Ram Pump at the dipping pond
Curly Mills, a long standing supporter of The Ecology Centre, has designed and build a ram pump to move water from the loch into our new pond and to a water container which will serve our poly tunnel. Curly volunteered his time and skills to build this functional and educational feature for the site which is really quite amazing as it has to move water uphill - not an easy feat. Find out more below.
The Ram Pump Explained.
The Ram Pump is a very simple device which uses just two moving. It was patented in 1796 by Joseph Montgolfier who also invented the hot air balloon. The ram pump was commonly used before electricity was available to pump water and even today there are places where its simplicity and long life make it an ideal solution to the problem of pumping water to a high level. Although the pump itself is simple, it is not immediately obvious how it works, so a little explanation may be helpful:lthopughe
When you kick a ball, some of the kinetic energy of your leg is transferred to the ball as your foot makes contact. The ball (which is quite light compared to your leg) flies off at high speed and your leg is slowed down (but only a bit as it is quite heavy compared to the ball). So we are familiar with kinetic energy being transferred between different masses and that a slowing down a heavy object only a little can make a light object move fast.
In the ram pump, we compress some of the kinetic energy contained in a heavy mass of flowing water into a small amount of water which would squirt high into the air (if we wanted it to), in a similar way to the above example of kicking a ball either fast or high in the air. The ram pump consists of a long sloping tube with a door that can be suddenly shut so that the water flowing fast down the tube is suddenly stopped. This produces a pulse of very high pressure called `water hammer’; which you may have heard if you turn off a water tap fast (don’t try this at home as it can cause leaks).
But in the ram pump, we provide a branch route for the water to take when the main slope is suddenly blocked and so water can squirt past a `non-return valve’ in this branch. This is a little like what you see when a wave crashes into the rocks or a sea wall. You will often see a small amount of spray hurled high into the air by the impact and this is essentially what happens in the ram pump. When the ram pump door slams shut, we use the energy contained in the resulting pulse of pressure to force a small amount of water through against the back pressure of the non-return valve. The job of this valve is to make sure that water cannot run back which it wants to as the outlet pipe leads all the way up to the level of the poly-tunnel. The non-return valve is therefore under quite a back pressure and so only a comparatively small amount of water will have sufficient energy to squeeze through the non-return valve against this back pressure.
So to get enough water up to the poly-tunnel we need to arrange things so that the process of getting the water to speed down the sloping pipe, stop and then restart is automatic. We do this by having the outlet door hinged to open inwards and held open by a weighted lever attached to the door. The lever weight is adjusted so that when the water is stopped, the weight is heavy enough to open the door against the water pressure and even hold it open against the flow at first. But the door never opens completely and as the water flows past, it exerts a drag on the door which tends to close it. The more the door closes, the greater the closing force becomes and so once it starts to close, it quickly slams shut and produces the pressure pulse which squirts a little more water up through the non-return valve and into the pipe leading to the poly-tunnel. The weighted lever then re-opens the door and the cycle begins again. Provided that there is adequate water flowing over the dam, the Kinghorn ram pump will pump over one cubic metre of water i.e. 1,000 litre (over 200 gallons) in 24 hrs, more than enough to serve the needs of the pond and poly-tunnel and all without the cost complications of electrical pumps and switches.
The pond has a float valve so that water does not flood it and there is a tap at the poly-tunnel end. When both are shut, there is a pressure relief valve to vent the water and this prevents excessive pressure from causing damage. Commercial ram pumps are still made today and there is plenty of information on line e.g. http://www.greenandcarter.com/main/products.htm