. Supplement to Spons dictionary of engineering, civil, mechanical, military, and naval. dly preferable to use specialfirebricks, or lumps, for the lining, especially of largecupolas, although as a refractory material, ganister is scarcely to be surpassed, consisting of nearlypure silica, with a little oxide of iron and alumina. The firebrick lining except for portables, should have all the bricks laid as headers with fire-clay joints not exceeding about one quarter of an inch in thickness. FOUNDING. 623 The fireclay used for this purpose, and also for backing up the brickwork to the casing of
. Supplement to Spons dictionary of engineering, civil, mechanical, military, and naval. dly preferable to use specialfirebricks, or lumps, for the lining, especially of largecupolas, although as a refractory material, ganister is scarcely to be surpassed, consisting of nearlypure silica, with a little oxide of iron and alumina. The firebrick lining except for portables, should have all the bricks laid as headers with fire-clay joints not exceeding about one quarter of an inch in thickness. FOUNDING. 623 The fireclay used for this purpose, and also for backing up the brickwork to the casing of thecupola, should be the same clay as that from which the firebricks have themselves been made, sothat when at a high temperature, there shall be no tendency to any chemical reaction, such asmight be caused by only a slight variation in the constituents of the clay. Many furnace buildersmerely dip the bricks in a thick cream, composed of the same materials from which the brickswere made. The damp, loamy sand used for the bottoms of cupolas should not contain much alumina, and 1256*.. should be rammed well down, especially where it touches the walls. It should be about 6 in,thick, at the outer edge, slightly hollowed towards the centre, and with a good fall towards the taphole. When the cupola has a movable iron bottom, care must be taken not to put so little sand on itas to risk burning the trap away, wliilst on the other hand, if the bottom is too thick, it will bemore difficult to break down when it is wished to empty the cupola, especially if the sand containsa large percentage of clay, tending to make it bake hard and solid. The tuyeres for large cupolas may be protected from the heat to which they are exposed, in thesame manner as blast-furnace tuyeres, but the destructive action to which they are liable is lessthan that which blast-furnace tuyeres have to bear, where they carry in highly heated blast intothe furnace. Tiie usual method of protecting a tuyere is by keeping
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectenginee, bookyear1879
