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Practically all that we have had to say about the application of the single-roll crusher will apply as well to the Edison roll crusher. It is better adapted to handling blocky stone than is the single-roll machine, because its slugging action is much more vigorous, and it will handle any material that will not build up on the sides of the vertical hopper. It is not as simple a machine to feed as the single-roll crusher, because its narrow hopper necessitates the uses of skips, or very short-bodied cars. A heavy-duty apron feeder would of course solve this problem, but so far as we know, none of these crushers were so equipped.
The very high peak capacity of the crusher constitutes something of a problem in plants of medium capacity.
It is not economically feasible to provide elevating or conveying equipment to handle peak loads of around 4000 t P h in a plant designed to turn out that much stone in an 8- or 10-hr day; consequently means must be provided to smooth out these high surge loads.
This can be taken care of by a surge bin and feeder below the crusher, or by passing the roll product direct to a secondary crusher of uniform-capacity
characteristic. A feeder ahead of the rolls would smooth out peaks on mixed feed but. once a 10- or 12-ton block of stone is dropped into the crusher, that quantity comes through very quickly as crushed stone, which would render the regulating properties of the feeder of questionable value.
Modified forms of this crusher were used by Mr. Edison for secondary and tertiary stages. The crushing equipment in one large plant, for example, comprised a set of 6- x 7-ft rolls (8-in. product), a set of 4- x 4-ft secondary rolls (31h-in. product), and a set of 4- x 3-ft tertiary rolls (1 ½ - in product), these last rolls being in closed circuit These smaller machines were also run at high speeds, their surface velocities being slightly over 3000 ft. per min.
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