The Steam Injector
A theoretical and practical treatise on the design and operation of injectors and on the flow of fluids through and the design of nozzles.

56 THE STEAM INJECTOR. The Control of said overflow pressure can be efi'ected. by providing a screw-down valve on the overflow chamber of any of the injectors illustrated in figs. 26 to 33, but this will be at the sacrifice of the automatic properties of the appliances, for should the jet passing through the com- bining nozzle break from any cause, the screw-down over- flow valve will prevent its escape; the steam will then force its way down the feed-water pipe. The object to be had in view with the hot-water injector must be, therefore, to provide automatic means for loading Fig. 33. or closing (during normal working of the applianoe) the overflow aperture or apertures at which the pressure is greater tlian atmospheric. The force for such automatic loading or closing of the overflow must be one dependent upon the working of the injector; that is to say, the force must only be operative when the injector is working normally. Such force is, to a certain extent, to be found in the pressure in the delivery chamber of the injector. The limita tion in the application of this force is that, even when the injector is not working normally, or no delivery is taking place therefrom but