Crushers toothed

Primaiy crushers used are jaw, gyratoiy, impact, and toothed roll crushers. Impact mills are hmited to hmestone and softer stone. With rocks containing more than 5 percent quartz, maintenance of hammers may become prohibitive. Gyratoiy and cone crushers dominate the field for secondaiy crushing of hard and tough stone. Rod mills have been employed to manufacture stone sand when natural sands are not available. 

Roll crushers are made either smooth or with teeth. A 24 in. toothed roll can accept lumps 14 in. dia. Smooth roiis effect reduction ratios up to about 4. Speeds are 50-900 rpm. Capacity is about 25% of the maximum corresponding to a continuous ribbon of materiai passing through the roiis. 

The single roll crusher shown in Figure 2.13 consists of a toothed crushing roll which rotates close to a breaker plate. Figure 2.14 is an illustration of an industrial model. The material is crushed by compression and shearing between the two surfaces. It is used extensively for crushing coal. 

The material aggregate is fed from the mixer via a connecting shaft to the cooler (5) and then to the crusher (6) wherein it is crushed preliminarily (by a single-roll crusher unit) and finally (by a toothed-disc mill). 

Roll crushers are available as smooth or toothed rolls. Figure 12.6(b) is an example of a smooth-roll crusher and Table 12.10(b) presents data for a double tooth-roll crusher for coal. For smooth rolls, the feed size is hmited by the angle of nip, which depends on surface conditions but it is approximately 16 degrees. Table 12.10(c) contains additional operating data for roll crushers. The relation between the diameters of the roll d, and feed df and the gap do between the rolls is given by... 

These tertiary crushers employ smooth or toothed heavy-duty impact and abrasion-resistant steel-rimmed rolls. The rolls are mounted inline in a horizontal manner and turn toward each other at equal speeds to create a nip into which a friable feed material is introduced (Fig. 4). Heavy-duty compression springs with automatic reset are used to dampen crushing shock and to protect the crusher from tramp iron and oversize material. An adjustable screw that adjusts spring tension changes the crusher opening. A flywheel is used to even out pulses and economize on power consumption. These crushers have a theoretical maximum reduction ratio of 4 1 and will only crush materials to about 10 mesh. Roll crushers produce a controlled product size distribution without a lot of fines. The narrow particle size distribution is achieved by controlling a combination of variables including roll speed, gap measure, differential speed, feed rate, and roll surface. 

Toothed single roll crushers that crush materials by working on a breaker plate are also available. The crushing teeth are set in segments to facilitate replacement. 

BatteUe personnel contacted manufacturers and vendors of these types of crushers to determine the applicability of the equipment types to the specific requirements for the explosives-contaminated debris. Toothed-roll crushers would be unable to achieve the required size reduction. This type of equipment was not recommended by the manufacturers and/or vendors. 

Crushers are slow-speed machines for coarse reduction of large quantities of solids. The main types are jaw crushers, gyratory crushers, smooth-roll crushers, and toothed-roU crushers. The first three operate by compression and can break large lumps of very hard materials, as in the primary and secondary reduction of rocks and ores. Toothed-roll crushers tear the feed apart as well as crushing it they handle softer feeds like coal, bone, and soft shale. 

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