. The elements of railroad engineering . ring the suction,the air thus compressed expands and acts as an acceleratingforce upon the moving column of water, a force whichdiminishes with the expansion of the air, and helps to keepthe velocity of the moving column more nearly air chamber is sometimes placed upon the suction air chambers not only tend to promote a uniform dis-charge, but they also equalize the stresses upon the pump,and prevent shocks due to the incompressibility of water. PNEUMATICS. 443 They serve the same purpose in pumps that a fly-wheel doesto the steam
. The elements of railroad engineering . ring the suction,the air thus compressed expands and acts as an acceleratingforce upon the moving column of water, a force whichdiminishes with the expansion of the air, and helps to keepthe velocity of the moving column more nearly air chamber is sometimes placed upon the suction air chambers not only tend to promote a uniform dis-charge, but they also equalize the stresses upon the pump,and prevent shocks due to the incompressibility of water. PNEUMATICS. 443 They serve the same purpose in pumps that a fly-wheel doesto the steam engine. Unless the pump moves very slowly,it is absolutely necessary to have an air chamber on thedelivery pipe. 1085. Steam Pumps.—Steam pumps are forcepumps operated by steam acting upon the piston of a steamengine, directly connected to the pump, and in many casescast with the pump. A section of a double-acting steampump showing the steam and water cylinders, with otherdetails, is illustrated in Fig. 311. Here 6^ is a steam piston,. Pig. 211. and R the piston rod, which is secured at its other end tothe plunger P. 7^ is a partition cast with the cylinder,which prevents the water in the left-hand half from com-municating with that in the right-hand half of the the piston to be moving in the direction of thearrow. The volume of the left-hand half of the pump cylin-der will be increased by an amount equal to the area of thecircumference of the plunger, multiplied by the length ofthe stroke, and the volume of the right-hand half of the cylin-der will be diminished by a like amount. In consequence 444 PNEUMATICS. of this, a volume of water in the right-hand half of thecylinder equal to the volume displaced by the plunger in itsforward movement will be forced through the valves V, Vinto the air chamber A, through the orifice D, and then dis-charged through the delivery pipe N. By reason of thepartial vacuum in the left-hand half of the pump cylinder,owing to thi
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectrailroadengineering
