Hydraulic Rams are sometimes employed, their action being as follows: A supply pipe S, in picture 52, is taken from the reservoir to the Air Vessel or ram A. A finely balanced valve is fixed at V whose weight is a little greater than the water pressure from the reservoir, and hence when the water is at rest in the supply pipe the valve V opens downwards and water runs to waste. As the velocity of the water increases the valve V is closed and the momentum opens the valve W, and water is thus forced into the air vessel, in which the air is compressed, and by its reaction the water is forced up the delivery pipe D. The pressure in the supply pipe is thus diminished, and both valves therefore fall and the water escapes at V until this valve is again closed by the impact of the water due to the increased velocity, when more water enters the ram and is raised higher in the delivery pipe. This action is continually repeated while the supply in the reservoir is maintained. It is estimated that about one-eighth of the water is wasted.
Picture 52. Hydraulic Ram.
The length of the supply pipe should not be less than three-quarters of the height to which the water is to be raised.
The diameter of the supply pipe should be equal to 1.45 Q and the diameter of the rising pipe should equal .75 Q.
The contents of the air vessel should be the same as that of the rising tube. One-seventh of the water may be raised to four times the head of the reservoir, or one-fourteenth eight times, or one-twenty-eighth sixteen times, etc.