Salmon fishing & fly tying on the Miramichi...

Saturday, 12 May 2012

Hydraulic Ram Pump

Dad mentioned this might be a good thing to look into for the Den....

(this is borrowed content and I hope the original author doesn't mind: http://www.clemson.edu/irrig/Equip/ram.htm#Plans )


The more I read about it the more I agree. It looks like a great way to pump water while being off the grid...

How a Hydraulic Ram Pump works

The concept behind the ram idea is a "water hammer" shock wave. Water has weight, so a volume of water moving at a certain speed has momentum - it doesn't want to stop immediately. If a car runs into a brick wall the result is crumpled metal. If a moving water flow in a pipe encounters a suddenly closed valve, a pressure "spike" or increase suddenly appears due to all the water being stopped abruptly (that's what water hammer is - the pressure spike). If you turn a valve off in your house quickly, you may hear a small "thump" in the pipes. That's water hammer.
Here's how the hydraulic ram pump actually works, step-by-step:
(1) Water (blue arrows) starts flowing through the drive pipe and out of the "waste" valve (#4 on the diagram), which is open initially. Water flows faster and faster through the pipe and out of the valve. (Click here to see an actual image of an operating ram pump for this step.)
(2) At some point, water is moving so quickly through the brass swing check "waste" valve (#4) that it grabs the swing check's flapper, pulling it up and slamming it shut. The water in the pipe is moving quickly and doesn't want to stop. All that water weight and momentum is stopped, though, by the valve slamming shut. That makes a high pressure spike (red arrows) at the closed valve. The high pressure spike forces some water (blue arrows) through the spring check valve (#5 on the diagram) and into the pressure chamber. This increases the pressure in that chamber slightly. The pressure "spike" the pipe has nowhere else to go, so it begins moving away from the waste valve and back up the pipe (red arrows). It actually generates a very small velocity *backward* in the pipe. (Click here to see an actual image of an operating ram pump for this step. Note the drops of water still falling to the ground in the image.)
(3) As the pressure wave or spike (red arrows) moves back up the pipe, it creates a lower pressure situation (green arrows) at the waste valve. The spring-loaded check valve (#5) closes as the pressure drops, retaining the pressure in the pressure chamber.

(4) At some point this pressure (green arrows) becomes low enough that the flapper in the waste valve (#4) falls back down, opening the waste valve again. (Click here to see an actual image of a ram pump for this step.)

(5) Most of the water hammer high pressure shock wave (red arrows) will release at the drive pipe inlet, which is open to the source water body. Some small portion may travel back down the drive pipe, but in any case after the shock wave has released, pressure begins to build again at the waste valve (#4) simply due to the elevation of the source water above the ram, and water begins to flow toward the hydraulic ram again.
(6) Water begins to flow out of the waste valve (#4), and the process starts over once again.
Steps 1 through 6 describe in layman's terms a complete cycle of a hydraulic ram pump. Pressure wave theory will explain the technical details of why a hydraulic ram pump works, but we only need to know it works. (One American company has been manufacturing and selling hydraulic rams since the 1880’s). The ram pump will usually go through this cycle about once a second, perhaps somewhat more quickly or more slowly depending on the installation.
Each "pulse" or cycle pushes a little more pressure into the pressure chamber. If the outlet valve is left shut, the ram will build up to some maximum pressure (called shutoff head on pumps) and stop working.
The ram is quite inefficient. Usually 8 gallons of water must pass through the waste valve for each 1 gallon of water pumped by the ram. That is acceptable for a creek or river situation, but may not be a good option for a pond that does not have a good spring flow.

(Page and images copyright 2007 Bryan Smith. All rights reserved.)

Original link:::: http://www.clemson.edu/irrig/Equip/ram4.htm

PLANS
This information is provided as a service to those wanting to build their own hydraulic ram pump. The data from our experiences with one of these home-made hydraulic ram pumps is listed in Table 4 near the bottom of this document. The typical cost of fittings for an 1-1/4" pump is currently $120.00 (U.S.A.) regardless of whether galvanized or PVC fittings are used.


Table 1. Image Key

1 1-1/4" valve 10 1/4" pipe cock
2 1-1/4" tee 11 100 psi gauge
3 1-1/4" union 12 1-1/4" x 6" nipple
4 1-1/4" brass swing check valve (picture) 13 4" x 1-1/4" bushing
5 1-1/4" spring check valve 14 4" coupling
6 3/4" tee 15 4" x 24" PR160 PVC pipe
7 3/4" valve 16 4" PVC glue cap
8 3/4" union 17 3/4" x 1/4" bushing
9 1-1/4" x 3/4" bushing

All connectors between the fittings are threaded pipe nipples - usually 2" in length or shorter. This pump can be made from PVC fittings or galvanized steel. In either case, it is recommended that the 4" diameter fittings be PVC fittings to conserve weight.

Conversion Note: 1" (1 inch) = 2.54 cm; 1 PSI (pound/square inch) = 6.895 KPa or 0.06895 bar; 1 gallon per minute = 3.78 liter per minute. PR160 PVC pipe is PVC pipe rated at 160 psi pressure.

Click here to see an image-by-image explanation of how a hydraulic ram pump works

Click here to see a short mpeg movie of an operating ram pump
(Note - this is a 6.2 mb movie clip. On slower systems (11 mbps, etc.), it will load "piece-meal" the first time. Allow it to finish playing in this fashion, then press the play button again to see it in full motion with no "buffering" stops. Dial-up users may have to download the file to see it - simply right-click on the link, then select "Save Target As..." to save it to your computer. Downloading may take considerable time if you are on a slower dial-up system.)

Assembly Notes:

Pressure Chamber - A bicycle or "scooter tire" inner tube is placed inside the pressure chamber (part 15) as an "air bladder" to prevent water-logging or air-logging. Inflate the tube until it is "spongy" when squeezed, then insert it in the chamber. It should not be inflated very tightly, but have some "give" to it. Note that water will absorb air over time, so the inner tube is used to help prevent much of this absorbtion. You may find it necessary, however, to drain the ram pump occasionally to allow more air into the chamber. (The University of Warwick design (link below, pages 12-13) suggests the use of a "snifter" to allow air to be re-introduced to the ram during operation. Their design, however, is substantially different from the one offered here and provides a location (the branch of a tee) where the addition of a snifter is logical. This design does not. Also, correctly sizing the snifter valve (or hole as the case may be) can be problematical and may allow the addition of too much air, resulting in air in the drive pipe and ceasing of pumping operation. For these reasons we have elected not to include one in this design.)
According to information provided by the University of Warwick (UK) ( http://www.eng.warwick.ac.uk/dtu/pubs/tr/lift/rptr12/tr12.pdf , page 14), the pressure chamber should have a minimum volume of 20 times the expected delivery flow per "cycle" of the pump, with 50 times the expected delivery being a better selection. The chart below provides some recommended minimum pressure chamber sizes based on 50 times the expected delivery flow per "cycle." Note that larger pressure chambers will have not have any negative impact on the pump performance (other than perhaps requiring a little more time to initially start the pump). Some of the lengths indicated are quite excessive, so you may prefer to use two or three pipes connected together in parallel to provide the required pressure chamber volume. Well pump pressure tanks will also work well - just make sure they have at least the minimum volume required.