Rule for calculating the weight, which a Gas Metre of given dimensions, will raise to a given height, in a given time.
The following calculation will exemplify the power produced by a gas metre constructed to register 60,000 cubic feet of gas, in a day. The diameter of such a metre would be six feet, its depth three feet, and the depth of its rim eighteen inches.
The section of the rim would therefore contain 648 square inches, and supposing the pressure of the gas passing into the machine to be equal to a column of water two inches high, its buoyant power would then be equal to 1296 cubic inches of water, or forty pounds and a half weight. The mean diameter of the metre is 4 feet 6 inches, which multiplied by three, gives the perpendicular height that forty pounds and a half weight, would be raised by each revolution of the metre. The number of revolutions, in one hour which the metre makes, is 40, they would raise forty pounds and a half, 540 feet high in one hour.
Such a power is more therefore than sufficient to keep in motion the shaft of the lime machine.
Gas Holder Valve,—Siphon, or Water Reservoir.
This name is given to the principal hydraulic valve, by means of which a communication is established between the gas holder or gas holders, and the principal pipe, leading to the mains.
Fig. 7, [plate III.], exhibits a section of this valve. It is composed of an air tight box, A, A, A, A, containing a portion of tar, or water; d, is the inlet pipe which communicates with the gas holder, B the outlet pipe; which conveys the gas into the mains. C, C, is an inverted cup, furnished with a sliding rod, passing through a stuffing box, so that by means of the rod, the cup may be raised or depressed. For it is obvious that a communication will be established between the inlet pipe d, and the outlet B, when the cup is raised above the surface of the tar or water in the box A; and that the communication will be cut off when the cup is depressed into the tar. In the latter position the cup is shewn in the design. The sliding rod which raises and depresses the cup, passes through a frame E, E, affixed to the upper part of the box A, and which serves as a guard for the rod, so that it may be locked by means of a cutter passing through the sliding rod, and the frame of the box.
Fig. 3, [plate III.], exhibits a similar valve, which at the same time may be used as a water reservoir, commonly called a siphon, for collecting the water that may happen to accumulate in the mains, a provision which it is essential should be made at the lowest place, where two or more pipes incline towards each other. For it is obvious, that if a fluid should happen to accumulate in the angular part, where two descending pipes meet, to a height sufficient to fill the angular point, the communication between the two pipes would be completely cut off, so that the gas could not pass. x, x, x, x, fig. 3, is the reservoir; A, the inlet pipe; B, the outlet pipe; b, a short cylinder communicating with the exit pipe B, it is open at bottom and closed at top. D, d, the hydraulic cup which, when raised by means of the spindle e, closes the exit pipe B, by the open end of the cylinder b, becoming immersed in the tar or water contained in the cup D, d. The darts show the course of the gas when the valve is open: f is a small pipe furnished at top with a screw and covered with a cap; by attaching a hand pump to this pipe, the superfluous portion of fluid that may have accumulated in the reservoir, may be removed. c, c, is the equilibrium pipe, it connects the exit pipe B with the inlet pipe A, when the stop-cock with which it is furnished is opened. This pipe prevents the tar or water from being blown out of the hydraulic valves that may be interposed between the different descending mains of a district, as would otherwise happen, in consequence of the sudden concussion that takes place when the main or gas holder valves are opened. Because the gas in the mains, and the gas in the gas holders, are not in equilibrium. But by means of the small pipe c, c, the equilibrium is obtained when the stop-cock of the pipe c, c, is opened, and this should always be done before the main or gas holder valves are opened. For by neglecting this condition, the water or tar is liable to be blown out of all the hydraulic valves, that may happen to be interposed in the system of the pipes for conveying the gas, and communications are thus opened, which were intended to be shut.