Choosing the Right Crusher
When choosing a new rock crusher, it’s important that you find the right one the first time. This not only saves you time, but it will also save you money in the long run.
According to Russ Coverdale, Applications Manager, the first thing you need to know is which machine best matches your material.
Geology is very important in this instance. You need to know what type of material you’re working with, whether it is sandstone, limestone, or granite. Since the characteristics of each stone are very different, you must determine if you need a compression style crusher or an impact style crusher.
Knowing the material you’re going to crush will help point you in the right direction of which type of crusher you’ll need. You’ll need to know how difficult it is to crush the material, as well as how abrasive it might be. Some materials contain high amounts of silica, such as sandstone for instance, which is a more abrasive material that wears your liners out quicker. Versus something that might not be very abrasive, such as a marine limestone.
Compression Crusher or Impact Crusher?
Once you understand the material you’ll be crushing, then you need to decide which type of crusher is right for you. Compression style crushers, such as a jaw crusher or a cone crusher, are typically used with more abrasive materials. Impact style crushers, such as a horizontal shaft impactor or a vertical shaft impactor, are used more for material that is less abrasive.
Some plants will use both styles of crusher. For example, the end result can also determine what type of crusher you need. If the shape of the stone is an issue, an impact crusher will give you a little better shape and give you more cubicity in the final product. Many times, customers will have existing plants that have crushers that generate significant amounts of flat and elongated pieces. They may have somewhat of an abrasive stone, but they could introduce an impact style crusher down the line to help shape the material.
Newer generation cone crushers – from the late 1980s on – made significant changes in the stroke and the throw and speed of the machines and that lends itself to a more cubical product. Cubicity can be better controlled with those types of machines, provided you don’t exceed what we call the ratio of reduction, meaning just how far we are crushing a rock in a single stage.
Dealing with Slag
Another material you might work with is slag. Slag is produced during the process of smelting or refining ore. There are different types of slag which call for different types of crushers.
With blast furnace slag, it’s not as abrasive or as hard as steel furnace slag. Blast furnace slag has just come out of a based oxygen furnace and all that’s been added to it are iron ore pellets, which helps make molten iron. The slag that comes off of that is not as hard and dense as steel slag.
Steel slag is what happens when molten iron is introduced to other elements needed for steel, such as nickel, chromium, and manganese. The steel slag is much harder, making it harder to crush because of its higher compressive strength. According to Coverdale, if you’re crushing steel slag, you want to use a compression style crusher, and when you’re crushing blast furnace slag, you can get away with impact style crushers from time to time.
In a slag plant, you’re after the metal. You want to be able to recycle it and sell it back to the mill. Many of these machines will use a tremendous number of magnets to remove the metal and separate it out so that the slag product itself can be used in the construction industry for cement, or even asphalt on roads.
Protecting your Crusher
There are many types of protection devices on these machines to help protect it from damage. For instance, a jaw crusher has a toggle plate on it, which is a safety fuse. If you were to get an uncrushable into that chamber, the toggle plate will bend or break before you do major damage to the bearings or shafts. Cone crushers are equipped with tramp relief systems on them that allow for uncrushables to pass through without damaging the machine.
The aggregate industry is a little different. Tramp metal is an issue and it’s something that could get loose in the plant. If the metal gets through, typically metal detectors and magnets can remove them, but you want to try to protect your crushers prior to that point. Unfortunately, jaw crushers get the least protection because it’s taking the raw feed coming in from the pit.
Don’t Decide Before You Know All the Facts
Sometimes people have preferences based on the type of machine they’ve always used. They may have misconceptions about the newer generation crushers, such as they might result in too many fines.
That’s something that can be fixed by adjusting the speed or the way the circuit is set up. This allows people to have the new technology and a machine that outperforms what they’re used to. Also remember that every quarry is different, so just because one company does something one way doesn’t mean you can automatically do it the same way.
Something to also consider, just because one crusher might be cheaper, doesn’t necessarily mean it’s the best one for you. For example, a customer decides he wants to get into the crushing business and sees that an impact crusher may be cheaper than a cone crusher. The customer then buys the impact crusher because it’s cheaper, but if they’re mining an abrasive stone he will end up changing the blow bar and liners much more frequently than he would in a compression style crusher. At the end of the year, he may spend the same amount of money he would have spent on the cone crusher, just in wear parts and downtime in changing those parts.
Be Completely Honest with Whatever Company You Use
The most important advice overall is, if you’re looking for a new crusher, make sure you give whomever you’re working with as much information as you can.
They’re going to want to know the distribution of the size of the material going into the crusher. The largest piece obviously dictates the feed size opening. Another important thing they’ll want to know is just what market you serve – do you produce a lot of concrete stone, which tends to be coarser aggregates, or do they produce a lot of asphalt stone, which are somewhat finer. That can be answered simply be saying if there’s an asphalt plant outside of your quarry or is there a concrete plant outside of your quarry. You’ll definitely have a target on what you want to produce, so be upfront with the person you’re working with, let them know everything so that they can better serve your needs when setting up your system.
At the Mellott Company, we’re here to help you find the right crusher. Contact us today at 800-634-5634 or email at [email protected] for more information.Back to news