The Locomotive Of Today

The Boiler : Injectors, Exhazist Injectors. 53 and the pressure between the point of the combining cone and the steam cone becomes too great for the steam to over- come, the flap opens and at once relieves the pressure; then the steam, passing along, creates a partial vacuum in the cone, and draws down the flap, making it practically a solid nozzle. The overflow has a pipe affixed to the flange shown. Generally two injectors are Htted to each engine, in which case one would be litted with a plain pipe to the overflow, and the other with a screw-down valve, so that when it is desired to warm the feed, the overflow can be closed, and the steam blown through the injector as before mentioned. A third method is to have a series of passages or outlets in the combining cone, so arranged that when the injector is working properly the water passes by them, but when stopped suddenly the pressure relieves itself by escaping through the outlets to the overflow pipe. Holes are drilled in other cases for a similar purpose, and their action is precisely as last explained. D shows in horizontal section, a simple form of injector, very largely used; it has fixed nozzles, and is not of the re- starting type, so that if stopped by jerks it must be readjusted the same as the Giffard injector. In designing injectors the cones are generally settled as to shape by actual trial, and the size of the smallest part ot the delivery cone setties the size of the injector, its diameter being measured in millimetres. The reason the first two cones are made diminishing' is because the pressure of the steam has to be converted into velocity; then, when the water has been carried across the overflow gap into the delivery cone, this velocity is no longer required, therefore the next cone is made expanding, transforming the speed back again into pressure. A large number of injectors are made with flap valves covering the overflow orifice to prevent air being drawn up by the action of the stream of water passing the overflow gap and being foræd into the boiler. A release cock is fixed above the first non-return valve, for letting out all condensed water that collects in the delivery pipe, and some- times, instead of this cock, an elbow is provided with a union for attaching a pipe to the cab, to be there fitted with a cock and flexible pipe for watering the coals, etc. Exhaust injectors working by the aid of steam that other- wise would pass up the biast pipe, are largely adopted on some railways. For working these the biast pipe has a union fixed at or near its base, and a pipe is led away to the exhaust portion of the injector, where it meets the water and heats it up to a consiclerable temperature, and passes it along to the