Crushers types

Continuous-type buckets (Fig. 21-5/) are generally back-mounted to chain or belt at close intervals. They are usually fabricated of steel. Style 5 is standard for normal materi s, with style 6 a low-front type for better discharge of difficult materials. Style 7 buckets are used for additional capacity or large lumps, and style 8 for inclined crusher-type elevators. Style 9 bu( ets are designed for extremely high capacities and are usually side-mounted and hinged together. 

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. 

The feed-preparation screen between crusher and separately vessel may be of either the revolving or the vibrating type. Wash water is apphed only to the feed end ofthe screen so that the process feed will enter the separator moist but without any free water, which would lower pulp density. In a few instances it has been found advantageous to provide for surge storage between screen and separator to drain off further excess water. 

Many authors have assumed that breakage occurs preferentially along grain boundaries, but there is scant evidence for this. On the contraiy, Gorski [Bull. Acad. Pol. Sci. Ser Sci. Tech., 20(12), 929 (1972) CA 79, 20828k], from analysis of microscope sections, finds an intercrystalhne character of comminution of dolomite regardless of the type of crusher used. 

The overhead eccentric jaw crusher Nordberg, Telsmith Jnc., and Cedarapids) falls into the second type. These are single-toggle machines. The lower end of the jaw is pulled back against the toggle by a tension rod and spring. 

The three general types of gyratoiy crusher are the suspended-spindle, the supported-spindle, and the fixed-spindle types. Pri-maiy gyratories are designated by the size of feed opening, and... 

Crusher Product Sizes Table 20-10 relates product size to the discharge setting of the crusher in terms of the percent smaller than that size in the product. Size-distribution curves differ for various types of materials crushed, and a general set of curves is not vahd. 

Primary gyratories will accept feed directly from truck or railcar. Most manuracturers make both mechanical and hydraulically supported types. Figure 20-23 shows a Nordberg primaiy gyratoiy crusher with spider suspension. It is available in 1- to 1.5-m (42-, 48-, 54-, and 60-in) feed sizes. Table 20-11 gives capacity data for the Superior gyratoiy crusher (Allis-Chalmers). 

In the second type of mill (Fig. 20-28), a cyhndrical grating is provided beneath the rotor for product discharge. Some hammer crushers are symmetrically designed so that the direction of rotation can be reversed to distribute wear evenly on the hammer and breaker plates. When such a Pennsylvania nonreversible hammermill is used for reduction, material is broken first by impacl against hammers and then by rubbing action (attrition) against screen bars. Performance data of Pennsylvania reversible hammer mills are shown in Table 20-14. 

Penn.sylvania Cru.sher Corp. offers a variety of impactor types granulators, Bradford breakers, roll crushers, and jaw crushers. (See Table 20-15.)... 

The Wilhams ring-roller mill Williams Patent Crusher Pulverizer Co.) is an air-swept mill with integral classifier of the rotating-blade type (the Spinner air classifier) or a double-cone type. The fluid-bed roller mill system has jets to introduce hot air into the bed of coal in the mill to diy it. 

Crushed Stone and Aggregate In-pit crushing is increasingly being used to reduce the rock to a size that can be handled by a conveyor system. In quarries with a long, steep haul, conveyors may be more economic than trucks. The primaiy crusher is located near the quariy face, where it can be suppRed by shovels, front-end loaders or trucks. The crusher may be fully mobile or semimobile. It can be of any type listed below. The choices depend on individual quariy economics, and are described by Faiilkner [Quairy Management and Products, 7 6), 159-168 (1980)]. 

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. 

If the rock is abrasive, the first stage of crushing may use gyratory or jaw crushers, otherwise a rotor-impact mill. Their reduction ratio is only 1 12 to 1 18, so they often must be followed by a hammer mill, or they can feed a roll press. Rotor crushers have become the dominant primaiy crusher for cement plants because of the characteristics. All of these types of crushers may be installed in moveable crusher plants. 

Hydraulic piston-type compactors for collection vehicles, on-site compactors, and transfer-station compactors roll crushers used to fracture brittle materials and to crush tin and aluminum cans and other ductile materials... 

The production of aluminum begins with the mining and beneficiation of bauxite. At the mine (usually of the surface type), bauxite ore is removed to a crusher. The crushed ore is then screened and stockpiled, ready for delivery to an alumina plant. In some cases, ore is upgraded by beneficiation (washing, size classification, and separation of liquids and solids) to remove unwanted materials such as clay and silica. 

The simplest industrial screening equipment are stationary screens, over which the material to be screened flows. Typical of this type are Grizzly screens, which consist of rows of equally spaced parallel bars, and which are used to scalp off over-sized rocks in the feed to crushers. 

In an investigation by the U.S. Bureau of Mines1141, in which a drop weight type of crusher was used, it was found that the increase in surface was directly proportional to the input of energy and that the rate of application of the load was an important factor. 

The apparent efficiency of the size reduction operation depends on the type of equipment used. Thus, for instance, a ball mill is rather less efficient than a drop weight type of crusher because of the ineffective collisions that take place in the ball mill. 

Ddtermination des pressions en vase close) 83-90 (Mesure de la pression a brief description of la bombe type Vieille, bombe Krupp, crusher et quarz piezodlec-trique) 17a) M.A. Cook, JChemPhys 15, 518-24(1947) (Some calcd values of Chapman-Jouguet pressures and temperatures) 18) Yu.N. Riabinin (or Ryabinin), DoklAkadN 58, 245-48(1947) CA 44, 7539 (1950) (Influence of pressure on the rate of thermal decompn of expls) (Abbreviated translation by B.T. Fedoroff is available in PicArsn Library as U 6383) 19) Stett-... 

The 60/40 mixt was cast-loaded to a density of 1.65 its mp 65-70°, Expln Temp 264° higher Brisance, by Copper Cylinder Crusher Test 100% (PA=100%) Power by Ballistic Mortar 96% (PA=100) Deton Velocity by Dautriche Method 7050m/sec Impact Sensitivity with 15kg Weight 14cm (max wt for no expins) Friction Sensitivity 60kg (max pressure betw two rubbing surfaces for no explns). Used, under the name Type 98, in Navy Bombs,... 

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