Tuesday, February 5, 2013

RAM PUMPS for our region

Ram pumps have been around for many decades and are popular for two main reasons: 
They need no external source of power -- the force of moving water gives them the power they need. 
They are extremely simple, with just two moving parts. 

The basic idea behind a ram pump is simple. The pump uses the momentum of a relatively large amount of moving water to pump a relatively small amount of water uphill.

To use a ram pump, you must have a source of water situated above the pump. For example, you must have a pond on a hillside so that you can locate the pump below the pond. You run a pipe from the pond to the pump. The pump has a valve that allows water to flow through this pipe and build up speed. 
Once the water reaches its maximum speed, this valve slams shut. 
As it slams shut, the flowing water develops a great deal of pressure in the pump because of its inertia. 
The pressure forces open a second valve. 
High-pressure water flows through the second valve to the delivery pipe (which usually has an air chamber to allow the delivery pipe to capture as much high-pressure water as possible during the impulse). 
The pressure in the pump falls. The first valve re-opens to allow water to flow and build up momentum again. The second valve closes. 
The cycle repeats. 

The delivery pipe can rise some distance above both the pump and the source of the water. For example, if the pump is 10 feet below the pond, the delivery pipe might be up to 100 feet above the pump.

You can see that the one big disadvantage of a ram pump is that it wastes a lot of water. Typically, only about 10% of the water it consumes actually makes it up the delivery pipe. The rest flows out of the pump as the water builds momentum.

There is nothing magical happening in a ram pump. A different design that accomplishes the same thing might work like this: 
Water flows downhill from the pond and drives a water wheel. 
The water wheel is connected to a conventional shaft-drive pump (a reciprocating pump, a centrifugal pump, etc.) 
The pump moves water uphill. 

This design has more moving parts, but it accomplishes the same thing and has the advantage that it scales to any size very easily. The idea of using the energy of flowing water has been around for a long time!

Water, entering the steel drive pipe flows through it by gravitation until it reaches the RAM, passes through the RAM and out through the pulse valve into the waste drain. As the water flows, its velocity increases until the pulse valve is no longer able to pass the volume of water flowing: at this point the pulse value is suddenly closed. The outlet thus being closed, the flow of water suddenly stops. This produces a concussion of more or less severity in the body of RAM according to the height and distance from which the water is flowing. The result of this concussion is that a portion of the water in the body of the RAM is forced upwards through the delivery valve into the air cylinder. At the same time the recoil allows the pulse valve to return to its original position. The outlet being thus reopened, the water which was brought to rest by the closing of the pulse valve recommences to flow through the RAM until it acquires the necessary velocity to raise the pulse valve a second time, closing the outlet, producing a concussion and forcing more water into the air chamber through the delivery valve. The water, which is forced into the air chamber, finds its way through a pipe, known as the 'rising main', to the place where it is required for use with a continuous flow being maintained so long as the RAM remains working.

This series of events, which takes time to describe clearly, occurs from 40 to 90 times per minute, according to the size of the hydraulic RAM, the fall of the water driving the RAM, etc. The RAM will continue working automatically, the pulse valve rubber and delivery valve rubber being the only moving parts.

The fall of water necessary to work a RAM may be as low as 500mm (20 inches) and with such a fall, water may be raised to 18m (60 feet). With higher falls, such as from 2m (6.7 feet) to 7m (23.3 feet) and over, water can be raised to upwards of 300m (1000 feet) or more in height and distance is more or less unlimited: several of our ram installations pump to over 5km (3.13 miles).

Due to the action of the RAM, unless the conditions are unusually severe, and provided the RAM is kept working, it will be unaffected by changes in temperature especially low temperatures which might cause a conventional system to 'freeze up' unless some form of heat is provided.

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