Possibilities for Locally Fabricated Hydraulic Ram Pumps
Possibilities for Locally Fabricated Hydraulic Ram Pumps by: Steve Gibson Extension Agent, Agriculture and Farmer to Farmer Coordinator, North Carolina Farmer to Farmer in NC is a program through Partners of the Americas North Carolina is partnered with the Cochabamba region of Bolivia. Mauricio Ramirez Parra is the Cochabamba coordinator
Hydraulic ram pumps use the inertia created by a flow of water in a pipe that suddenly stops to pump a portion of this same water uphill. It is necesary to have at least a 3 foot drop in a creek. This can be from a natural drop or one created by a dam. This drop is called the drive head. The height that the water is pumped from the ram itself to the point of use is called the delivery head. This typically must be 2 to 3 times the drive head for the pump to work since back pressure is required. The higher the water is pumped, the less is delivered. The use of tanks in low flow situations allows for significant amounts of water to be collected since ram pumps work all the time. Before rural electrification rams were used extensively in many areas of the United States. Currently they are used in some developing countries and in rural areas where electricity is not economically practical or available. Rams can be used to water livestock, supply water for homes and communities and even for small scale irrigation. The amount of water delivered and the height of delivery depends on the water source and the terrain. For practical planning purposes the delivery head is typically no more than 10 times the drive head although water can be pumped higher in some situations.
High performance rams such as this one are very expensive. These pumps are able to use high drive heads and deliver water to very high delivery heads. Medium performance rams are available also and typically are made of PVC. A skilled and dedicated person can make ram pumps, even high performance ones with readily available materials. Several plans are available via the internet.
Pumps can be of different sizes such as the one on the left which I call “the monster ram.” It uses a 4 inch drive pipe and delivered 17 gallons of water a minute. A much smaller pump such as the one on the right will deliver much less. With a 5 ft. drive head it delivers about 3 quarts per minute to a 28 foot delivery head. It could almost be put together on the plumbing supply company counter using standard plumbing components.
The monster ram in action and its output uphill of 17 gallons per minute. I estimated that it uses over 65 gallons per minute.
The basic parts of a ram pump system are: <ul><li>A water source and supply pipe </li></ul><ul><li>Body of water which may be the source itself to supply the drive pipe. A drive tank or standpipe can be used also </li></ul><ul><li>The drive pipe, typically of galvanized steel but for low performance pumps, PVC can be used </li></ul><ul><li>The pump itself </li></ul><ul><li>A delivery pipe or hose to the point of use </li></ul>
This diagram shows the source of water being used as the body of water to supply the drive pipe. Systems like this are possible in regions with many natural drops in the creeks. High drive heads are easily obtained and typically high delivery heads are required in these regions.
This diagram shows a system using a drive tank which is supplied by a supply pipe. To reduce friction loss of water flow, the supply pipe is typically larger than the drive pipe. Drive tanks can be used to operate more than one ram pump if the supply pipe is large enough. The supply pipe can be very inexpensive drain material. In this example the water is used for a community water system. ------------------- ---------------- Delivery head
This diagram shows a ram pump system using a standpipe. This is easier to install than a drive tank. Since the body of water in the standpipe is not flowing it can freeze up and cause system failure in very cold temperatures. In contrast a system using a drive tank gives much less trouble since the volume of water is much greater and its temperature stays higher during the colder night hours. A tank may also be used in the supply line to allow sediment and sand particles to settle out prior to the water reaching the pump. ------------------ -------------------------------------------------------------------- Drive head
A spring which has been dammed in order to collect water for ram pump systems. The supply line will go to a drive tank shown in the next photo.
A drive tank. The supply pipe is to the left. Coming from the tank is a galvanized pipe which supplies a small ram pump. Also coming from the tank is a PVC pipe which will go to a standpipe that supplies another small ram pump (in this case technically the tank is a settling tank). The next photo will show the standpipe.
A standpipe which operates a ram pump (drive pipe has been buried in the sand). Note the valve to cut off the supply of water. Also note the screen material on the top to keep out falling leaves, etc.
A dam in a creek. These can be difficult to maintain during heavy rains. This water supply directly supplies one small ram pump and also supplies a drive tank for another ram pump. In many areas dams are necessary to create the drive head.
The Basic Parts of the Pump Are: <ul><li>The impulse valve </li></ul><ul><li>The delivery valve </li></ul><ul><li>The air vessel </li></ul><ul><li>A snifter valve or hole </li></ul>
There are several possibilities on how these parts are arranged. Also an air package similar to the bellows in a well pump tank can be used instead of the snifter valve or hole. The purpose of the snifter is to replenish the air in the air vessel. As the system operates some of this air dissolves in the water flow. The air in the air vessel serves to cushion the water hammer effect when the delivery valve closes. This pump has the impulse valve downstream. The delivery valve is inside the pump (see large arrow). This pump has a sight tube to monitor the air in the air vessel. Also note the snifter valve (small arrow). Snifter valves or holes are located upstream from the delivery valve.
