Impact Crushers - Secondary

The NGS Impact Crusher is extremely versatile. The most common application involves taking primary-run limestone from either a Jaw Crusher or impact breaker and reducing it into a construction grade aggregate. However, with the optional third curtain assembly, it is possible to increase the amount of chip stone for asphalt and some concrete mixes.


The NGS Impactor represents the next generation secondary Impact Crusher. Still unmatched in the industry, the NGS Impactor is engineered to bring more profitability to aggregate and mineral processing operations. Developed to mimic the productivity of its predecessor, the Impact II, this impactor generates a better, highly cubical product while reducing operating expenses. 

The NGS Impactor reduces downtime for adjustments, requires fewer wear parts to inventory and can be modified in the field to accommodate changes in the application and product requirements. The NGS Impactor is available in seven different model sizes, and each is uniquely designed with a means to retrofit most any Andreas-style Impactor at minimal cost. Optional features are available to enhance the simplified curtain adjustment to involve adjust-on-the-fly or advanced touchscreen automation capability. Combining 35 years of field experience with the latest technology available, McLanahan continues to expand the features of the NGS Impactor. 

Why McLanahan NGS Impact Crushers

McLanahan Corporation has a long and prosperous history in the mineral processing industries. We offer crushing solutions for soft materials like coal and hard and abrasive materials like granite or basalt.  Not only does McLanahan 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 avenue.

The NGS Impact Crusher commonly takes primary-run limestone from either a Jaw Crusher or impact breaker and reduces it into a construction grade aggregate. The optional third curtain assembly makes it possible to increase the amount of chip stone for asphalt and some concrete mixes. The adjustability in the curtains, at various rotor speeds, generates output gradations that can be manipulated in many ways. The NGS Impactor is equipped with wear resistant liners and hammers cast from various chromium alloys. Even applications in tough river gravel and abrasive concrete rubble tend to be profitable with the NGS Impactor. The rotor speed and the right hammer alloy opens a wide opportunity for material reduction in industries where new markets are growing. If your operation could benefit from higher reduction ratios while generating a cubical product with superior soundness, consider the NGS Impact Crusher. 

McLanahan offers the largest selection of Impact Crushers in the country. We have Impactors that have been in operation for more than 50 years and have earned a reputation of providing reliable equipment with unmatched service and support in the mining and aggregates industries. Choosing an NGS Impactor for your operation enables us to prove, once again, our dedication to the industry and to your success.

How NGS Impact Crushers Work

The NGS Impact Crusher is an Andreas-style impactor with basic features like disc rotors, reversible hammers, common wear liners, and hydraulic hood for access. However, the NGS advantage begins with the material flowing down a feed chute at an optimal angle. The feed chute allows the material to enter the rotor circle at a precise point where the hammers have the greatest affect in shattering the rock. The geometry of the primary curtain contains the initial spray of shattered rock and diverts the rock back into the hammer circle. The secondary curtain then receives a similar spray of finer particles as the material works its way around the rotor, coming into contact repeatedly with the hammers. 

A dual curtain impactor typically provides a 10:1 reduction in a limestone material. The NGS Impact Crusher offers the option of a third curtain, which in some applications may provide more than a 20:1 reduction. As with all Universal impactors, the NGS Impact Crusher provides a greater level of control over the flow of the material through the reduction process. The hammer profile in the NGS is an S-shape, which provides a protruding leading edge. As the hammer wears down, it continues to strike the stone with a sharp edge. This keeps the material flow more centered on the curtains. As the hammers wear, the gap between the hammer tip and the curtains becomes greater. Measuring from the bottom edge of the curtain, when the gap expands with every 1” of hammer wear, the resulting output gradation will become noticeably coarser.

The NGS Impact Crusher is extremely easy to adjust, no heavy wrenches or cheater bars needed. All it takes is a simple pull on the hydraulic lever. Then, lift the shims from the cradle, secure them in the shim pack with a thumb-screw, and let off the hydraulic cylinder. Check the gap through the inspection door, and you're done.

When the hammers are spent, the replacement process is quick and easy. A rotor lock and special lifting tool is included with every NGS Impactor as a safety-first initiative. Once the new hammers are in place, reset the curtain gaps, and the crusher is ready. 

With any Impact Crusher, it is always important to check for loose hardware. We are proud of the fact that our NGS line of crushers have the largest inspection and maintenance doors of any secondary impactor on the market. Access is critical. Providing more visibility empowers operators to be more proactive. McLanahan now offers the NGS Impactor with the ability to be adjusted while under full load. Watch the discharge conveyor, and allow the rock to grow or shrink with the touch of a finger.

Want even more control? We offer a complete automation program with touchscreen to adjust the gap settings either for hammer wear or ever-changing product demands. This full automation feature also includes hands-free calibration capability. Just give the command and let the crusher adjust accordingly. 

Frequently Asked Questions About Secondary Impact Crushers

Ask An Expert

The primary curtain is generally set at a measurement equal to one-half the top size of the feed material. The secondary curtain is then set at or near the desired top size of the product. If in closed circuit, adjust the second curtain to limit the return load to less than 15% of the new feed. Check the vibration of the two curtains and adjust the primary curtain to equalize the vibration between the two curtains.

The third curtain is below the center line of the rotor, which means it will involve attrition and grinding to affect the reduction. That will add wear cost to the operation. If the future plans for the crusher limit it to products greater than ¾”, forego the option because the dual curtain arrangement will be sufficient. However, if product sizes smaller than ¾” are desirable, the third curtain may be sufficient to eliminate a tertiary crusher in the system.

The NGS Impact Crusher is very easy to adjust with simple hydraulic shim adjustment. Our fully automated system is considerably less expensive than competitive units, but if you’re adjusting for wear or product changes on a rare occasion, the standard system is all you need.

Unlike our competitors, we offer another alternative. If you move from one quarry to another, or your feed material is inconsistent, the semi-automatic adjust feature is both affordable and easy to use. This will provide adjust-on-the-fly capability, which can complement a shim adjust arrangement. 

The NGS Impact Crusher generates a better, highly cubical product while reducing operating expenses.

Features & Benefits
  • Two independent gravity hung impact curtains, both suspended from the same pivot point, provide unmatched ability to hold gap settings against surges in material flow
  • A third curtain, when needed, can be added to the Impactor as a field kit in the event future opportunities arise, and once installed, can be fully retracted to function as a deflector plate
  • The impact curtains are equipped with interchangeable cast liners of chromium alloy, bolted into place and available in half sizes for easier handling
  • Optional fabricated liners are available for most models and stretch the full width of the curtain, and they can be used in various positions throughout the Impactor
  • The impact curtains are equipped, as standard, with hydraulic assisted shim adjustment, and are engineered to provide quick and simple replacement when necessary
  • To access the interior of the crusher, the housing hydraulically opens with the hood retracting beyond the center of gravity, engaging a mechanical hood lock for added safety
  • A rotor lock inserts into the rotor of a positive means to keep the rotor from turning during maintenance
  • The rotor assembly can be a three-bar, four-bar, or even five bar design
  • Hammers are held into the rotor with easy-to-remove-and-install L-blocks that reduce downtime and provide a positive means to retain the hammers during operation
  • Large access doors on the top, back and sides of the Impactor provide unmatched access to the interior of the crusher for inspection and maintenance
  • Rotor assembly features a rotor weldment, secured to the shaft with a keyless assembly and mounted on spherical roller bearings

Need Some Help?

Our customer service team is here to help you 24/7. We can ship you parts, send field service technicians to your site and answer any questions you have. Whatever you need, we are here for you.