HOT-FLUE, is the name given in England to an apartment heated by stoves or steam pipes, in which padded and printed calicoes are dried hard. [Fig. 563.] represents the simplest form of such a flue, heated by the vertical round iron stove C, from whose top a wide square pipe proceeds upwards in a slightly inclined direction, which receives the current of air heated by the body and capital of the stove. In this wide channel there are pullies, with cords or bands which, suspend by hooks, and conduct the web of calico, from the entrance at B, where the operative sits, to near the point A, and back again. This circuit may be repeated once or oftener till the goods are perfectly dried. At D the driving pulley connected with the main shaft is shown. Near the feet of the operative is the candroy or reel upon which the moist goods are rolled in an endless web; so that their circulation in the hot-air channel can be continued without interruption, as long as may be necessary.
[Fig. 564.] is a cross section of the apparatus of the regular hot-flue, as it is mounted in the most scientific calico works of England, those of James Thomson, Esq., of Primrose, near Clitheroe, Lancashire. a a a a, is an arched apartment, nearly 30 yards long, by 13 feet high, and 10 feet wide. Through about one half of this gallery there is a horizontal floor supported on arches, above which is the driest space, through which the goods are finally passed before they escape from the hot-flue, after they have been previously exposed to the hot but somewhat moist air of the lower compartment. A large square flue covered with cast-iron plates runs along the whole bottom of the gallery. It is divided into two long parallel vaults, whose sections are seen at u, u, [fig. 564.], covered with the cast-iron plates v v, grooved at their ends into one another. The thickness of these plates is increased progressively as they come nearer to the fireplace or furnace. There are dampers which regulate the draught, and of course the heat of the stove. h h are the air-passages or vent-holes, left in the side walls, and which by means of a long iron rod, mounted with iron plates, may be opened or closed together to any degree. k k are the cast-iron supports of the tinned brass rollers which guide the goods along, and which are fixed to the cross pieces represented by r r, [fig. 564.] l l are iron bars for supporting the ventilators or fans (see the [fan] under [Foundry]). These fans are here enclosed within a wire grating. They make about 300 turns per minute, and expel the moist air with perfect effect. s indicates the position of the windows, which extend throughout the length of the building. t is a gas-light jet, placed at the side of each window to supply illumination for night work.
The piece is stretched along the whole extent of the gallery, and runs through it in the course of one minute and a half; being exposed during its passage to the heat of 212° Fahr.
In [fig. 565.], A is the iron door of entrance to the hot-flue gallery; at b is the padding machine, where the goods are imbued with the general mordant. The speed of this machine may be varied by means of the two conical drums c c, which drive it; since when the band c c, is brought by its forks, and adjusting screws, nearer to the narrow end of the lower drum, the cylinder upon the same shaft with the latter is driven quicker; and vice versa. Over D D the cords are shown for drawing the drum mechanism into geer with the main shaft band F, F, E; or for throwing it out of geer. The pullies F F carry the bands which transmit the motion to the padding machine. A cylindrical drum exterior to the hot-flue, covered with flannel, serves to receive the end of the series of pieces, and to draw them through the apartment. This mode of drying the padded calicoes requires for each piece of 28 yards, 3 pounds of coals for the furnace when a fan is employed, and 4 pounds without it.