularly if the material has been pre-conditioned through a wobbler feeder. And for some feeds, a feeder-breaker might be the better choice, combining feeding and breaking into one machine, handling big lumps with ease and reducing the overall plant height, all while minimising fines and improving maintainability.
For the right feed type, these machines deliver smoother operation, better safety and lower running costs.
Why Misreading the Feed Leads to Bad Decisions
Across all three categories, the same pattern emerges: most crushing underperformance comes from applying the wrong crushing philosophy to the wrong feed.
Many sites rely on averages instead of true distributions. Contaminants can be underestimated, hardness variations overlooked and product size requirements may be specified without realistic safety factors. And often the crusher is chosen simply out of familiarity rather than because it fits the material.
Better crushing starts with better understanding. Collecting detailed feed data makes the right equipment choice far clearer, and doing so reduces fines, improves safety, prevents blockages and keeps downstream processes running as they should.
At its core, good crushing comes from understanding the material you’re working with. When you start with the feed, selecting and running the right crusher becomes far easier and far more effective.
