Why McLanahan Impact Crushers
McLanahan Corporation offers a wide selection of Impact Crushers. Whether processing soft materials like coal or hard and abrasive materials like dolomite or sandstone, McLanahan has the experience necessary to get the job done. Not only do we understand the process, but we are keenly aware of the issues that affect your bottom line. When considering an Impact Crusher, you can rely on McLanahan to analyze your application and recommend the most appropriate crusher.
McLanahan maintains the widest selection of Impactors of any manufacturer in the country. We know impact crushing can be the most efficient means to get the reduction you need. Taking into account reduction ratios, energy cost, quality of the product and maintenance cost, Impact Crushers are often more cost-effective than compressive crushers; efficiency is what we all strive for in the end.
McLanahan engineers also focus on durability. Working with foundries both domestic and foreign, we continue to support Impactors that have been in operation more than 50 years. McLanahan has earned a fine reputation in the mining and aggregates industries, and offers an extensive selection of Impact Crushers.
How Impact Crushers Work
Impact Crushers create material reduction by providing a sudden impact force that causes the material to shatter along all the weakest fissures in the stone. Controlling the flow of the material through the Impact Crusher requires features that vary from one style of impactor to another, and this is what separates McLanahan from the other manufacturers. Essentially, the material enters the crushing chamber along a controlled feed angle. A spinning rotor assembly strikes the stone with a predetermined force sufficient to cause fragmentation. The trajectory of the material is then controlled to divert the flow back into the rotor circle, where the hammers (blowbars) continue to impact the material. Adjustable curtains or similar means are used to adjust the retention of the material flow for optimum output material characteristics. The impacted material flow then exits the crusher through the base frame.
Models of Primary Impact Crushers
One of the first Andreas Impact Crushers manufactured in the USA, the McLanahan line was originally designed by Universal Engineering Corp and were introduced as primary impactors to provide easier maintenance. Andreas Impact Crushers are capable of withstanding the rigors of accepting boulder-sized feed material.
A heavy-duty rotor generates a high-intertia impact forces capable of a 12:1 average reduction ratio and provides recesses between the extra-thick rotor discs for tramp iron production. C-shaped hammers provide a more consistent gradation throughout the life of the hammer and can be vertically lifted from the rotor for reversing or replacement, resulting in more product with less downtime. Reinforced steel curtains provide the controlled material flow through the crusher and allow for quick, simple adjustments to maintain product quality.
However, these low profile impactors, while easier to make portable, do not have the expansion chamber above the rotor. Boulders enter the chamber, and the rotor is forced to shear at the bottom of the boulder until it’s small enough to shatter. Most manufacturers recommend a top size feed to their Andreas-style impactors.
The New Holland-style crushers are also known as Primary Impact Breakers. These crushers are known to take huge feed sizes and generate cubical products at better than 20:1 reduction. Its free-flow design combines a large expansion crushing chamber; a large, solid, fabricated rotor; upper deflector screen gate with vertical opening; and lower adjustable screen gate for precise product control with maximum output.
In many cases, the primary breaker is able to produce 75% minus 1-1/2”. This means 75% of the feed is already product for most base plants, leaving only 25% for further reduction at the secondary crushing stage.
As with all primary impactors, a heavy chain and rubber curtain in the feed chute reduces material from rebounding out of the crushing chamber, while also keeping dust to a minimum. McLanahan incorporates another common feature of drilled and tapped wear liners for the interior to the crusher wherever possible. This secures the liner while providing maximum utilization of the wear metal.
The MaxCap Primary Impact Crusher was introduced as a hybrid impactor combining the large expansion chamber of the New Holland with the ease of maintenance common to the Andreas Impactors. Maximum capacity of a high-quality, cubical product at a lower cost per ton can be achieved with the MaxCap.
The MaxCap Impactor accepts boulders larger than any comparable Andreas-style crusher. The feed chute in the MaxCap provides optimum feed angle and hydraulically adjusts under load to ensure continuous flow into the rotor assembly. The manganese hammers work-harden and feature a protruding leading edge to provide for optimum impact force throughout the life of the hammers. The breaker plate is hydraulically adjusted for product control, and may be used under full load, providing adjust-on-the-fly capability.
The MaxCap Impactor is available in model sizes that range from 600 tph to 1800 tph. At these tonnage rates, the MaxCap is excellent for stationary installations. The smaller models may be pit-portable, but they require more preparation for the highway.
The VersaCap P-Series and R-Series Primary Impactors are low-profile and very well adapted to portable plants. These primary impactors feature interchangeable components that can be fit to each customer's specific application. Standard two-curtain designs can be field modified to a three-curtain design, and rotor assemblies are available in three- or four-bar designs. Each VersaCap housing and rotor assembly has a heavy-duty construction and provides unmatched durability while minimizing downtime and increasing profitability.
VersaCap Impactors are engineered wih a simple hydraulic-assisted shim adjustment to minimize downtime while keeping the crusher operating at optimum performance. They are also designed with more curtain retraction than competitive designs, allowing additional tramp iron protection. In addition to the shim adjustment for the curtains, an optional semi-automatic adjust system provides adjust-on-the-fly capability with fingertip control under load. If you prefer a programmable logic controller with touchscreen, our full automation package also includes hands-free calibration.
