Bulletin . 86 FELDSPARS OF NEW ENGLAND AND NORTH APPALACHIAN STATES. the mills be inclosed in dust-tight coverings. No such precautionsare taken, however, and only in a few instances is any attempt madeto box the mills in order to prevent the escape of the feldspar dust,which is the most valuable part of the product. The ground feldsparis generally shoveled into carts or wheelbarrows and removed to thestock bins or loaded directly into box cars for shipment. TUBE MILLS. Tube mills (fig. 18) are probably the most economical and in manyrespects the most efficient machine available for feldspar p
Bulletin . 86 FELDSPARS OF NEW ENGLAND AND NORTH APPALACHIAN STATES. the mills be inclosed in dust-tight coverings. No such precautionsare taken, however, and only in a few instances is any attempt madeto box the mills in order to prevent the escape of the feldspar dust,which is the most valuable part of the product. The ground feldsparis generally shoveled into carts or wheelbarrows and removed to thestock bins or loaded directly into box cars for shipment. TUBE MILLS. Tube mills (fig. 18) are probably the most economical and in manyrespects the most efficient machine available for feldspar are long steel cylinders with heavy cast-iron heads, and are oftwo types—namely, axial supported/ in which the mill revolveson two hollow steel trunnions, and roller supported, in which thecyUnder is fitted with a broad flat tire about its circumference nearone end and a cog-faced tire near the other end. The machine restson rollers and cogwheels, which provide the power for revolving the. Figure 18.—Tube mill. cylinder. The tube mill is lined, like the ball mill, with silex or porce-lain blocks, and is charged with flint pebbles. The cylinder is set ona slight slope, so that the sand fed into it at the high end works itsway down and out at the opposite end, being pulverized on the feldspar is fed continuously to the mill through an opening in thecenter of the axle, and when it reaches the opposite end it passes outthrough the center of the axle at that end. In some mills the outletis by small holes in the periphery of the mill. The number of revolu-tions which the material makes between entrance and exit and hencethe fineness to which it is ground depends upon the slope of the quantity of pebble charge and the rate at which the material is fedto the mill are also factors that require attention, especially in thecenter discharge type. Too heavy feed forces the semiground materialforward and out of the mill before it is properly pulverized, w
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectminesandmineralresou
