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Full text of "Metallurgy Of Cast Iron"

" BANKING*'   FURNACES   AND   CUPOLAS.             123
of a long runner, so that what flows out below the level of the tap-hole can be broken up. This plan is one adopted for "blowing-out" as well as " banking." As will be seen by Fig. 19, page 93, there are often very large bodies of metal below the tap -hole. Even by the plan just described these are rarely ever all drained from a furnace, always leaving some to solidify that will have to be brought back to a liquid state when the furnace is " blown in," requiring as a general thing but a few days.
The first move in preparing to "bank" a furnace is to discontinue 'its charges of ore and lime in the regular way and to admit chiefly fuel, in order to keep the furnace filled, occasionally dumping a little ore and lime to divide the fuel and to destroy the union of a solid combustible body of fuel and thereby . assist in smothering combustion. As soon as it is found that the last regular charge of ore, lime and coke has passed the level of the tuyeres, the furnace is tapped and an extra pressure of blast applied so as to force out all metal possible. This done, the blast is shut off and the '' banking '' operation commenced. When this is completed the furnace is filled up with fuel, etc., as above described, and in some cases the surface of the last charge is covered over with fine ore or loam sand to assist in shutting off draft, in which state the furnace is left standing. As a general thing, 'wherever sand can be used for banking, it is preferable to clay, as the latter is apt to-crack in drying and leave crevices whereby air can find access to the fire to excite combustion.
In some cases the fire may lie dormant in a good condition for six months or more without any renewalform Mr. Edgar S. Cook, 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     "