This pump is the same size as the previous one but the impulse valve is on the upstream side. It is designed so that the delivery valve and the moving part of the impulse valve can easily be removed on site for cleaning or replacement. Water from drive pipe to enter here Delivery valve No snifter has been installed. For this pump a snifter hole will be used and drilled after installation. If the pump operates without severe vibration, the snifter hole functions properly, replenishing the air in the air vessel. Site tubes are optional.
Understanding How Rams Work To successfully fabricate ram pumps it is essential to understand how they work. The following diagrams help to give a simple and brief explanation. Hydraulic ram pumps work best and are more trouble free if the system has some sort of water filtration. The filters can be easily made from standard hardware items. The filter on the left is for use at the intake of the water source. The one on the right is used in the drive tank itself.
Lets start with the impulse valve open and water flowing out of it. We are starting at the beginning of what is commonly called the acceleration phase and the delivery valve is completely open. Note that the back- pressure in the delivery pipe is keeping the delivery valve closed With the movable part of the impulse valve completely dropped the speed of the water in the drive pipe is increasing. This example depicts a ram using a brass swing check valve. High performance locally fabricated ram pumps should be made of metal components. Some plans for locally fabricated pumps suggest using modified well foot valves for the impulse valve.
The velocity of the water has increased and the movable portion of the impulse valve is starting to close. The exact time that this occurs depends on many factors such as drive pipe length, drive head and the adjustment of the impulse valve maximum opening. It is important when designing a ram pump to have a way to adjust the maximum opening. With a smaller opening less water is used and of course less is delivered. However if the water flow in the creek decreases in dry periods the ram pump can be adjusted to allow continued operation. This diagram shows the end of the acceleration phase. In reality the flow of water up the delivery pipe is continuous because of the cushioning effect of the air in the air vessel. If the air volume is not sufficient the pump will vibrate and the delivery of water will be in surges.
This diagram shows the delivery phase. The force of the accelerating water has overcome the weight of the movable part of the impulse valve and the flow of the water has suddenly stopped. This sudden increase in pressure overcomes that of the water in the delivery pipe and of the air in the air vessel. As a result the delivery valve is forced open and a portion of the water is forced up the delivery pipe. The diagram shows a flapper type delivery valve which can easily be made using a round disc with holes drilled in it and flat flexible material such as inner tube rubber or vinyl. Standard plumbing check valves can be used but the flapper type if made properly is more efficient and can be very inexpensive.
After the water suddenly stops there is a rebound effect. People notice this same thing when water is suddenly cut of in a home. It is usually called water hammer. It can be compared to a kicked soccer ball bouncing off of a brick wall. A vacuum is created and this allows the moving part of the impulse valve to drop or open. This phase is commonly called the recoil phase and when the valve completely opens the acceleration phase begins. So we have observed a full cycle. Another thing happens during the recoil phase. The vacuum created causes a small amount of air to be sucked through the snifter valve or snifter hole. In this diagram a snifter hole is shown just under the closed delivery valve. The air must be sufficient to replace the air in the air vessel that dissolves into the water as the pump operates.
The Drive Pipe, Very Important! The drive pipe is very important, ideally it is composed of non flexible material such as galvanized pipe. However for low performance systems schedule 40 or 80 pressure PVC can be used. The ram pump shown here is a high performance pump with a 15 foot drive head and it uses a galvanized drive pipe. Note that in this pump there appears to be no air vessel. The portion to the right contains an air package, a pneumatic insert. The material however did not hold the pressure for long and eventually developed a hole and failed completely. Many plans suggest bicycle or wheelbarrow inner tubes but a well functioning snifter valve to keep the air vessel with adequate air is preferred.
Galvanized pipe is very expensive. Thinner walled galvanized fencing material can be put together and secured adequately as shown below. Performance should be almost equal to pipe. The cycle time is faster with metal drive pipes. During the delivery phase a shock wave travels up the drive pipe and must dissipate prior to the beginning of the acceleration phase. This shock wave travels at the speed of sound in water. The speed of sound in water is faster in a galvanized pipe compared to a plastic PVC pipe. The shock is “reflected back” from the water in the source, drive tank or stand pipe to the ram pump. This wave may be “reflected” from the pump itself and up the drive pipe again if it has not completely dissipated. Drive pipe length also determines cycle time. It is generally considered ideal to have drive pipe lengths 500 to 1000 times the drive pipe inside diameter and/or 5 to 6 times the drive head.
