Re: purpose of check valve

Just another point - Hoerbiger Corp. makes a "check" valve which is essentially a compressor valve sandwiched between a couple of flanges. This has a VERY quick open/closing time - like milliseconds. Problem is, to get acceptable flow area, the diameter of the valve assembly is large, compared to the pipe diameter. But is great for pulsating/reversing flows.

George Mckinney
Augusta Engineering & Design
----- Original Message -----
From: "Geoff Stone DD&D Australia" <blenrayaust@yahoo.co.uk> To: <PipingDesign@yahoogroups.com> Sent: Wednesday, November 30, 2005 4:49 PM Subject: RE: [PipingDesign] purpose of check valve

> Spring loaded or counterweighted check valves can close before flow
reversal. It depends upon the strength of the springs and size of the counterweight. Its just a balance of forces thing.
>
> General practice though is that the spring stiffness or counterweights
are sized to close quickly but not so to create such a pressure drop as to impact on energy costs.
>
> Noreva non slam check valves are designed to close in <0.4secs. The mass
of the moving parts is low and this is how this type of valve achieves a reduction in waterhammer positive pressures as it does. www.noreva.de.
>
> The dynamic characteristics of a check valve should be provided by the
manufacturer so that this information can be used in a surge analysis.
>
> If you want a very fast closing valve actuated valves using nitrogen fom
a gas bottle has been used on gas and liquid lines in the past.
>
> Geoff
>
> Erik Scheir <erik.scheir@pandora.be> wrote:
> As far as I know there are no check valves who closes before flow
reverse.
> An ideal check valve would close at zero flow (working like a diode).
>
> But ideal does no exist, so check valves always closes at return flow. The
> fast a check valve closes, the best it is with respect to waterhammer.
>
>
>
> If you know such check valves please let me know the type and the
> manufacturer.
>
>
>
> Erik.
>
>
>
> _____
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> Namens r_ravoori
> Verzonden: Saturday, November 26, 2005 4:54 PM
> Aan: <a href="/group/PipingDesign/post?postID=yOGbBIDxk80lKtdWsFCEyVz6EY3vWtxwKlOM7Yq1t9pK9Ojrg-2W6Jse3oKNgFcLPtWZMFD-qEBTxTg1rDcpsQZgZw">PipingDesign@yahoogroups.com</a>
> Onderwerp: [PipingDesign] purpose of check valve
>
>
>
> Apart from back-flow prevention, there are other uses:
> 1) Spring loaded or 'silent' check valves assist in minimizing water
> hammer effects by the fast closure of the valve before flow reverses.
> 2) There are other specialized check valves used in steam extraction
> lines from turbines. These are power-assisted and prevent water from
> entering the turbine.
> R.V.Ramachandran
>
>
>
>
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Received on Thu Dec 01 08:12:00 2005