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  #1  
Old 10-19-2010, 04:09 PM
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FIMCO-MEISTER FIMCO-MEISTER is offline
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Water Hammers

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.
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Old 10-19-2010, 04:24 PM
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I'll give you hammer

If a 7 fps flow is cut down to 20 percent of that amount, then the hammer at closing is correspondingly reduced.
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  #3  
Old 10-19-2010, 04:29 PM
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FIMCO-MEISTER FIMCO-MEISTER is offline
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I agree 100% so try another hammer.

Actually you and I are on the same page. Only difference is terminology. I call it a slam and you call it a bump.
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Old 10-19-2010, 04:43 PM
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I just like that smiley. I'm used to banging pipes from dishwashers and washing machines, so it doesn't register as a calamity.
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Old 10-19-2010, 08:05 PM
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What kind of nails are used with water hammers?
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  #6  
Old 10-19-2010, 09:36 PM
Kiril Kiril is offline
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Quote:
Originally Posted by Wet_Boots View Post
I'll give you hammer

If a 7 fps flow is cut down to 20 percent of that amount, then the hammer at closing is correspondingly reduced.
Quote:
Originally Posted by FIMCO-MEISTER View Post
I agree 100% so try another hammer.

Actually you and I are on the same page. Only difference is terminology. I call it a slam and you call it a bump.
You are on the same page?

Quote:
Originally Posted by FIMCO-MEISTER View Post
So suggesting a slow closing valve makes for a kinder gentler water hammer is poppycock. Water hammers are design/installation issues.
The simple breakdown.

P = 0.070VL / t + Pi
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Old 10-19-2010, 10:17 PM
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Quote:
Originally Posted by Sprinkus View Post
What kind of nails are used with water hammers?
Liquid Nails
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  #8  
Old 10-20-2010, 12:35 AM
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Quote:
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Liquid Nails

are you using some sort of aqua logic?
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  #9  
Old 10-20-2010, 12:46 AM
Kiril Kiril is offline
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are you using some sort of aqua logic?
maybe a lava lamp?
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  #10  
Old 10-20-2010, 12:47 AM
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Quote:
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are you using some sort of aqua logic?
No, Aqua Velva.
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