Maintenance of a Ram Pump <ul><li>The following sequence can give an idea of how locally fabricated pumps can be made and some of the problems that require some regular maintenance. In addition grime buildup in the drive pipe can decrease efficiency and it is a good idea to clean and flush the drive pipe as needed. </li></ul>
This is a low performance plastic PVC ram pump, a modified 3 inch version of a 4 inch pump designed at Warwick University in England. It is disassembled but the parts are in relative positions. Note that it is on a wooden base. Rebar pieces were used to secure it on the creek bed. When working properly with a 5 foot 6 inch drive head this pump delivered water at the rate of 2.5 gallons per minute to a site 29 feet above the pump itself. Low performance pumps like this one should not be used with drive heads over 10 feet. This pump was designed to provide sufficient water for small scale irrigation of crops and also to be economically made in developing countries. The plans for the 4 inch version are on line and give instructions on how to save money by making some of the pipe fittings.
These are views of the impulse valve. It is made from 3 inch Schedule 40 PVC and several layers of smaller pipe (pressure and drain PVC) cemented together. The 3 inch piece has 51 mm holes drilled for the water to exit. The movable portion is of the layers and it pivots on a hinge which allows it to drop at both of its ends. Note the bands of thin PVC drain pipe which can be placed on the valve body at the arrow to reduce the distance that the movable portion falls. This will be useful when stream flow decreases since the pump will not use as much water.
Over time and especially after periods of very heavy rain sediment can accumulate in the ram pump. During floods if the water in the creek is over the impulse valve, the pump may actually stop. In this picture it can be seen that maintenance will be required after heavy rains. Even if adverse weather does not occur grime buildup will reduce efficiency. Note the grime from the delivery valve disc on the screwdriver and the sand and silt deposit from the impulse valve pipe.
Views of the delivery valve after cleaning. This valve uses an aluminum disc which is about 1/4 th inch thick. The drilled holes are 5mm. The flexible material is commercial but I have used several layers of inner tube material and currently am using some vinyl swimming pool liner material. The holes in the disc are slightly enlarged on the side opposite the flexible material so water flow will be less inhibited. For smaller ram pumps a heavy plastic disc can be used. The pressure of the water in the delivery pipe will in time warp the disc material unless it is made of the proper material.
Gasket sealing material is useful to obtain watertight seals. For this ram pump the removable portions are held together with threaded rods. Wing nuts are useful for quick work on the pump, even without taking it out of the creek.
This ram pump is driven by a 1 inch galvanized pipe. Drive head is 15 feet. I measured one gallon and a pint delivery of water per minute at a point 48 feet above the ram. Previously I had a pressure gauge and cutoff valve on the delivery pipe of this pump. With the valve closed, 80 psi was generated. This indicates that the pump could deliver some water up to 185 feet. One pound per square inch of water is equivalent to 2.31 feet of head. I consider this ram high performance. All components are metal or double thickness schedule 40 PVC. Note that the impulse valve is a 1 ¼ inch swing check valve. The movable part of the valve pivots on a shaft at the arrow.
To adjust or “tune” this pump all you need to do is change the angle of the impulse valve. In the upright position the moving part of the valve is able to drop completely which allows maximum water flow. When water flow in the creek is low or if not as much delivery water is desired, the angle of the impulse valve can be moved in the direction of the arrow. This position prevents the valve from allowing maximum flow. As a result not as much water is used nor delivered. A standard check nut can be used at the small arrow to hold the valve angle in place. When a ram is “tuned down” the number of cycles per minute or beat rate is increased.
This is the ram shown in the previous photo taken apart for cleaning of the delivery valve. This valve because it is smaller in diameter than the first one we took apart is able to use a plastic disc. On this ram I used 3 layers of inner tube material for the flapper. The swing check valve typically stays free of debris and grime. However sometimes the pivot can wear out. One that I made from a 1 inch swing check valve wore out after 6 months of use. The one on this ram has lasted much longer.
The Snifter Valve or Hole This photo and diagram shows a snifter valve. It is made of a rubber washer held in the pump just upstream of the delivery valve. I usually use the smallest drill bit I have and if air replenishment is not sufficient increase the size or number of the holes.
Instead of a valve a very small hole can be used. These photos show the drilling of the snifter hole in the pipe just below the delivery valve disc. When operating very little water or pressure is lost when the impulse valve closes. I also like to place a small section of PVC drain material over the hole. This method is very simple but very little efficiency is lost. Previously I had a air package for this pump but it failed.
