Hydraulic Ram

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hydraulic ram

[hi′drȯ·lik ′ram]
(mechanical engineering)
A device for forcing running water to a higher level by using the kinetic energy of flow; the flow of water in the supply pipeline is periodically stopped so that a small portion of water is lifted by the velocity head of a larger portion. Also known as hydraulic pump.

Hydraulic Ram


a water-raising device in which the delivery of water is achieved by an increase in water pressure caused by periodically occurring hydraulic impacts. The hydraulic ram was known as early as the 18th century. The theory for it was developed by N. E. Zhukovskii in 1907. A perfected design of the hydraulic ram was offered by the Soviet engineer D. I. Trembovel’skii in 1927.

During the initial acceleration period (see Figure 1), a valve (4) is briefly opened manually. The pressure of the backed-up water then causes a flow through the feed pipe (6) at an

Figure 1. Schematic diagram of a hydraulic ram: (1) upper tank, (2) pipeline, (3) pressure chamber, (4) and (5) valve, (6) pipeline, (7) reservoir, (p) force required to open valve, (h) water height for fall, (H) water height for rise

average flow rate Q. This flow is discharged through the valve (4). When the force of water becomes equal to the weight of the valve (4), the valve is raised. Quick closure of the valve (4) and the consequent abrupt cessation of water flow causes a hydraulic impact (water hammer). A drastic increase in pressure opens another valve (5), which releases a quantity of water at an average flow rate q < Q. During the work cycle, water enters the upper tank (1) through a pipeline (2), having overcome the pressure H > h. Compressed air in the pressure chamber (3) equalizes the water flow through the pipeline. At the end of the second cycle the pressure in the valve box decreases slightly. Therefore one valve (5) closes and the other valve (4) opens, thus assuring the automatic repetition of the work cycle. The efficiency of hydraulic rams depends on pressure. For the ratio H/h = 1 the efficiency equals 0.92. For H/h = 20 it is 0.26.

Hydraulic rams are used in cases where the available water supply significantly exceeds consumption and where it is possible to install the equipment below the level of the water source. They are used in agriculture, in small-scale construction to provide a water supply, and so on.


Chistopol’skii, S. D. Gidravlicheskie tarany. Moscow-Leningrad, 1936.
Ovsepian, V. M. Gidravlicheskii taran i tarannye ustanovki, Moscow, 1968.
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