Fig. 150.
Fig. 150 shows in section the construction of the ram in its simplest form in which E is the reservoir, A the pipe in which the water falls, B the channel, a and b the valves, C the air-chamber, and D the discharge. Water first flows out in quantity through the valve a, and as soon as it has acquired a certain velocity it raises that valve, closing the aperture. The impact thus produced, acting on the sides of the pipe and the valve b, raises this valve, and a quantity of water passes into the air-chamber shutting off air and compressing it in the space above the mouth d of the discharge D. This air by its electric force closes the valve b, and the water which has entered is raised in the discharge D.
As soon as the impulsive action is over, and the water in the channel A comes to rest, the valve a again falls by its own weight, the flow begins afresh, and when it has acquired sufficient velocity the valve b again closes, and the whole process is repeated.
The efficiency of hydraulic rams has been much discussed; exhaustive practical tests have been made and the results have been reduced to formulas. Whittaker’s Mechanical Engineer’s Pocket Book gives the following:
G × H
E = ——–
g × h
where E = the efficiency;
G = gallons of drive water used;
g = gallons of water raised;
H = height of fall, in feet;
h = height to which the water is raised, in feet.
The Table given on [page 174] is from the American Engineer. Its use is apparent, thus: when the height of fall in feet is, say 12 feet, and the elevation of discharge above the delivery valve of ram, in feet, is 30 feet, the efficiency or per cent., is ·3282. (Example) of 100 gallons 3282⁄100 gallons would be delivered.
Fig. 151.