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The single-roll crusher, as compared to the gyratory and jaw types, has a rather limited field of application, and being a "specialist" it is only fitting that it should be exceptionally proficient in the field for which it is adapted. It is a highly effective primary breaker for such material s as the soft-to-medium limestones, dolomite, magnesite, phosphate rock, cement rock and shales. It is decidedly not a hard-rock crusher, nor is it suited for rock of massive or blocky structure unless it is, at the same time, of friable texture. Practice is to limit its application to rock having a crushing strength not exceeding 15,000 p s i.
During the crushing process, particularly when material is riding on the roll, there is considerable slip or rubbing action between the material and the tops of the teeth, and this will obviously result in rapid wear if the rock is at all abrasive. For that reason this crusher is not economically suited to the handling of rock containing more than a few percent of free silica-unless, again, it. is very soft and friable.
By virtue of its positive discharge characteristic the single-roll crusher ranks as a top performer in the handling of wet and sticky material, and it will take care of stone containing a substantial admixture of loam or clay. In this respect we would rate the currently, leading types of primary breakers in the following order:
- Single-roll crusher
- Jaw crusher
- Gyratory crusher
Some very soft materials-fuller's earth, for example-do not handle well in the single-roll crusher, clinging to the anvil and refusing to work down into contact with the teeth. Clay and similar sticky material will of Course behave in the same manner, but if there are enough pieces of solid rock in the load, the machine will keep itself clean by using the rock as a scouring agent.
Because it is a proficient self-feeder the Fairmount crusher may be fed directly from cars or trucks; discharging into a plate steel super-hopper of suitable proportions, this hopper being superimposed on the heavy cast hopper which is a part of the machine. If the loads are not too large with respect to the size of the crusher, the entire load may be dumped at once, without much risk of bridging. For very large cars or trucks controlled dumping is preferable.
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