The use of the hydraulic ram is the solution of many an otherwise difficult problem in securing a supply of water in the country. It is only under certain conditions that the ram can be made use of, but when feasible it serves a valuable purpose without further cost than that of installing it.
In order to use the ram, the spring or other source of supply must be situated so that the ram may be located below it, with an opportunity for the waste water from the ram to be carried away from it. Such a location is usually to be found on a side hill.
The operation of the hydraulic ram is based on the following principle: When a body of water is discharged downward through a pipe running at an angle, and its passage out of the end of the pipe is suddenly stopped, the momentum which the body of water has gained, will force a part of the water to a much higher level than that of the water before it passed into the pipe. The connections of the hydraulic ram are to be seen in Fig. C of Plate 50.
In this case the source of supply for the ram is a spring located above it, as necessarily required. The water enters the ram from the spring, through a pipe which is called the drive pipe, its passage being checked by the waste valve when it attempts to escape. The momentum acquired by the water in falling through the drive pipe, forces whatever water is not lost through the waste valve, up into the air chamber, compressing the air in the latter. A check valve at the entrance to the air chamber prevents any escape of the water in a backward direction, and the compressed air of the air chamber forces it through the only other outlet, that is, through the force pipe, which carries it to the point of delivery. It is necessary to maintain a supply of air in the air chamber of the ram, and this is accomplished by an air valve, which admits air at each stroke, at a point below the air chamber.
The proper operation of the ram depends entirely on the working of the waste valve. When this valve is properly arranged, the action of the ram is continuous so long as it is supplied with water. In order that the valve shall be properly arranged to be self-acting, it should be weighted heavily enough to overbalance the pressure against its lower face. When a volume of water flows down the drive pipe from the spring, its weight and momentum is sufficient to suddenly close the waste valve. When this occurs the water in the drive pipe is for an instant without motion, and the force against the valve face is not great enough to keep it closed.
The valve therefore opens, the water in the drive pipe is again set moving, and in seeking to escape through the valve, again closes it. This alternate opening and closing of the waste valve thus continues without intermission, each descent of the water through the drive pipe forcing water up into the air chamber and thence to the point at which it is to be delivered. An overflow should be provided to the spring or whatever source of supply is used, in order that the water may always stand at the same height above the waste valve. If otherwise, the weight on the waste valve will not be properly adjusted, and the ram, therefore, not self-acting.
The air valve is an important feature of the ram. In all supply work, air is taken up mechanically by the water, and all air chambers in time lose their air by this means, and become waterlogged.
This would be a serious matter in the use of the hydraulic ram, as the operation of the weighted waste valve without an air chamber, would cause a violent shock at each stroke, which would be felt throughout the supply piping, resulting in a loud cracking and rumbling noise, and possibly in the destruction of the piping as well.
The air enters by virtue of the creation of a partial vacuum at the inner face of the valve, which allows atmospheric pressure to open the valve at each stroke and force in a small quantity of air, thus renewing any loss that the air chamber may have sustained.
Rams may be operated with a difference in level between the waste valve and surface of the source of supply of only 16 in., although a greater difference is desirable for good results. It is better practice to use a fall somewhat greater than actually required to perform the work, but not much greater, as an excessive fall means greater momentum, with a consequent greater wear and tear on the ram and piping. Five to 10 ft. is an amount of fall on the drive pipe that can generally be depended upon for good work. Manufacturers of the common makes of hydraulic rams claim that the ram will deliver approximately one-seventh of the water entering the ram, to a height approximately five times the difference of elevation of the waste valve and surface of the spring, and to a height twenty times such difference in elevation, one-fourteenth of the water entering the ram. The greater the height through which the water is to be raised, then, the greater will be the waste of water.
This waste of water is the one great obstacle, in many cases, to the use of the ram, as it generally requires a considerable supply to operate it. Rams or hydraulic engines are now made, for which the manufacturers claim a much higher rate of efficiency than can be obtained in the use of the common ram. While the action of the common ram depends upon the opening and closing of a heavily weighted valve, the valve in the modern hydraulic engine is made very much lighter, its opening resulting from the creation of a vacuum below the valve, and the weight on the waste valve being so regulated that the latter almost balances. This results in the rapid opening and closing of the valve, which in turn results in a quicker stroke. These and other improvements guarantee, as claimed by the manufacturers, 30 ft; of elevation of the water in the delivery pipe from the ram, for each foot that the water descends in entering the ram from the source of supply. This result, it is claimed, is accomplished with much less waste of water. The modern hydraulic engine will operate under any fall on the drive pipe, from 18 in. to 50 ft., will force water to a height of 500 ft., and is made in sizes capable of pumping any amount of water up to 1,000,000 gallons, during twenty-four hours.
The waste water should be carried away by a drain as fast as it collects in the ram pit, for if not, it will back up and prevent the operation of the ram.
The drive pipe of the ram should be about twice the diameter of the force pipe; it should run on an incline without other bends than the one necessary to carry it into the ram; and this pipe should be air-tight. The end of the drive pipe in the spring, should be submerged to keep out air, and be provided with a strainer to prevent entrance into the ram of foreign substances, as the lodgment of such substances on the valve may prevent its proper action.
In order to provide an unbroken incline of the drive pipe to the ram, when it is impossible to do so in the ordinary manner without making a very deep excavation, a tank or stand pipe with open end may be placed on the pipe at some point between the ram and the place where it is necessary to bend it, such tank or stand pipe being of sufficient height to allow water to stand in it at the same level as in the original source of supply.
A form of ram known as the double-acting ram is now built, and is of much value when the supply of pure water to be used for water supply is limited, and a poorer quality of water is also at hand. By means of this ram the poorer water supply is utilized to operate the ram, the latter delivering to the house-supply system only the pure water. The ram has a great variety of applications in country work, and is very generally in use not only for private supplies, but for supplying institutions, factories, etc., and even on public supplies of towns and villages.