Fig. 210.—Diagram of a water-to-carbide acetylene-gas machine.
The “water to carbide” generator is shown diagrammatically in Fig. 210. As in the other figure, A is the generator and B is the gas-holder. A supply of carbide S is placed in the generator and water from a tank C is allowed to drip or spray onto the carbide. The gas collects in the gas-holder as before. This apparatus represents in principle the parts of a machine for generating acetylene by this process. The actual machines are arranged to perform the functions necessary to make the machines automatic in their action.
Whatever the type of the machine, the object is to keep in the holders a sufficient amount of gas with which to supply the demand made on the plant. Machines representing each of the types described are to be obtained, but the greater number of those manufactured are of the “carbide to water” form.
In the formative period of acetylene generators many accidents of serious consequence resulted from imperfect mechanism. Imperfections have been gradually eliminated until the machines which have survived are efficient in action and mechanically free from dangerous eccentricities.
The qualities demanded of a good generator are: There must be no possibility of an explosive mixture in any of the parts; it must insure a cool generation of gas; it must be well-constructed and simple to operate; it should create no pressure above a few ounces; it should be provided with an indicator to show how low the charge of carbide has become in order that it may be recharged in due season, and it must use up the carbide completely.
Because of the fact that the greater number of acetylene-gas machines of today are of the “carbide to water” type, in the description to follow that type of machine is used. They are generally made in two parts, one part containing the generating apparatus and the other acting as gasometer (gas-holder), but some machines are made in which one cell contains both the generator and gasometer.
In Fig. 211 is shown a two-part, gravity-fed machine, in which all of the internal working parts are exposed to view. The tank (a), as in the diagram, is the generator and the tank (b) contains the gasometer marked G. Each tank possesses a number of appliances which are necessary to make the machine automatic in its action. The part C of the generator contains the supply of carbide, broken into small pieces, a portion of which is dropped into the water whenever additional gas is required. The feed mechanism F is controlled by the gasometer bell G, which is buoyed up by the gas it contains. When the supply of gas becomes low, the descending bell carries with it the end of the lever F, which is attached to the feed valve; this motion raises the feed valve and allows some of the carbide to fall into the water. The gas that is immediately generated passes into the gasometer through the pipe P, and as the bell is raised by the accumulating gas the valve V is closed.
The gas as it enters the gasometer passes through a hollow device W, that looks like an inverted T, the lower edge of which is tooth-shaped and extends below the surface of the water. The gas, in passing this irregular surface, is broken up and comes through the water in little bubbles, in order that it may be washed clean of dust. This device also prevents the return of the gas to the generator tank during the process of charging.
