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  #11  
Old 10-20-2010, 12:49 AM
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FIMCO-MEISTER FIMCO-MEISTER is offline
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Originally Posted by FIMCO-MEISTER View Post
Jess Stryker describes it well.


This works well, but leaves a minor engineering problem. It is very hard to get these valves to close slowly! Engineers have made some great progress but they still haven't fully defeated what I call the 80/20 problem. The 80/20 problem is that valves close slowly until they are about 80% closed, then they tend to snap fully closed in a millisecond! This causes the water in the pipes to suddenly stop moving. Now we all know the story of Jack and Jill, and the reason Jack fell down is that water is heavy (and perhaps Jack was paying too much attention to Jill , and not enough to his bucket, but I'm getting off-track here.) A column of water moving through the pipe at 7 feet per second carries with it a tremendous amount of weight and momentum. While it's not a perfect example, the one commonly used is to think of the water in the pipe as a big freight train going through a long tunnel. The valve closing is like blocking the end of the tunnel with thousands of tons of rock. When the train slams into the blocked end of the tunnel there is going to be one horrific crash! The faster that train is moving, the worse the crash will be. Thus the problem with water velocity in the pipe. The faster the water is moving, the worse the crash is going to be when the valve closes. That crash is the cause of a big thumping noise when the valve closes. Secondary thumps that follow are essentially "echoes" in the pipe.
Send Jess Stryker an e-mail Kiril and tell him your one formula theories.
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  #12  
Old 10-20-2010, 12:55 AM
Kiril Kiril is offline
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Originally Posted by FIMCO-MEISTER View Post
Send Jess Stryker an e-mail Kiril and tell him your one formula theories.
That would be her .... and those "theories" you so like to avoid have been empirically proven many times over ... and govern the very industry and products we all work with. But none of that matters to you ..... does it?
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  #13  
Old 10-20-2010, 12:59 AM
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FIMCO-MEISTER FIMCO-MEISTER is offline
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Well correct HER....... I'm not avoiding theories. I know a valve has two stages. The initial closing and the final slam shut. Are you claiming valves shut in one continuous motion?
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  #14  
Old 10-20-2010, 01:02 AM
Kiril Kiril is offline
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Originally Posted by FIMCO-MEISTER View Post
Well correct HER....... I'm not avoiding theories. I know a valve has two stages. The initial closing and the final slam shut. Are you claiming valves shut in one continuous motion?
Ahhhh ... now you are putting words in my mouth ..... nice.

P = 0.070VL / t + Pi

How does valve closing speed effect ...

1) Pressure
2) Flow
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  #15  
Old 10-20-2010, 01:08 AM
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Inspired Inspired is offline
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P x S to the tenth power = F
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  #16  
Old 10-20-2010, 01:13 AM
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One can appear smart without really being smart Kiril. If one keeps their design under 5fps and doesn't through poor installation methods cause situations when the flow can be much higher then water hammers won't be an issue.
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  #17  
Old 10-20-2010, 01:20 AM
Kiril Kiril is offline
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Originally Posted by FIMCO-MEISTER View Post
One can appear smart without really being smart Kiril. If one keeps their design under 5fps and doesn't through poor installation methods cause situations when the flow can be much higher then water hammers won't be an issue.
And you still avoid the simple equation that shows how wrong you are about valve closing/opening speeds.
But of course ... your experience negates the laws of physics ..... right?
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  #18  
Old 10-20-2010, 09:17 AM
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FIMCO-MEISTER FIMCO-MEISTER is offline
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Send Jess Stryker an e-mail and tell her that she is full of poppycock and that valve closings are one long smooth continuous event. I don't care about the first 80%. I only care about the final 20% which is what causes the problems.
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  #19  
Old 10-20-2010, 09:23 AM
Kiril Kiril is offline
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Originally Posted by FIMCO-MEISTER View Post
Send Jess Stryker an e-mail and tell her that she is full of poppycock and that valve closings are one long smooth continuous event. I don't care about the first 80%. I only care about the final 20% which is what causes the problems.
1) I never said Jess was full of shiit.
2) I also never said valves (solenoid) close in one smooth continuous event

Why exactly do you feel the need to put words in my mouth Pete?
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  #20  
Old 10-20-2010, 09:30 AM
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Then what installation methods do you believe exist to minimize the final 20% closing shock or do you believe any exist?

Can an irrigation system designed to not exceed 5fps because of installation methods create a situation in which it would exceed 5fps on opening?
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