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124 METALLURGY OF CAST IRON.
of fuel, but this is seldom done. If, after three or six months of banking, it is found that conditions of trade, etc., will not demand '' blowing in,'' as anticipated when first banking the furnace, the fires will often be allowed to die out, in order to make preparations for "shoveling out," so as to discover if a furnace requires re-lining in parts or as a whole.
A good illustration of the extent to which banking a furnace may be carried is that conducted under the able management of Mr. C. I. Rader, during the years 1893-95, at "the Paxton Furnace, Harrisburgh, Pa. Furnace No. i at this place was banked'August, 1893, and not opened until June, 1895, a period of one year and ten months, at which time the furnace was found in a condition to be successfully * * blown in.'' Mr. Rader says a light ore burden and half coke and anthracite were used in banking down the furnace, and the top covered with a layer of fine ore. This is the longest period of successful *'banking" of which the author has any record.
When " blowing in " a " banked furnace," the first operation is to clean out the tuyere holes, etc., of their clay and sand packing, after which the refuse and dead ash in the furnace are pulled and shoveled out through the tuyere openings and slag holes, so far as possible. This done, the tuyeres are replaced and their water and blast connections completed. A heavy bed of fuel is now charged, after which charges of ore, lime and fuel are delivered into the furnace. The burden of ore and lime is gradually increased in weight in the first charges until several are delivered, when the regular burden is then charged on. The blast being on, the furnace is again in condition to make iron. For theok, president of the Warwick Iron Co. of Pottstown, Pa. is often surprising how rapidly, as about 75 per cent of the heat generated from the solid fuel is utilized. This is attained where one ton of coke will produce one ton of iron; and Sir........................ 2,720 "