Reduction Ratios in Crushing
Have you ever heard of a reduction ratio? In this article, we will look at what a reduction ratio is and how you can use it to crush more efficiently.
When it comes to crushing, it is important to know that each machine will have a limit on what it can do. These limits are based on their design specs and technology. To understand a machine’s crushing limits, we use something called a reduction ratio to help work out the size of rocks you can expect your machine to break down.
Crushers come in all shapes and sizes and each uses different methods to crush materials. Each type of crusher (e.g. impactor, jaw) will have different crushing abilities. Because of this, we need to know which equipment is best for each kind of material and — more importantly — which sizes we can feed into them. For this, we use reduction ratios. But what are they, and how do we know what reduction ratios suit our machines?
What is a reduction ratio?
A reduction ratio is the size a crusher will break down feed material into. In other words, the reduction ratio of a crusher tells you how big a piece of material you can feed into the crusher for it to break it up into the desired sizes.
The reduction ratio for crushing gives us important information about how large or coarse the feed can be for the crusher to handle and how fine or small the output or product will be.
For example, a 6:1 reduction ratio means a crusher will break a 6” piece, or input, into 1” pieces on average. These ratios can determine which crushers will work the best or most efficiently based on your needs. It also gives you a rule of thumb for the limits of each machine. For example, if your machine has a 6:1 crushing ratio you would not be able to put in a 12” piece of rock and break it into 1” pieces on the first pass. This would be a 12:1 ratio.
Why the reduction ratio for crushing is so important
These ratios help increase your crushing efficiency by understanding what your crusher can do. This can help you select the right machines to increase crushing efficiency.
They also help manufacturers explain what customers can expect from a crusher as the performance depends on using the machine correctly. If you regularly load your crusher with material that is too big or try to crush material much smaller than the machine is able to do you will risk breaking the crusher, leaving you with costly repairs and long downtimes. It is much better to work within the limits of your machine and if necessary size up and get a bigger crusher.
What is the limiting reduction ratio?
The Limiting Reduction ratio — is the maximum feed size (known as F100) that can be put to the crusher and the maximum product size (p100) the crusher can produce. This ratio is a good starting point when choosing a crusher as it will give you an idea if the crusher will be able to handle the size of rocks you want to work with.
Below is a table summarising the reduction ratios for common crushers. These can be used as a rule of thumb guide. Each machine will have its own limits depending on the size of the crusher.
How can crushing reduction ratios increase crushing efficiency?
These crushing reduction ratios allow us to better understand the size of the feed materials allowed versus the output size we can expect after crushing. Understanding these ratios can give you major advantages for improving efficiency:
- Save Time — By purchasing a large enough crusher to avoid breakdowns or damage caused by feeding material that is too large for the crusher to handle and by speeding up the crushing process.
- Save Money — By not overspending on a crusher that is too large for your needs or by choosing two or more smaller, cheaper crushers in place of a larger one.
- Improve productivity — By using the right crusher to produce the product size you need without having to pass material through it multiple times.
Reduction ratios in crushing help with choosing the right equipment for the job and how many machines you’ll need based on feed and expected product sizes. This can really improve site efficiency and help avoid problems caused by rough or heavy use.
Crusher types and their ratios
Jaw Crushers
Reduction ratio — 6:1
Jaw Crushers use pressure to break up very hard, flaky, and slabby rocks by passing them between a moving surface and a stationary one. They are generally used for primary crushing but also provide great results with secondary crushing. Jaw crushers are excellent for breaking up concrete, rock and asphalt.
Impact Crushers
Reduction ratio — 10:1
Impact Crushers can be used for either primary or secondary crushing and work by creating a sudden impact force that shatters the material into smaller pieces. They often come as primary crushers (with an 8:1 crushing reduction ratio) or secondary crushers (10:1 reduction ratios) and are perfect for crushing medium-hard materials like concrete and limestone.
Cone Crushers
Reduction ratio — 5:1
Cone Crushers use compression to reduce material sizes by squeezing the feed material between a rotating cone and a crushing wall. They are used mostly for secondary crushing and are reliable tools for efficient crushing.
Conclusion
Crushing reduction ratios are really important when deciding which crushers to buy. They will help you choose the feed sizes to prevent breakdowns while producing the product shape and size that you want.
Reduction ratios help us decide which equipment to choose to make sure it works as designed without damaging or overworking these tools.
Choosing the best crusher can be a difficult process — our Machinery Partner experts are on hand to answer any questions you have. They can also talk you through the best machine for your business by chatting about the materials you work with and what you need your crusher to do.
To find out more — get in touch with Machinery Partner today or check out the full range of equipment from crushers, excavators, screeners and more — all available online at www.machinerypartner.com