Ram Pump Problem

[noblelivestock]

I'm installing another homemade ram pump.

The first went w/o a hitch.  Easy to start up,

and just pumps away w/a steady thunk, thunk, thunk.



The second was built exactly like the first.

This son-of-a-gun however is hard to start,

and once it's running, the the clacker valve

will accelerate.  Slowly at first -- then faster

and faster until it becomes irratic and stops.

The water pressure has the clacker shut tight.



Maybe because I'm a bit frustrated right now,

but I cannot work out the problem.  The valve

ought to drop like a stone when the pressure

equalizes, right?

[scottsAI]

Maybe this will help you.

What would happen if the air space filled up with water?

Air leaked out.

Have fun,

Scott.

[Flux]

You give almost nothing to go on. It is normal for the drive water pressure to hold the waste valve ( clacker) shut.

Some of those self build designs using plumbing bits don't look very inspiring and may need a certain amount of experiment is your drive head is low or the delivery head is low in relation to the drive, but even so Rams are not very critical and as long as you keep the basics right it should work.

I assume that these are under identical heads, but if they are on different sites or with different conditions there may be reasons for the trouble.

If you have a drive head less than 3ft you may need to do some experimenting but I have got Rams to run at 18" drive head.

It is absolutely essential that the drive pipe is completely air tight and has no upward air traps ( even glove valves in the drive pipe can cause air locks). Most difficult to explain problems come down to drive pipe troubles.

Similarly as Scott said you must have and be able to maintain an air supply in the air vessel. You must also make sure that the air doesn't increase to the point where it displaces the water from the delivery valve. The delivery valve must also close completely for the thing to work. The recoil wave needed to open the waste valve is initiated by the closing of the delivery valve and any failure of that to seat will result in failure with waste valve closed.

Thoroughly check the drive pipe, check for air in the air vessel, check for absolute certainty of closure of the delivery valve and be certain that the delivery head is large in relation to the drive head. If it is less than 7 times you may have to mess with loading of the waste valve. To prove this point, block the outlet and see if it runs reliably.

Flux

[thirteen]

possible blockage on the discharge line, half closed shutoff valve, or is each one is on a seperate line or could they meet somewhere in your system back preasure to the new one. Just some ideas.

[noblelivestock]

I thought about what you said.  I had put an air bladder in the air chamber when I made the pump.   Nevertheless, I took the air chamber off the pump and checked it for leaks, using an air compressor I pumped the air pressure up to 110 psi, then checked the pressure a couple hours latter.  Didn't lose a single pound.  Remounted the air chamber, pressured the whole pump (not so easy) with the same results.  So the pump is tight, at least to best I'm able to test.

[jimovonz]

This will occur if the ram pump flows more water than is available. The level in the drive pipe will slowly fall until there is not enough head to maintain operation. You need a smaller clack valve or more water. Depending on the orientation of the valve, you can try tipping it over so that it needs less water flow to close it. This will cause it to cycle more quickly and flow less water. There are other ways of regulating the valve but you haven't been very specific on your setup. I use magnets on mine to regulate the cycle speed http://www.fieldlines.com/story/2007/6/12/21931/9477.

Being hard to start is typical until there is enough delivery head to create a sufficient water hammer effect that causes the water in the drive pipe to bounce back and suck open the clack valve to repeat the cycle.

[noblelivestock]

I just posted a reply to scott and it was placed under flux's post.  I'm not sure why.  

Anyway ... flux ... ah, where to start.  Well, I started with the easy stuff first.  I checked the delivery valve and the waste (clacker) valve.  As I posted to scott, I checked the air chamber for leaks.


Next I swapped out the ram pumps.  My logic: I made them identically so if it's a site problem, the working pump ought to have the same problem as its sister pump.  It did, and the sister pump works just fine at the other site.

I decided to get a big thermos of coffee a chair and just watch -- no fiddling with anything -- just observe.  Yogi Berra was so right ... you can see a lot by just looking.  Bubbles.  The drive pipe was purged of air each time I connected everything up.  The trouble is that the drive pipe was flowing so fast that it was sucking air down the pipe.  This is about 10 feet of head and 40 feet of pipe.  I didn't think that was possible.

So yeah, I rearranged some things so entry point for the drive pipe was much deeper under the surface.  If it sucks air now, I'll have to have a pint or two and call a neighbor or two over because nobody will believe me.

The pump has been running smoothly for hours.  I'll check it again in the morning.  

I did block the outlet -- no delivery pipe -- to both pumps.  Just a valve cover that came with the valve.  I knew the pump had a maximum height it could pump, but I didn't know it had a minimum.  flux, if the delivery head is less than seven times the drive head, do I restrict the flow to the waste valve so the momentum is less?  The first site has about 45 feet of drive head and the delivery head is definately less than 315 feet so I'm little concerned how I proceed.

[Flux]

Sometimes posts do turn up in strange places here if you try to reply to a specific one, I find it annoying but it seems a fact of life and it can be confusing.

I think Jimovonz has hit it, you are over running the supply, it will stop instantly the drive pipe draws in air. With simple valves you may not have a lot of control of the flow, I am not sure what valves you have. Normally altering the stroke of the waste valve will cover a considerable flow range.

