Page:Encyclopædia Britannica, Ninth Edition, v. 13.djvu/340

 324 IRON in the Siemens puddling furnace (fig. 33). The far end is cooled by water or steam ; the fuel employed is gaseous, the generator being immediately in front of the furnace ; mechanical arrange ments of special character are also applied for the purpose of charging and discharging the furnaces. The rotating chamber rests on friction wheels which are made to turn by an engine instead of having an external cog wheel affixed to the drum itself as in Danks s machine. For drawings of the machine and further details see Iron, vol. x. p. 738. Spencer s rotating furnace (fig. 38) is shaped like a rhombus reversing on a horizontal axis, supported at the end by disks per pendicular to the axis of rotation ; the transverse vertical section is square, two sides being parallel to the axis, the other two, though parallel to each other, being pitched slightly diagonal, so that in revolving a throw is communicated to the charge from bridge to Hue during one half of the revolution, and vice versa during the other half. The flat sides allow the rotator to be readily fettled ; they are made of troughs filled with molten tap cinder, the ends being made up of bricks also of cast tap cinder, the whole put together and cemented with molten tap ; in one side is the door for removing the ball when it has come to nature. The pig is melted in a cupola before running in ; in about five minutes the boil commences, and it lasts about ten minutes, the operation being finished in other ten, when the ball is extracted, and quickly re moved on a bogie to the hammer and rolls. Crampton s furnace has a similar construction, with the addi tional modification that the flame is produced by coal dust and air ( 10) instead of solid fuel (fig. 39). A is the revolving chamber supported on friction rollers C, C ; B is the refractory lining, and D a movable flue piece, supported upon a pivot D so as to wheel round when required into the position indicated by the dotted lines ; it is kept in place against the furnace by the screws d, d when the operation is proceeding. By means of the injecting pipe G a jet of mixed air and small coal is blown into the furnace ; this pipe is adjustable so that the flame can be directed into the furnace in diil erent ways as required ; when a number of furnaces are worked together from one central air and coal reservoir, each one is fed by a pipe G radiating from the reservoir. By means of little doors /, / different parts of the opening F in the flue piece through which the jet enters can be closed at will. A water jacket surrounds the rotator fed through the two-way cock H with a stream of water cir culating as indicated by the arrows entering by the pipe I, and passing through the jacket JJKLL to the exit pipe N, after which it passes to the flue piece D (by means of a flexible; tube), and there circulates through another analogous jacket, finally emerging by a pipe and running into a chamber d at the base of the pivot and FIG. 38. Spencer s Revolving Puddling Furnace. I. Plan on line A B. thence to the drain. The wearing joints 0, of the furnace and Hue which rub together are iron rings, directly in contact with the water (forming the ends of the jackets); these are renewable when required. In fettling the furnace either oxide of iron bricks moulded to fit the furnace are built in and then baked in situ, and fettled in much the same way as Danks s furnace (viz., melting fusible ores or cinder, and throwing in irregular lumps of ore, splashing the cinder over the far end in so doing so as to cover it) ; or hammer slag, &c. , is melted on the bare iron casing, and lumps of ore are thrown into the fused substance so as to be thereby cemented to the casing ; or a thin firebrick lining maybe built in and the fettling then put on. Owing to the cooling action of the water-jacket when the furnace is in use, the bricks are never melted down, and even a fluid cinder applied directly to the iron plates in the first instance without bricks of any kind is completely prevented from fluxing ; in the same way the far end gets spontaneously fettled by the consolidation of the cinder splashed against it. According to Crampton s description of the furnace (from which the above account is abridged Journal I. andS. List., 1874, 334), in puddling 130 cwts. of pig 147J cwts. of hammered iron were ultimately produced, with an expenditure of 70 cwts. of coal, i.e., the wrought iron was 113 5 per cent, of the pig used, and the coal employed was 47 3 per cent, of the wrought iron made (or 9 46 cwts. per ton); in another case, with smaller charges, the coal consumption was 701 per cent, of the wrought iron (14 02 cwts. per ton), which amounted to 114 5 of the pig used. Pig containing nearly one per cent, of phosphorus yielded wrought iron containing only traces. Hoicson and Thomas s Rotary Machine. The chamber is made up of two cones of wrought iron fixed base to base, lined with bricks made of ferric oxide and previously well-baked, ilmenite or haema tite or any refractory ore being suitable. The fireplace communi cates with an annular space surrounding the neck of the chamber nearest to it by a tube, so that any air which would otherwise be drawn in by the draught at the opening between the grate bridge and revolver is drawn over to the fire and not into the chamber. In order to withdraw the ball, and introduce a new charge, the revolver is mounted on a carriage (supporting the friction rollers), so that by running the carriage backwards or forwards, in a direction perpendicular to the axis, access is had to the interior through the ends, or the chamber is again put into position. Fdlcy and Henley s Furnace. This furnace has a bowl-shaped bed vhich revolves on a vertical axis by machinery, the sides and roof being fixed ; when the pig is introduced and melted down, the workman inserts his rabble at the working door, and has simply to hold it in position to stir up the molten mass, this being facilitated by a projecting stud beinyj fixed to the rabble and fitting into a cavity in the doorplate. When the metal begins to come to nature, it is worked with a differently shaped tool something like a plough share in shape ; this, being pressed against the bottom, causes the plastic mass to roll over the plough like a small cascade ; finally the