Crushers impact

Impact crusher Impact isolating class Impact mills Impact polystyrene (IPS)... 

Mech nic l Impact Mills. The mechanical types include cmshers, hammer mills, pin disk mills, turbine mills, and mills with air classifiers. Impact Crusher. Feed material is introduced through a feed opening onto a rotor moving at between 25 and 50 m/s (Fig. 11). The initial impact by the rotor causes some size reduction, and the material is accelerated up to the speed of the rotor and flung against the impact plates, where further size reduction occurs. It is possible to wear-protect these units quite well, so that abrasive materials can be handled. The final end particle size can be varied by the inclusion of an outlet grid to vary the residence time in the machine. 

Smooth jaws produce more numerous flaky pieces than corrugated jaws. Curved jaws produce less fines but more numerous flaky particles. Crusher speed has little effect. The presence of material too small to be crushed has a deleterious effect on the shape of products. Secondary crushers with a small reduction ratio can improve the shape of primaiy crushed material, but secondaiy crushers are not inherently different from primaiy crushers. Slotted screens can remove flaky particles from the product. Impact crushers produce fewer flaky particles than any other type. 

Co), American Ring (American Pulverizer Co), Steelman Type B Heavy-Duty (Stedman s Foundry Machine Works), and Joy-Hazemag Impact Crusher (Joy Mfg)... 

Ore beneficiation consists of two main steps comminution and concentration. Comminution is first performed by crushing. Equipment in use comprises jaw, cone, or impact crushers working mostly in closed circuits with vibratory screens. The second step in comminution is grinding, which is undertaken in rod or ball mills working in closed circuits with classifiers. 

Jaw crusher feed diameter 0.1 to 1.5 m reduction ratio 5 1 to 10 1 capacity 1 to 300 kg/s Mohs hardness <9 (reduction by compression). Gyratory crusher feed diameter 0.75 to 1.5 m reduction ratio 5 1 to 10 1, usually 8 1 capacity 140 to 1,000 kg/s Mohs hardness <9. More suitable for slabby feeds than jaw crusher (reduction by compression). Roll crusher feed diameter 1 cm reduction ratio 5 1 to 10 1 capacity 0.3 to 20 kg/s Mohs hardness <7.5. Suitable for softer, friable, and nonabrasive materials. OK for wet and sticky materials. Cone crusher and short head cone feed diameter <25 cm reduction ratio 5 1 to 10 1, usually 7 1 capacity 5 to 300 kg/s Mohs hardness <8. Usually secondary or tertiary crusher. Impact crusher pulverizers, shredders, or smooth roll feed diameter 1 cm with a reduction ratio of 7 1 to 10 1 capacity 0.3 to 50 kg/s. Mills, hammer, feed diameter 10 mm, reduction ratio 10 1 to 50 1, capacity 0.01 to 5 kg/s Mohs hardness <4.5. Maximum fines feed not hard or abrasive. Mills, ball, and rod feed diameter 0.5 mm with a reduction ratio of 10 1 to 50 1 Mohs hardness <9. Mills, autogenous, semiautogenous feed diameter 200 mm, reduction ratio 10 1 to 50 1 capacity 0.1 to 100 kg/s Mohs hardness <6. Mills, fluid energy feed diameter 50 pm reduction ratio 10 1 to 50 1 capacity <2 kg/s Mohs hardness <4.5. 

Impact Crushers One type of impact crusher is the hammer mill. This consists of swinging hammers rotating at high speed on either a vertical or horizontal axis inside of a lined crushing chamber. Ore is broken by impact with the hammers and breakage plates that reside on the periphery of the crusher. Reduction ratios as high as 40 1 can be obtained however, because of their very high reduction ratios, they have a tendency to produce more fines than other crushers. 

Hammer Mills. One of the most versatile, economical, and widely used impact mills is the hammer mill (Fig. 12). Many variations are produced, with special types available for specialized applications, eg, quick screen change for animal feed, heavy duty for minerals, and light constructions for woodchip. The principle employed is similar to that of the impact crusher however, the rotation speed can vary from 20 up to 100 m/s with high speed fine-grinding versions. The oudet screen is used to vary the residence time, which in turn affects final particle size. The size of the end product is an order of magnitude finer than the size of the perforations in the oudet screen. 

Metal / nonmetal N onmetal / nonmetal crusher, cutting mill, impact crusher... 

In most operations, crushers are selected with care to produce the required amounts of aggregate-sized particles, without over-production of fines (below 3 mm and including dust). Where large amounts of fines are required, impact crushers are often used. When impactors cannot produce the required fineness, it becomes necessary to grind the limestone. 

Figure 5.4. Cross-section of an impact crusher (by courtesy of Hausherr UK Ltd. and Hazemag EPR GmbH)...

Pulverised limestone may be produced economically in impact crushers, such as hammer and beater mills. For use in agriculture, the product should be at least 95 % less than 3.35 mm and substantially less than 600 pm (see chapter 10). 

Blow-bar is the wear surface attached to the rotor of an impact crusher. 

Impact crusher pulverizers, shredders or smooth roll feed diameter 1 cm with a reduction ratio of 7 1 to 10 1 capacity 0.3 to 50 kg/s. 

For more brittle materials, consider an impact crusher provided very abrasive (such as silica) or sticky materials (such as day) are not present. 

There are two types of impact crushers horizontal shaft impactor and vertical shaft impactor. 

The roll crusher parameters are important, in particular the rotational speed, size, and shape of the crusher teeth. Usually the mills are fitted with variable speed drives. The discharge from the compression (roIQ crusher is controBed by the gap setting. Evaluation of circuits using roll crushers indicates h her fields than from those eqiipped with impact crushers. 

The impact crusher is best suited for dealing with brittle hard to medium-hard material with natural cleavage planes. It cannot cope very well with soft, plastic and moist material. 

Depending on the hardness and size of the feed, coarse impact crushers reduce the material to a product size of between 150 and 200 mm and attain reduction ratios of between 6 1 and 20 1. The circumferential velocity of the rotor is a major factor low velocity results in a coarse product with higher velocity the size reduction... 

Steel apron conveyors or chain conveyors, though mechanically more elaborate and expensive than belt conveyors, are preferable for product removal from impact crushers and from hammer crushers not equipped with bottom grids. The reason is that the material discharged from the crusher falls with greater impact force on the conveyor than when a bottom grid limits the size and impact velocity of the pieces discharged. 

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