If you try to use flow rates too low for the drive pipe size the results are poor so if you have to reduce waste valve size drastically you may need a smaller diameter drive pipe.

If the delivery head is too low you can artificially increase it with a partly closed gate valve in the delivery.

I can get them to run with a delivery head about 3 or 4 times the drive head but that is not with simple plumbing fittings as valves.  I must look at jimovonz's magnetic control, I have considered it and my tricks with springs probably does exactly the same thing. With decent valves and sufficient control you can get away with lower drive heads and lower ratios of delivery to drive. With simple non adjustable valves you have more constraints.

Sort out your water use and you should be ok.

Flux

[scottsAI]

noblelivestock,

Darn, did not think of sucking air!

Glad to hear you figured it out.

I can find no reference to a minimum head on the output other than it should be 1 foot higher than the input? If not higher than what do you need the pump for!

7x is considered the practical limit of input head to output head.

Design considerations on drive pipe diameter to length min / max (half way down page)

http://www.clemson.edu/irrig/equip/ram.htm

How ram pump works for others:

http://www.clemson.edu/irrig/equip/ram4.htm

Have fun,

Scott.

[Flux]

Not sure where you got this data. you will never get a ram to keep running with only 1ft difference between drive and delivery head. With low heads you will have to have careful control of the waste valve to get it to run with less than 3:1. At higher heads you may manage 3:1 with simpler valves.

With non adjustable valves you may need 7:1 to keep it running at heads below 4ft drive.

Ratios of up to 20:1 are common and the limit is way over this at low efficiency.

Flux

[scottsAI]

Thanks Flux,

Not sure where I got the 7x from, read about it some where. Remembered it as practical, like you said higher ratio are not efficient?-)

I researched it and see 20x and higher is possible! Very cool. Thanks.

1 foot higher on the output, why do anything less?

http://www.clemson.edu/irrig/equip/ram.htm

Paragraph labeled: Valve Operation Descriptions

The swing check valve (part 4 - also known as the impetus valve) can be adjusted to vary the length of stroke (please note that maximum flow and pressure head will be achieved with this valve positioned vertically, with the opening facing up). Turn the valve on the threads until the pin in the clapper hinge of the valve is in line with the pipe (instead of perpendicular to it). Then move the tee the valve is attached to slightly away from vertical, making sure the clapper hinge in the swing check is toward the top of the valve as you do this. The larger the angle from vertical, the shorter the stroke period (and the less potential pressure, since the water will not reach as high a velocity before shutting the valve). For maximum flow and pressure valve #4 should be in a vertical position (the outlet pointed straight up).

Therefore just over 1x is possible too!

Does this agree with you?

Have fun,

Scott.

[Flux]

Interesting. I have never tried any form of swinging clack valve so can't comment.

If you can get down to 1ft above drive head it could be very useful in some applications. I have had only limited success working with drive heads below 18" but if you could get it reliably down to 1ft drive the ratio would then be 2:1 and that is possible with care.

The standing wave needed to reverse the flow in the drive pipe needs to come from doing work on the delivery side, it may be that using rather inappropriate delivery valves will provide this with lower ratios, so part of this success may also be related to the delivery valve chosen.

Flux

[noblelivestock]

I know this is a bit late, but here are a couple of photos of one of the ram pumps in question.






I had to put a gate valve to lower the water pressure for the pump at the site with the larger head too.   Too much drive head for the delivery head ... what a problem to have, huh?  May I ought to relocate the pump and start working on a micro-hydro project for the remaining head.

[Flux]

That is one of the problems with working with unsuitable valves. I don't like the idea of restricting the drive supply with a gate valve, in fact I would never have considered it, it will cause many problems. Also I see that you have plastic drive pipe and again this only works reasonably well at low drive heads. The elasticity of the pipe will seriously affect the operation, reducing the effective head to which it will pump and it will reduce the recoil wave needed to open the waste valve during each cycle.

If you need to go a long way to get the drive head then it is infinitely better to use a larger plastic pipe to feed a small tank at the drive head with a decent steel drive pipe running down to the ram at 45 deg. It doesn't have to be very long, there is a lot of myth about all this, but to keep it very short you will need better valves than plumbing fittings. Even with your fittings as valves I doubt that you need more than 20ft of drive pipe.

Rams are very simple and incredibly effective but if you don't understand their peculiarities they can produce strange problems and many are almost certainly not working at their best because of errors in design and installation.

Flux

[noblelivestock]

flux, thank you very much for helping me work through a frustrating problem.  I know you mean well but your last post but it is more in the realm of the ideal vice the practical .. at least for me.

For less than 1/1000th the cost of even a low-end commercially manufactured ram pump -- professionally installed, I have two less-than-ideal, amateurishly-made-and-installed ram pumps.

Bottomline: I've water pumping up to the top of the hill.  Will the pumps cause me trouble in the future?  There's no doubt in my mind, but that's life at the lower end of the social-economic ladder.  I have a 25-year-old truck (that runs well) ... practical, not ideal.

After having said all that, I must say: Thank You! I sincerely mean this: your help (and Scott's too) was invaluable.  Without it, I may have stewed over the problem for weeks before getting the kinks worked out.