. The elements of railroad engineering . Fig. 307. g great depths to the earths surface; hence, g a very long piston rod is necessary. In the S lifting pump shown in Fig. 206 the water is raised from a point a few feet below the PNEUMATICS. 439 earths surface to a point considerably higher. This re-quires the piston rod to move through a stufifing-box, asshown at S, and also necessitates the rod being round, inorder that the water may not leak out. 1081. Force Pumps.—The force pump differs fromthe lifting pump in several important particulars, butchiefly in the fact that the piston is solid; t
. The elements of railroad engineering . Fig. 307. g great depths to the earths surface; hence, g a very long piston rod is necessary. In the S lifting pump shown in Fig. 206 the water is raised from a point a few feet below the PNEUMATICS. 439 earths surface to a point considerably higher. This re-quires the piston rod to move through a stufifing-box, asshown at S, and also necessitates the rod being round, inorder that the water may not leak out. 1081. Force Pumps.—The force pump differs fromthe lifting pump in several important particulars, butchiefly in the fact that the piston is solid; that is, it has novalves. A section of a suction and force pump is shown inFig. 208. The water is drawn up the suction pipe as before,when the piston rises; but when the piston reverses, thepressure on the water caused by the descent of the piston. Pig. the valve V and forces the water up the delivery pipeP. When the piston again begins its upward movement,the valve V is closed by the pressure of the water above it,and the valve Fis opened by the pressure of the atmosphereon the water below it, as in the previous cases. For anarrangement of this kind, it is not necessary to have a stuff-ing-box. The water may be forced to almost any desiredheight. The force pump differs again from the lifting pumpin respect to its piston rod, which should not be longer thanis absolutely necessary in order to prevent it from buckling^ 440 PNEUMATICS. Avhile in the lifting pump the length of the piston rod is amatter of indifference. 1082. Plunger Pumps.—When force pumps are usedto convey water to great heights, the pressure of the waterin the cylinder becomes so great that it becomes extremelydifficult to keep the water from leaking past the piston, andthe constant repairing of the piston packing becomes anuisance. To obviate this dif
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectrailroadengineering
