In case the ram must be located at a considerable distance from the spring in order to attain the required fall, a standpipe D—slightly larger than the supply pipe—is used to take advantage of the full force of the water. In long pipes, the friction of the flowing water absorbs a considerable amount of the energy of flow and a standpipe, located as indicated at D, in the picture, will assure the full force of the flowing water in the ram.
The ram is commonly placed in an underground pit as protection from freezing during cold weather, and a drain from the bottom of the pit conducts the waste water away. The supply pipe or drive pipe B and delivery pipe C are buried underground below the frost line as a protection from freezing.
In Fig. 141 a sectional view of the ram shows all of the working parts. The air chamber G is shown partly filled with water; the impetus valve D is that part of the ram which checks the flow of the running water and forces a part of it through the valve E, at the bottom of the air chamber.
Fig. 141.—Cross-section of a single-acting hydraulic ram.
When inactive the valve D stands open and as the water enters from the pipe A, it flows through the valve to the waste pipe but as soon as the full force of the water bears on the valve it will suddenly close. This sudden stop of the flowing water will lift the valve E, and the energy of flow, due to its sudden stopping, will force some of the water into the chamber G. As this action occurs the upward pressure against the valve D is released and it reopens but immediately closes again as the water begins to flow. This process is kept up, each closure of the valve sending a little water into the air chamber. As the water gradually fills the air chamber, it is subjected to the same action as was described in the pressure tank, the air above the surface being compressed and the pressure developed in the space G forces the water out through the delivery pipe where it attains a force that is a factor of the height of the original fall.
The air in the chamber G, is subject to the same conditions of loss as that of the pressure tank, and to be assured of a supply to give pressure to the water, some air must be carried into the chamber with the water. For this purpose the valve F provided. After the chamber is partially filled, there occurs a reaction in the flow of water at each closure of the valve, which causes a little air to be drawn in through the valve F with each impulse. This air bubbles up through the water and enters the chamber where it assures an elastic cushion for closing the valve E.
The flow of water from the supply pipe is regulated at H by a nut on the stem of the impetus valve which permits its regulation. Closing the valve slightly causes a less supply of water to be delivered; opening the valve wider gives a greater supply.
Fig. 142.—Sectional view of a double-acting hydraulic ram.