[PLATE VI.]
[Fig. 1.] Exhibits a design of the gasometer framing, or skeleton, which serves to give stability and strength to the gasometer. It consists of wooden frame work, marked A, A, A, interlaced with iron rods, B, B, B, &c. The whole framing is so disposed that it will float in the cistern horizontally, and therefore keep the gasometer perfectly steady and level with the surface of the water.
The rest of the sketches represent various kinds of gas pipes employed as mains for conveying the gas, and the methods of connecting them.
[Fig. 2.] Represents a longitudinal section of a Spigot and Faucet Pipe. These kinds of pipes are applicable in most cases as mains for conveying gas. A, is called the spigot, and B, the faucet. They are joined together, and made air tight, by iron cement, the composition of which is as follows:
Take two ounces of sal ammoniac, one ounce of flowers of sulphur, and sixteen ounces of cast iron filings or borings. Mix all well together, by rubbing them in a mortar, and keep the powder dry.
When the cement is wanted for use, take one part of the above powder, and twenty parts of clean iron borings or filings, and blend them intimately by grinding them in a mortar. Wet the compound with water, and when brought to a convenient consistence, apply it to the joints with a wooden or blunt iron spatula.
By a play of affinities, which those who are at all acquainted with chemistry will be at no loss to comprehend, a degree of action and re-action takes place among the ingredients, and between them and the iron surfaces, which at last causes the whole to unite as one mass. In fact, after a time, the mixture and the surfaces of the flanches become a species of pyrites (holding a very large proportion of iron,) all the parts of which cohere strongly together.
The inner parts of the faucet ought to be no larger in diameter than just to fit the spigot. This supports the pipe, independently of the cement, and prevents the risk of hurting the joint from any external stress. The inner faucet is commonly made about 21⁄2 inches deep, and has the spigot inserted 11⁄2 inch into it. The practice of some workmen, is to make the outer faucet, or that which contains the cement, six inches deep, for all pipes above six inches diameter; and to make the faucets of all pipes below six inches, the same depth as the diameter of the pipes. It is usual to make the space for the cement, all round the spigot, from 1 to 11⁄2 inch; that width is required, in order that the cement may be firmly driven into the joint. When the space is very narrow, this cannot be done. On the other hand, when too wide, there is a waste of cement, and a risk of injury from unequal expansion.
[Fig. 3.] Exhibits a profile view of these kinds of pipes when joined together. The spigot and faucet pipes are liable to burst from the great expansion of the spigot, and the risk of this accident is increased by increasing the space between the spigot and faucet, which requires to be filled with cement.
[Fig. 4.] Represents a longitudinal section of two flanch pipes, and the modes of connecting them. A and B, show the parts of the pipes; and C and D, the flanches. These pipes are also joined together, and rendered air-tight, by interposing between the flanches rope-yarn, hemp, or some other pliable material, and iron cement, and then screwing up the faces of them by means of the bolts and screw nuts.