Tips on Making a 3 Inch Ram The following series of photos will demonstrate some important steps and procedures to use when locally fabricating hydraulic ram pumps
Perhaps the most time consuming part of fabricating a pump like this one is making the delivery valve. First the valve disc must be cut out. It is essential to have a drill press. The hole saw shown works ok and is good since any size disc can be made. The disc will need to fit snugly inside a PVC fitting. Also standard hole saws can be used but sometimes the disc is not exactly the correct size. Next a paper template is taped to the disc. I used the template for the Warwick University 4 inch ram pump but with a compass made it smaller to work on the 3 inch ram.
Next very carefully use a punch, then a pilot bit to make the pilot holes. I use a screw to attach the disc to a piece of heavy board to drill the holes. It is very important to set the chuck speed at the recommended speed for the material and drill bit size. By using the heavy board it is not necessary to clamp the disc each time a hole is drilled. The bit size is 13/64 inch.
After all of the machine work the disc must be cleaned up with a file. Also the holes on the side of the disc away from the flexible material are slightly enlarged with a larger drill bit. This will allow the water to flow through the holes with less friction loss. It is very difficult to get all of the holes exactly placed so it is essential to use the paper template. A person with much patience a good eyesight is best able to use the punch to mark the holes.
Next the flapper material is marked with a compass or by using a fitting as a guide and carefully cut out. I am trying a new material here, vinyl swimming pool liner. A small piece of PVC pipe is very carefully drilled and screws with self locking nuts are used to attach the flappers to the disc. When the water during the delivery phase pushes the flappers away from the disc they must completely clear the PVC. For this valve I chose to use 3 layers. The material must withstand the pressure within the delivery pipe without being pushed back through the holes in the delivery valve disc.
For making square cuts for the pipe part of the delivery valve a miter saw is very useful. To mark a straight line use a carpenters level on a flat floor. Next very carefully use a hole saw to cut out the impulse valve holes. This design has 5 holes. PVC can be difficult to drill without gouging. Therefore use a vise and also you can secure with a bungee cord.
For the movable part of the impulse valve, sections of smaller pipe are cemented together. You can use the external part as a mold to get a near exact fit. When the movable part of the valve closes the holes in the external part, a water tight seal is formed. After the cement dries the piece is carefully marked. For this design the maximum width is 60 mm.
The movable part of the impulse valve is then trimmed on a table saw to the 60 mm. width. This is dangerous! Be careful! Next it is carefully centered and clamped inside the outside part of the valve. A 15/64 in. drill bit is used to drill the 2 holes on the left through both the outside and movable portion. After the movable portion is removed its holes are carefully enlarged using slightly larger bits. This way the movable part can slide on the center guide and pivot on a bolt. Note also that the movable part is marked for final trimming. The V shape on the left is the pivot point. The hole to the right is for an attachment of a weight.
Note that the movable part of the impulse valve pivots on a ¼ inch bolt and can drop approximately half an inch. Also note that the pipe used for the movable part is not completely smooth as is the pipe used for the outside part. It will be necessary to have a mostly smooth pipe for the outside so a good seal will be made. Pivot bolt Guide bolt Weight made from aluminum disc Note that the weight is attached with a special bolt which allows movable part to drop
The parts are held together either by PVC cement or by a clamp system made of high quality wood boards with holes made with hole saws and threaded rods or very long bolts. The joints in the photo on the left that are not cemented are indicated by arrows. In this example the delivery side of the ram pump is equipped with a fitting for 1 inch black plastic pipe. The wooden piece shown in the photo on the right is held by a section of PVC pipe split and cemented to the external part of the impulse valve. The snifter hole will be installed after we place the pump in the creek.
Hole for pivot bolt Hole for guide Plan for external part of impulse valve. It is made from 3 inch schedule 40 PVC. It is important to use pipe that is smooth on the inside. For drive heads less than 6 feet a drive pipe of 2 inches is best, for higher drive heads up to 10 feet or so use a 3 inch pipe.
Hole for impulse valve weight Plan for movable part of impulse valve. The pivot hole and hole for the guide are drilled with this part clamped to the inside of the outer part and enlarged with slightly larger drill bits. The external part of the valve needs to be smooth so when it contacts the internal part of the 3 inch pipe a good seal well result. .
I hope this information will prove usefull. There is much information on line. Some of the sites I found most usefull are listed below. http://www.eng.warwick.ac.uk/DTU/lift/ has 3 plans, very detailed information, very scientific http://www.bae.ncsu.edu/programs/extension/publicat/wqwm/ebae161_92.html has a table you can use to predict water use and delivery, more http://www.geocities.com/ResearchTriangle/System/7014/spanish has a plan for a unique design, also is in Spanish http:www.humboldt.com_extras/rampumps has a plan for making a pump using only standard plumbing parts Good luck in designing and making your own hydraulic ram pump.
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