The VersaCap R-Series Impactor is designed for highly friable material like concrete rubble, and performs well in a single-crusher closed circuit. The material passing through the VersaCap Impactor is conveyed to a screen, where the oversized material is then directed back to the VersaCap. The R-Series VersaCap may also be used in aggregate and mineral operations as a secondary crusher. The optional third curtain may also be field installed when desired.
Popular Applications for Impact Crushers
McLanahan Impact Crushers are found in a wide variety of applications. The most common is processing limestone, but any sedimentary stone and some metamorphic stone are suited for impact crushing. Impactors also operate in manmade materials with similar characteristics as sedimentary stone. Even in some rather abrasive materials, like steel slag and demolition concrete rubble, Impactors are the favored means to attain a repurposed and value-added product. In quarry operations, the use of impactors also provides a means to remove deleterious minerals. If the feed material includes soft stone, the impact force will reduce the soft stone finer than the harder rock. A screening process will then allow the soft deleterious material to pass through and out of the flow to the rest of the plant.
Benefits of McLanahan Impact Crushers
- McLanahan Impactors are designed making best use of natural forces by allowing an area for impacted materials to naturally expand along the weakest fissures, and the use of gravitational force to hold gap settings in low profile impactors
- Material control through McLanahan Impactors begins with the angle of entry into the rotor, optimum penetration into the hammer path, and adjustable means to control re-entry into the hammer path, as well as retention of the material for optimum results
- All Impactors are designed with the ability to add a means to provide attrition grinding to the reduction process, and in many cases, these optional features can be installed in the field to allow for future opportunities
- The use of wear liners throughout McLanahan Impactors emphasizes the maximum utilization of metal, interchangeable where practical, and consist of wear-resistant materials and alloys
- McLanahan Impact Crushers provide access for inspection and general maintenance with emphasis on visibility and safety
- Most McLanahan Impactors are designed with a means to hydraulically retract the hood for unencumbered access to the interior
- The rotor assemblies may be a three-bar, four-bar, or even five-bar design and are fabricated with a single rotor body, which is secured to the rotor shaft as a keyless assembly
- McLanahan Impactors are all designed with self-aligning, spherical roller bearings, mounted on a tapered shaft that extends on the drive side only to provide an unobstructed service platform on the non-drive side, and grease lubricated with labyrinth seals
- Hammers (blow bars) provide a protruding leading edge for maximum gradation control through the life of the hammers
- Hammers are available in a variety of alloys to better match the intended application
- The McLanahan line of Impact Crushers will provide a more cubical product with superior soundness by applying natural forces and allowing the material to fracture along all the weakest fissures, which allows you to increase productivity at the lowest cost of operation
Frequently Asked Questions
If I am trying to reduce my fines in a limestone quarry, should I use a Jaw Crusher instead of a Primary Impactor?
While it is true the Jaw Crusher will create less fines (say, minus 3/16”), it also creates more plus 1-1/2” material to be crushed downstream at the secondary and tertiary stages. Regardless of the type of crushers used downstream, the amount of fines generated in those closed circuit operations will actually be greater than any increase caused by a primary impactor.
How do the power consumption figures compare between Primary Impactors like the MaxCap and the VersaCap?
Since one employs an expansion chamber over the rotor and the other doesn’t, the MaxCap will perform at ½ hp per ton, while the VersaCap averages ¾ hp per ton. Electric motors will only draw as much power as the crusher needs. However, the theoretical difference in a 500,000-ton quarry or mine is about 90,000 kW/hours. That reflects only the primary crusher, not the added power it takes downstream to also recirculate 30% more rock through the secondary circuit.
Why do I see so many Impact Crushers in concrete recycling when the material is 100% abrasive?
Unlike sedimentary stone, e.g. limestone or sandstone, weathered concrete is very soft and friable. Most concrete pavement is less than 1,500 psi and pre-broken into slabs 2’ to 3’ square. Due to the friability, they shatter quickly into particles 3” and smaller on the initial pass through the impactor. The hammer wear life tends to be far shorter due to the abrasion, but recirculating loads are minimal for base material. In the case of a mobile contractor, single crusher systems are far more economical when relocating on a regular basis.
What is the main difference between the VersaCap P-Series and the R-series? Are they both primary impactors?
Yes, they are both primary impactors. In fact, the only real difference is the rotor assembly. The VersaCap P-Series is a primary impactor that accepts 30” boulders in quarried stone, and generates a nominal 6” minus. The VersaCap R-Series uses the same housing, but the rotor is designed specifically for large, highly-friable materials like concrete rubble. In the case of recycling concrete, the R-Series rotor is lighter in weight for portability, and the hammers are thinner, reducing the cost of spent hammers.
Under what circumstances should I consider automation for adjusting an Impactor?
The MaxCap Primary Impactor comes standard with fingertip control. While not fully automated, it is designed to integrate into any programmable logic controller based system. As for the other impactors, the vast majority of operations will be fine with a simple shim adjustment, which requires no automation. However, the semi-automatic system on the VersaCap and NGS Impactors essentially requires only an electrical control over the hydraulic system, which would be running during operation. Once you find the right setting, and plan to stay consistent, you can add shims, and shut off the hydraulic power unit. If you are anticipating the need to change settings on a regular basis, the full automation system with PLC and touch screen is available and capable of being integrated.