Secondary Crushers For Aggregates
- Published: Thursday, 01 October 2009 08:00
Equipment manufacturers continue searching for ways to increase the throughput of their cone and impact crushers. Increasingly, however, flexibility is becoming a more powerful selling point for OEMs, as operators seek faster ways to change plant configurations or even relocate. Maintenance also is of growing importance, and OEMs are responding with easier access points for critical component adjustments. Quality remains paramount, and manufacturers are finding creative ways to upgrade plant designs for better particle shape.
OEMS MARKET MAINTENANCE AND PRODUCTION
Telsmith's range of horizontal-shaft impact crushers typically are applied as secondary crushers in aggregate or concrete-recycling applications and processing recycled asphalt. There are seven sizes ranging from the smaller 50-horsepower model 2421 up to the 400-horsepower model 5263. All models incorporate open-disc rotors for material penetration, hydraulically opened upper frame yielding vertical access to the rotor and aprons for maintenance, fully lined housing, inspection doors and quick-adjust aprons. They are available as standalone units or incorporated into portable plant configurations.
Telsmith's SBX cone crusher has new internal components and crushing chamber profiles, which works for coarse secondary crushing applications. The company says it now accepts larger stone than previous models. It features hydraulic anti-spin and remote dynamic adjust systems, as well as digital sensors. The SBX is equipped for adaptation into automated crusher control systems. Telsmith also provides the optional TRAC 10, a stand-alone crusher control system, which delivers all the benefits of crusher automation without the big budget hassles of completely reworking plant controls. The SBX cone crusher series is available in three models ó the 44SBX (300 horsepower); 52SBX (400 horsepower); and the 57SBX (500 horsepower).
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The UltraMax impactor from Eagle combines primary and secondary crushing into one unit. The models are available with feed openings as large as 69 ◊ 42 inches or as small as 27 ◊ 32 inches. The largest model (60,200 pounds), UM69, requires 400 to 600 horsepower, while the smallest unit (16,600 pounds), UM04, requires 60 to 100 horsepower. It has a solid steel, three-bar rotor. The crusher has a gravity-hung, reversible manganese primary curtain and a hydraulically adjustable secondary curtain with bolt-on replaceable liners. The UM69 can be mounted stationary or on a skid for transport. When combined with 6- ◊ 20-foot screens, the UM69's high reduction ratio (24-1) produces uniform, cubical Superpave products, the company says. UltraChrome titanium blow bars can be added to reduce wear costs to as low as $0.07 per ton in applications ranging from hard rock to heavily reinforced concrete.
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The Grand Slam horizontal-shaft impactors from Stedman use high-chrome metallurgy to stand up against limestone, gravel and asphalt. There are 11 models with capacities ranging from 5 to 1,200 tons per hour. The impactor design incorporates both primary and secondary aprons, eliminating the need for grate bars and discharge screens. A two-stage crushing action produces reduction ratios up to 30 to 1.
A full-length rotor shaft with two double-row, spherical-type bearing assemblies has a taper-lock design for strength. The rotor features either a two-, three or four-row design, depending on model size. A wedge-locking design secures the breaker bars and simplifies breaker bar servicing. High-chrome breaker bars can be rotated many times before replacement. A rotor lock table facilitates breaker bar rotation and replacement. Front- or rear-opening housings allow access to crusher chambers.
Both the primary apron, where initial size reduction occurs, and secondary apron, where final reduction takes place, are lined with interchangeable 3-inch-thick, tapered liners. Gap adjustments for both aprons can be set from the external housing. An optional spring bridge assembly provides additional force to maintain gap settings yet allows for retraction of the apron under extreme loads and immediately returns to original setting. Two-inch-thick, high-chrome side liners come in three different shapes ó triangular, rectangular and square ó and are interchangeable from model to model.
Options include a Crush Plus Grinding Path System, which creates a third crushing chamber to maximize one-pass product yield; an automated apron adjustment system that maintains the gap settings for aprons and the grinding path; apron heaters that are installed on the feed chute and primary and secondary aprons to minimize buildup when reducing wet and sticky materials; and an air cannon that discharges a blast of air into the crushing chamber to dislodge dry material buildup.
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Jeffrey Rader Corp.'s Centroload Feeder feeds cone crushers and vertical-shaft impactors evenly around the circumference of the crusher opening. This can replace standard pan feeders with radial discharge units, which is an obstruction during maintenance. The unit incorporates many of the features of a standard Jeffrey Radar Feeder such as precompressed springs, standard motor and eccentric shaft drive arrangement. Material travels around and into a feed spout at the discharge end of the feeder.
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Nordberg NP series impact crushers have a heavy-duty design, wear materials and crushing chamber design. Hammers are fixed to rotors by a single wedge assembly for tightening torque. Hammer alignment on rotor contact faces helps eliminate gaps between the rotor and the hammers. The same hydraulic power unit opens the frame and adjusts the liners. Protected doors located all around the frame make it possible to reach the interior of the crusher. Hammers can be changed vertically or horizontally. Sensors on the frame prevent startups during maintenance.
The unit has optional hydraulic assistance, hydraulic adjustment, third breaker plate and different grades of wear-resistant steel for hammers, liners and side liners. An optional automatic setting allows the operator to change the setting of the impact crusher from a distance. The higher breaker plate is automatically set to a calculated value, depending on the setting of the lower breaker plate and the feed size.
The largest of the NP series is the NP2030, which has a 91- ◊ 75.6-inch feed opening. Maximum feed size is 59 inches. It has 1,200 horsepower and can operate at 520 rpm. The complete crusher weighs 177,000 pounds and has a 78.7-inch-diameter rotor.
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