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IN OPEN-CUT quarry operations the loading of the blasted rock for transportation to the primary crusher house involves either power-shovels, or hand labor-and the latter has become practically extinct, at least as far as the American quarry is concerned. Any size of primary crusher may be used for hand-Ioaded rock; it all depends upon how much secondary shooting, and hand sledging, the operator feels he can afford. So-called "one-man" stone-that is, stone of a size that can be lifted into small cars or carts by the average laborer can be handled through a 10- or 13-in. gyratory crusher, or a jaw crusher of equivalent receiving opening. Usually, for hand-Ioading operations, capacity and product size govern the choice of the primary crusher. The unit labor cost of feeding hand-Ioaded stone is higher for small crushers than it is for larger machines but, if the labor market is such as to permit hand-Ioading in the quarry, a little additional labor at the crusher will not add materially to the cost of production.
In the American quarry, gravel pit, and open-cut mine, the power shovel, supplemented to a lesser extent by other types of excavating equipment, has, within the last forty years, practically eliminated hand loading. Today, in these
operations the power shovel is just as necessary as the crushing planto In any quarrying or open-pit mining operation the primary crusher, shovel, and transportation equipment should function as a team; therefore these three items of equipment, when possible, should be considered as complements of each other when making selections. This is especially important with respect to the crusher and the shovel. |
