HYDRAULIC RAM, an automatic ma chine generally employed to lift water from a low level to a higher one, but also to supply compressed air for motor purposes. The hy draulic ram operates by the momentum of a body of falling water. It consists essentially of a large pipe sloping downhill, the lower end rounding upward and being fitted with a heavy drop valve; and a small pipe reaching uphill to the point where the water is to be delivered. Back a few inches from the lower extremity of the pipe is attached an air-chamber connecting with the body
the pipe by an ordinary lift valve. The exit valve or '
It is evident that the pulse valve must be designed or regulated to suit the momentum of the water with which it is to operate: if it is too heavy it will not close at all, and the ram will not work; if too light, it will close before the stream in the drive pipe has attained its full force, and the result will be that so little water will enter the air-chamber that there will be practically no air pressure developed to lift the water in the lift pipe. The newer types of rams have a balanced lever with a sliding weight connected with the exit valve so that it may be adjusted with great delicacy to the available water power. The efficiency of the hydraulic ram depends upon the momentum of the flow of water in the drive pipe — that is, to its velocity multiplied by its mass. The ve locity being dependent on the vertical fall or head of water available, greater power at the ram is gained by increasing the mass of water moving in the drive pipe, by making it larger in diameter or longer. This will mean that
more water will flow into the air-chamber when the current is halted, and thus the air be com pressed to a greater degree, and consequently a higher or larger lift of water attained in the lift pipe. The formulas in common use by engineers for calculating the diameter and length of the drive pipe for any given condi tions are as follows: Diameter of drive pipe M where M is the volume of water continuously avail able in cubic feet.
Length of drive pipe=H-Fh÷ — X2 where H is the fall (perpendicularly) of the drive pipe, and h the height to which the water is to be carried in the lift pipe.
One of the difficulties to be guarded against in the operation of the hydraulic ram is the gradual absorption of the air in the air-cham ber by the water continually flowing through. Water under pressure dissolves a considerable quantity of air, and this has to be replaced, or the air cushion would become too small to be effective. An attachment to keep a sufficient supply of air always in the air-chamber is a low standpipe connected with the drive pipe at its base and to the air-chamber from its top, with suitable valves to take air from outside at low pressures, and force it into the air-chamber at high pressures.
The more common use of the hydraulic ram is to supply water from a lower level to a coun try house or dairy upon an elevation near by. It is also used by builders to get a water sup ply on the upper floors of new buildings where the water service fails. Ln the boring of the Mont Cenis tunnel the engineers used hydraulic rams to compress air to drive the rock drills employed, the compressed air being taken from the top of the air-chamber direct. The water power operating the rams was the natural drainage of the tunnel.
The pumping ram is designed raise a water supply separate from that which operates the machine, so that water that is not fit to drink may be used to deliver a supply of whole some water through the lift pipe. In this form of ram the momentum of the checked flow of water in the drive pipe expends its force upon a large area piston of a pump working in the lift pipe.
An industrial application of the principle of the hydraulic ram is made in the machine known as the 5hydraulic ram accumulator,' a device for storing water under great pressure, in some cases reaching 1,000 pounds per square inch. Consult Bradley, F. A., (Pumping and Water Power) (London 1912) ; Clarke, J. W, (Hydraulic Rams) (London 1907) ; Hutton, W., (Country Plumbing Practice' (New York 1914) ; Kennedy, R, (Modern Engines) (Lon don 1912).