The high pressure exhaust steam injector is shown in Figs. [537] and [538]—the last being an outline exhibiting the internal arrangement of the instrument: these injectors are made to work at all pressures up to and not exceeding 150 lbs. to the square inch.
Fig. 537 and 538.
The high pressure exhaust steam injector is worked by waste steam up to 75 lbs. pressure only, and a little live steam is introduced at the top of the injector to force water against pressures higher than 75 lbs. It will be noticed from sectional cut that the live steam does not come in contact with the water until after the exhaust steam has been condensed and has done its work. The exhaust steam alone gives an impetus to the water equal to 75 lbs.; it also heats it up to about 190° F. Its advantages are the same as those of the plain exhaust injector, the heat of the small jet of live steam which is used to overcome the excessive pressure being brought back into the boiler.
It raises the temperature of feed-water up to 90° Fahr. if working against a pressure of 105 lbs., and up to 86° Fahr. against 120 lbs. boiler pressure. It is regulated in the same manner as the plain exhaust steam injector.
It is not necessary to use live steam while working against any pressure below 75 lbs., when exhaust steam alone will suffice.
Fig. [539] represents the piping of the high pressure exhaust steam injector, the operation of which is described in the following paragraphs:
This injector can be worked under various conditions.