The cheapest house constructed of sheet iron to surround a circular gas holder of 15,000 cubic feet capacity, supposing the surface of its cistern or tank to be level with the ground, costs no less than £. 320. The balance weights and chains £. 60, and the cast-iron framing for supporting the specific gravity machinery £. 150.
The cost of a gas holder of the before-mentioned capacity, will be £. 300, and a cast-iron tank for it, £. 800.—If the tank be constructed of brick-work, it will cost about £. 500, and if of wood (an iron-bound vat,) it will cost £. 600.
A governor or regulating guage adapted to a gas holder of from 10,000 to 40,000 cubic feet capacity, costs £. 50. In the construction of the gas holders, as hitherto described, it is always advisable when the situation will admit it, that the diameter to the height of the machine should be in the proportion as three to two. If these dimensions be observed, and the gas holder is not burdened by iron stays, it will not displace a column of water more than one inch and a half in height. And by adapting to the machine, a governor or regulating guage, a considerable saving will be effected. The gas holder may then be constructed as shown fig. 7, [plate VI.], or fig. 2, [plate V.] A circular gas holder of 30,000 cubic feet capacity, if properly constructed, weighs no more than eight or nine tons, including its wooden curb at its lowest extremity, and its diagonal stays.[40]
[40] Mr. Lee of Manchester supplies his house, two miles distance from the manufactory, by means of a portable gas holder.[41] A small carriage upon springs conveys two square close gas holders made of wrought iron plates, and each containing fifty cubic feet of perfectly purified gas, equivalent together to about six pounds of tallow. Each gas holder weighs about 160 pounds; and has a valve at the bottom, which is opened by the upright main pipe, the moment the gas holder is immersed in the pit. The strength of one man is found sufficient for the labour of removing the gas holder from the carriage to its place.
[41] Henry’s Experiments on the Gas from Coal, in the Memoirs of the Manchester Literary and Philosophical Society, 1819.
The roof of the machine ought to be constructed of thicker sheet iron than those forming its sides. The only object of the balance weight, is to counterpoise the weight of the chain of the gas holder of the old construction, so that when the gas holder is wholly immersed in the cistern, the chain and balance weight are in equilibrium, deducting the required pressure with which the gas holder is intended to act. And this ought never to exceed from half an inch to an inch perpendicular head of water.
The sheet iron best adapted for constructing gas holders, is that known in commerce as No. 16, wire guage.[42] Gas holders made of plates of iron of this kind, have now been in use for upwards of nine years, and are not in the least injured or decayed. Self-interested views may sometimes lead unprincipled workmen to make use of sheet iron plates of a much greater thickness, but experience has sufficiently shown that any greater thickness than what has been specified is wholly unnecessary, and only serves as a drawback to the facility of the general operation.
[42] A superficial foot weighs three pounds.
Revolving Gas Holder at the Westminster Gas Works.
The revolving gas holder is an ingenious contrivance invented by Mr. Clegg, for storing large quantities of gas. A gas holder of this construction may be erected with advantage in situations where the nature of the ground will not admit of a deep cistern either above or below the ground being constructed, without an enormous expence.