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Re: Check Valves


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Posted by BoilingMan on May 24, 2002 at 06:42:06:

In Reply to: Re: Check Valves posted by Tony Conner on May 24, 2002 at 05:20:37:

: For anyone interested, this is what Crane says:

: "Most of the difficulties encountered with check valves, both lift and swing types, have been found to be due to oversizing which results in noisy operation and premature wear of moving parts.

: Sizing of check valves in accordance with the specified minimum velocity for full disc lift will often result in valves smaller in size than the pipe in which they are installed; however the actual pressure drop will be little, if any, higher than that of a full size valve which is used in other than the wide open position. The advantages are longer valve life, and quieter operation."

: Since I stopped blindly installing or replacing checkvalves with line size valves (particularly in view of the fact that most piping is grossly oversized to begin with), I've found that their lifespan has increased greatly. And in constant circulation systems, like hot water heating, or chilled water lines, correctly sized checks eliminate the annoying "tinkling" noise the occupants complain about.

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Well, itís interesting discussion.
What is my opinion. If you are familiar with Grudfos pump design, the impeller stack is very light, and when pump stops, there is no inertia, so pressure drops almost immediately, creating quick backflow from the boiler, which in turn forces the disk hit against the seat plus sending a little blast of high pressure water back to the feeding line. Sounds right?

Question: if feed water T* is 220*F and steam pressure in the boiler is 100 PSI Water temperature in the boiler is about 330-350*F.
Could the difference about 100*F produce enough (if any)flush steam for hammering?

BTW about water hammer arrester. I was talking about sealed factory precharged type like HYDRA-RESTER look at www.siouxchief.com.




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