Page:Encyclopædia Britannica, Ninth Edition, v. 13.djvu/347

IKON 331 Numerous other machines 1 are in use for various special purposes, such as wire-drawing, drilling, screw-tapping, &c. ; the description of these would take up more space than can be given here. A marked feature in most American iron-works is the general handy, compact, and efficient nature of the machinery of all kinds, and the use of various physical-exertion-saving contrivances and arrangements for ventilation and cooling of workshops, &c., many of which appliances are not so frequently to be met with on the eastern side of the Atlantic, more especially in England. The general arrangement and planning out of works, moreover, is usually far superior to that of the older British works, which have gradually grown to their present dimensions, and consequently have not been systematically laid out as a whole. In consequence of attention to such details as these, the output of finished material from a given amount of plant is frequently considerably greater in America than would be attained in other countries, whilst the labour required is not proportionately increased ; thus the largest makes of Bessemer metal from a given converter ever registered have been attained in American works ; and so in other instances. To a considerable extent the same remarks apply to Continental establishments, at any rate to many of those of more modern arrangement ; of late years, however, the spirit of competition and other influences have rendered it imperative upon the British ironmaster to pay more re gard to such matters than was formerly the case, and to adopt many American and Continental improvements in details, experience | having opened his eyes to the fact that it is possible for other nations, though less naturally favoured as to ores and fuel, to compete successfully with him, and undersell him, not only as to foreign trade, but even in the case of English contracts for iron work for home use. The reheating furnaces employed to heat up to a welding temperature the piles intended to be rolled are essentially low reverberatories, much resembling puddling furnaces, in which the atmosphere is kept as little oxidizing as possible ; notwithstanding, a certain amount of slag is formed from the fusion of the oxide of iron coating the bars and its union with silica from the furnace bed when of sand, as is often the case; ferric oxide ores (" dry bottoms ") are preferable, yielding less cinder and causing less waste in consequence, whence the name. To avoid introduction of air, the doors for introducing and withdrawing the piles are banked up with small coal, &c. Gas forms a most suitable fuel, and various forms of gas-fired reheating furnaces have been introduced : thus in Sweden Eckman s gas reheating furnace has been in use many years, con sisting of a chamber in which charcoal is partially burnt by an air blast so as to form impure carbon oxide, which passes by a tube into the reheating furnace and is there burnt. Siemens regenerators applied to re heating furnaces have also been frequently employed, and with good results, either with his gas producers or with other forms of gas generator ; at Munkfors the Lundin gas producer (using damp sawdust, 10) is employed. Another form of reheating gas furnace is the Ponsard furnace (see 40). The chief advan tage of gaseous fuel for reheating furnaces is that the atmosphere can be much more exactly regulated so as to be non-oxidizing, thus avoiding waste by "cutting" (i.e., oxidizing) the piles ; independently of which, more over, a saving in cost of fuel consumed is effected ; thus Holley states that, in reheating Bessemer ingots or ordinary blooms in Siemens furnaces, 350 to 400 ft> of coal are used to the ton, whilst the ordinary fires would consume 800 to 1000 Ib. On the other hand, if the waste heat from the reheating furnace is used to generate steam, the saving in fuel that would otherwise have to be burnt for the purpose just about equals the difference in fuel consumption between the Siemens and the ordinary reheating furnaces. Price s retort reheating and puddling furnace (fig. 52) is a sort of combination of a gas producer and an ordinary puddling furnace ; the firegrate is supplied with fuel which has been heated in a low tower surmounting the grate by the waste gases circulating in a flue round the tower ; in this way the coal is coked, the gases passing to the iireplace ; a blast is introduced under the fire bars so as to burn the coke and produce a large body of flame of reducing character owing to the admixture of hydrocarbons from the coking process in the tower ; the blast is heated by passing through a chamber surrounded by the waste-gas flue ; by regulating it the atmosphere can be made more or less reducing at pleasure. The saving of fuel effected is said to amount to about one-third of that which would be required in an ordinary puddling furnace, whilst when arranged as a reheating furnace a still greater saving is produced. 1 Daring several years past a series of papers on " American Iron and Steel Works," by A. L. Holley and Lenox Smith, have appeared in Engineering, from which much detailed information may be gained as to modern American improvements in various directions. Utilization of Waste Heat. In all iron works the amount of heat escaping from the puddling and reheating furnaces (except when regenerative) is enormously in excess of the amount actually utilized ; to economize this waste heat to some extent, it is usual to employ the exit gases for raising steam, or for heating the air blast, or both. The actual amount of fuel employed in the operations of puddling and reheating (apart from that corresponding to the motive power) varies within wide limits according to the quality of the pig iron used in the first instance and the mode of operating adopted. When the coke refinery is employed a consumption of coke to the extent of 15 to 30 per cent, of the weight of the pig iron used usually suffices to produce a refined metal, which is then convertible into puddle bar with an expenditure of coal about equal to or somewhat exceeding that of the puddle bar made ; where particular manipulation requiring the working of only small batches at a time is practised, e.g., in some of the West Yorkshire iron-works, the consumption of fuel is often much larger, amounting in some cases to nearly double the weight of pig iron treated originally. In the ordinary pig boiling process, according to the purity of the metal, something between 100 and 150 parts of coal per 100 of puddle bar, and sometimes even more, are usually requisite, but con siderably smaller amounts are said to be used with some of the more recently invented kinds of furnaces. Analogous