In France, 1796, the Mongolfier brothers (known for their early work with hot air balloons) developed the first hydraulic ram pump, also known as a hydram. This automatic pumping system utilizes a small flow of falling water to lift a portion of the flow to a greater height than the falling distance. For example, a large flow of falling water passes through a small head to lift the smaller flow of water through a higher head. What makes the hydraulic ram pump a simple solution for water pumping and distribution is the fact that there’s only two valves, in regards to it’s mechanical construction. This gives the hydram a very high level of reliability, with minimal maintenance a considerably long operation life.

How does a Hydram work?

The impulse valve, also known as the waste valve since the water is not pumped on exit, will become open due to gravity or a small spring in some hydram designs. When the impulse valve is opened, water will begin to flow from the water source down the drive pipe and pass through a strainer. As the water flow accelerates, the hydraulic pressure beneath the impulse valve and the static pressure within the body of the hydram will become increasingly greater. This will eventually cause the necessary force to begin closing the impulse valve. When the aperture in the valve begins to decrease the pressure in the body increases, causing the impulse valve to slam shut. At this point, the moving water in the drive pipe is unable to exit through the impulse valve so it’s motion must decrease – this event will continue to promote an increase in pressure resulting in the delivery valve opening into the air chamber.

Depending on a phenomenon known as water hammer (a pressure surge or wave resulting when a fluid in motion is forced to stop or change direction suddenly) more than 50% of the driving flow energy is transferred to the delivery flow, making the overall efficiency quite impressive.

Once the moment occurs where the pressure exceeds past the delivery head, the water flow will begin to force its way up the delivery pipe. Simultaneously the air contained within the air chamber is compressed to a pressure which exceeds the amount of delivery pressure. The water within the drive pipe eventually comes to a stop and the static pressure in the body of the hydram drops near to the pressure of the supply head – causing the delivery valve to close once the air chamber pressure surpasses the hydram casing pressure.

Though the delivery valve is closed, water will continue to be delivered until the compressed air within the air chamber has expanded and the pressure becomes equal with that of the delivery head. There is also a component called a check valve which is required to prevent the return delivery of water. When the delivery valve is eventually closed, the decreased pressure in the hydram casing will enable the impulse valve to shut under it’s own accord – at which the cycle will start over again. Most standard hydraulic ram pump systems will operate between 30-100 cycles per minute.

In regards to components, the air chamber is by far one of the most vital. Apart from improving the overall efficiency by enabling delivery to proceed after the delivery valve has closed, it is also essential to lessen the shocks that would otherwise occur due to the incompressible nature of water.

The hydram cycle is timed and determined by the impulse valve characteristics. There is normally a pre-tensioned or weighted spring with an variable stop that will allow the maximum opening size to be altered at a moments notice. The amount of water delivered from a given drive flow is greatly influenced by the setting of this valve – and this is where one would dictate the hydram’s level of efficiency. If the valve remains open for too long or doesn’t remain open for a long enough period, the efficiency will be greatly reduced resulting in less water being delivered.

There is usually an adjustable bolt which is set at a pre-determined amount in order to limit the valve opening, encouraging peak performance of the hydram. Any seasoned hydram installer will be able to adjust the impulse valves settings for optimum performance output.