DIFFERENT FORMS OF INJECTOR.
There are a great many different forms of injectors in use, but all of them conform to certain elementary principles in their mode of action. Steam passes from the boiler through the steam-pipe and receiving-tube A ([Fig. 1]) at a high velocity, and, combining with the water at the point B, condenses, but imparts considerable momentum to the water, which rushes along into the delivery pipe, raises the check-valve, and passes into the boiler.
Fig. 1.
The tubes of the injector are arranged so that a concentrated jet of steam shall impinge upon the water to force it through passages that are designed in the best form for maintaining the solidity of the current. The speed imparted to the water represents the work performed by the steam, and upon this velocity depends the successful action of the injector. As the current of water for starting the injector could not be induced against the constant pressure on the check-valve, which equals the pressure at the throttle, an overflow is provided where the water can flow unchecked till the necessary momentum is obtained, when the overflow is closed. All deviations in construction from the elementary injector shown in [Fig. 1] are made for the purpose of extending the action of the injector under varied conditions, for making it work automatically under different pressures of steam, and for improving its capacity to lift water above its natural level.