Application of ejectors. The Fig. [536], page 256, shows two ejectors applied in different ways. One is mounted to lift and force water, and the other to force only; the latter is submerged in the water to be elevated, and placed in a vertical position to reduce the condensation of operating steam to a minimum. In both of these examples of the use of the device it will be noted a strainer is attached to the suction pipe. The arrows show the direction of the flow of both the steam and water.
Certain ejectors will not work well when the steam pressure is too high. In order to work at all the steam must condense as it flows into the combining tube. Therefore, when the steam pressure is too high, and the heat is very great, it is difficult to effect complete condensation; so that for high pressure steam good results can only be obtained with cool water. It would be well when the feed water is too warm to permit the ejector to work right, to reduce the pressure, and consequently the temperature of the steam supply, as low pressure steam condenses quickly, and therefore can be employed with better results than high pressure steam.
Note.—This instrument is marketed as “Van Duzen’s steam jet pump” (Cincinnati, Ohio), and credit should be given the makers for the useful table on page 259.
For high elevations and high temperature of liquids, ejectors should be submerged from three to six feet; the suction pipe should always be provided with a strainer and the makers of the instruments recommend the placing of a check valve in the force pipe to facilitate the cleaning of the suction pipe by steam, when made necessary through the raising of impure substances.
To start the ejector open the steam valve slowly until the suction works satisfactorily, when full amount of steam should be quickly admitted.
Fig. 542.
Fig. 543.