"BANKING FURNACES AND CUPOLAS. 125
first two " casts ".or day's run a furnace is liable to work cold, which results in giving a low-grade metal or iron high in sulphur and low in silicon. As a general thing, furnaces are compelled to use cold blast when '' blowing in,'' for the reason that there is no "gas to make the hot blast ovens operative until after a furnace becomes sufficiently heated to have gas pass down the "down-comer" to the ovens. A few plants, like that of the Carnegie Steel Co., having several furnaces connected or in close vicinity, can bring hot blast from other furnaces until the "blown in" furnace gets under way. Where cold blast has to be used at the start, it takes much longer to get a high-grade iron than where hot blast can be obtained. With hot blast they may often, at the very first ' * cast,'' secure high grade iron, whereas with cold blast it may take a dozen "casts" or more to do so, and in either case, the largest output is not generally obtained until a furnace has been in blast from one to three months.
Those founders inexperienced in furnace work can well imagine from the description here cited that although "banking" is a compromise to "blowing out,'' which means a complete shut-down, the furnace manager is desirous of avoiding such manipulations so far as possible, as the expense is by no means light, and many sacrifices will generally be made in having capital lying idle in piles of pig iron in order to run a furnace steadily, rather than " banking " to await increase of orders or a demand for their product. If furnacemen have any assurance that they will not " blow in " after three months' " banking," they will generally "blow out," as the accumulation of ash and dirt from a furnace banked to exceed three months 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 "