Jaw and Cone Crusher Myths & Total Operating Costs

Impact Crushers Process Soft- to Medium Hard Rocks Without a Primary Crusher

A common misperception is that impact crushers struggle with hard rock and in primary crushing applications. This is far from the truth. This article clarifies what applications can be done by mobile impact crushers instead of traditional jaw and cone crusher setups.

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Abrasiveness, feed size, and material hardness are the 3 main determinants if you can use an impact crusher over a jaw and cone crusher train.

• Abrasiveness describes the property of the rock that causes wear by friction. Silica content in your rock is a driver for material abrasivness.
• Feed size describes the largest input piece dimension diameter.
• Material hardness has a significant affect on crusher performance it doesn't exclude an impact crusher from processing hard rock. The harder to rock gets the smaller the feed size needs to be to avoid damages. Besides material hardness the break resistance is also important. In other words, material can be hard but still break easily.

 

Everybody talks about wear but nobody about the reduction ratio

Inexperienced salesmen put forward impact crusher wear costs which are higher than for compression based jaw and cone crushers. The statement without context is true but omits one essential fact: an impact crusher works harder to downsize material. In other words, an impact crusher can reduce the material significantly more than a jaw and cone crusher. The ratio of input size vs the output size describes the so-called reduction ratio.

Common reduction ratios and feed size example:

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Reduction ratio example: jaw, cone, impactor   Maximum reduction ratio Feed material Output size Jaw crusher 6:1 24" 4" Impact crusher 24:1 24" 1" Cone crusher 5:1 4" 0.8"

 

10 reasons to replace your jaw and cone crusher setup with a mobile impact crusher

 

If your application permits to use an impact crusher over a jaw and cone crusher setup there are numerous reasons that support the use of an impact crusher.

1. Less fuel burn: Only one machine burns fuel. For example, if you can save 8 gal / h in fuel over 1,500 hours a year at an average fuel cost of $4.50 per gallon this equates
   a saving potential of $54,000 in fuel.
2. Less maintenance costs: Less fluids and fewer grease points, conveyor belts, and filters to maintain.
3. Faster start-up and shut-down procedure: Simple and efficient procedure. Less risk to get the start-up procedure wrong. Less downtime during a blockage. For example, if your mobile impact crusher produces 300 tons per hour and saves you 30 min every day you can produce an additional 150 tons per day. Assuming you produce 150 days a year this adds up to an additional 22,500 tons of material.
4. Lower parts inventory: Instead of stocking parts for a jaw and cone crusher you can reduce your parts inventory to what is needed to operate a single impact crusher.
5. Lower moving costs: Cutting your equipment transport costs in half improves your bottom line.
6. Easier setup: Setting up a jaw and cone crusher and an additional screening plant is time consuming and need to be tuned in before you can start crushing. Jack-knifing a screening plant for a closed-circuit operation adds an additional challenge.
7. Improved material quality: Produce quality cuboid material. More chips and fine production.
8. Increased versatility: a mobile impact crusher allows you to venture into different application such as on-site concrete recycling or producing roadbase with just a closed-circuit mobile impact crusher instead of a crusher and a separate screening plant.
9. Lower training effort: Trust your guys around the machine because they need to handle only one type of machine.
10. Lower risk for downtime: If one machine is down your entire crew is down. Using a single impact crusher reduces the number of moving parts in your processing operation that can go wrong, so that you reduce the risk for downtime and increase profits.

1. Feed Hopper: Rocks are loaded into the feed hopper, which is typically located at the top of the crusher.
2. Crushing Chamber: Inside the crusher, there's a fixed jaw and a movable jaw. The rocks are fed into the crushing chamber between these two jaws. The movable jaw moves back and forth against the fixed jaw, exerting pressure on the rocks to crush them.
3. Toggle Plate: The movement of the movable jaw is controlled by a toggle plate. This plate pivots at the bottom and connects the movable jaw to the rest of the crusher assembly. It helps to transmit the crushing force generated by the eccentric shaft to the movable jaw.
4. Eccentric Shaft: The eccentric shaft is driven by a motor, and it rotates, causing the movable jaw to move up and down. This motion creates the crushing action as the rocks are squeezed between the two jaws.
5. Discharge Outlet: Once the rocks are crushed to the desired size, they exit the crushing chamber through the discharge outlet at the bottom of the crusher.
6. Adjustment Mechanism: Many jaw crushers have an adjustment mechanism that allows the user to adjust the size of the final product by controlling the gap between the two jaws.