Score Big With the Right VSI Crusher

Score Big With the Right VSI Crusher
With a VSI crusher, material is fed through the hopper to the rotor impact system that does the fracturing.

Aggregate processing is much more than just crushing aggregates and minerals. This specialized industry requires equipment that optimizes efficiency while reducing maintenance and overhead costs. A vertical shaft impact (VSI) crusher is one tool to help you meet those goals. Understanding different VSI crusher configurations will ensure you invest in one that best meets the needs of your operation. 

Break it down

VSI crushers have two main sections — the component that throws material, which can either be a closed rotor or an open shoe table, and the fracturing surface at which rocks or minerals are thrown, which is either a rock shelf or anvil ring. 

Feed material drops through the feed tube onto the impeller table or enclosed rotor, which, through centrifugal force, throws the material against stationary anvils, made up of composite metal alloys. When the rock impacts the anvils, it shatters along natural stress lines, creating a uniform, cubical product. 

Rotor: An open and closed decision

The Los Angeles abrasion test method indicates aggregate toughness and abrasion characteristics. An open shoe table works best for processing soft materials such as slate or limestone. When processing materials that are around 26 to 32 mm on the L.A. abrasion spectrum, the shoes can last 30 hours or more. This low-maintenance option minimizes costs, but run more abrasive materials through an open shoe table, and you could be replacing shoes as often as every six hours. 

For extremely abrasive materials such as gold ore or granites that register 17 mm or smaller, a closed rotor system is much more effective and requires minimal maintenance. Many units feature heavy-duty tungsten carbide pins that trap material to build up internal shoe systems. Since there are no shoes to replace, these machines don’t need as much maintenance. Some crushers also include bolt-on components that can be replaced on site to minimize downtime. 

Choosing between a closed rotor or open shoe table is a simple decision if you know what material you’re processing, but selecting the right fracturing surface involves a more economics-based approach. 

Fracturing surface: The heart of the matter

In a rock shelf system, the unit crushes rocks or minerals, which build up to form a shelf on an open ring. The biggest downfall of this design is that when material impacts the shelf it moves, shifts and absorbs energy that could otherwise be used for breaking.

The results can be gradation of only 54 percent in a single pass and the need to recirculate nearly 50 percent or more of the material. Rock shelves also run at high speeds, so adding a larger motor and more kilowatts can increase production costs by as much as $2 to $3 per ton. 

A more economical option is an anvil ring that features a series of heavy-duty, 28 percent chrome white-iron stationary anvils. Nearly all of the energy goes into fracturing or crushing the material that is propelled at the anvils, so there is very little energy absorption or material rolling.

Anvil units can reach 97 percent gradation in the first pass, and they require only 1.5 hp/ton versus 3 hp/ton on a rock shelf system. 

In addition, users can sometimes rotate and reuse the entire face of the anvil before it needs to be replaced, which significantly extends the unit’s life.

With increased productivity, efficiency and energy savings, most applications with an anvil unit will result in a 30 percent increase in profits. 

Game total

Finding the right VSI crusher configuration for your operation can increase efficiency, boost productivity and grow your bottom line. And when you have the right one, you’re sure to have a winning score. 

About the Author

Neil Hise is president of CEMCO Inc., a vertical shaft impact crushing technology and contract manufacturer headquartered in Belen, N.M. Hise has been with CEMCO since its inception in 1962 when it began as a crusher repair and service business. He became president in 1980 and is the second generation to operate the family-owned company.

He holds numerous U.S. patents on VSI-related technologies and is a member of several industry associations, including the National Stone, Sand and Gravel Association and the National Association of Manufacturers. For more information or to contact Hise, visit www.cemcoturbo.com.



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