Geoff,
Thank you for saying that I am correct.
I know the non slam valves of Noreva very well. I installed a lot of those valves in the cooling circuits of a blast furnace.
But thy don’t close at zero velocity. There is still a reverse velocity but much less then with a swing check valve and that’s what makes them non slam valves.
See the attached graph showing the difference between a nozzle check valve and a swing check valve.
Erik
Van: <a href="/group/PipingDesign/post?postID=cwJLPxMB-GSVaLN71ZnD9-wmktVkNFaqlYDsTie6mG3jE_ZHY8BOCDtZyaf89TJ5XDdbQ5hh639t_W8iT4AauhSl3ZdOXA">PipingDesign@yahoogroups.com</a> [mailto:<a href="/group/PipingDesign/post?postID=cwJLPxMB-GSVaLN71ZnD9-wmktVkNFaqlYDsTie6mG3jE_ZHY8BOCDtZyaf89TJ5XDdbQ5hh639t_W8iT4AauhSl3ZdOXA">PipingDesign@yahoogroups.com</a>]
Namens Geoff Stone DD&D Australia
Verzonden: Friday, December 02, 2005 12:53 AM
Aan: <a href="/group/PipingDesign/post?postID=cwJLPxMB-GSVaLN71ZnD9-wmktVkNFaqlYDsTie6mG3jE_ZHY8BOCDtZyaf89TJ5XDdbQ5hh639t_W8iT4AauhSl3ZdOXA">PipingDesign@yahoogroups.com</a>
Onderwerp: RE: [PipingDesign] purpose of check valve
Erik,
You are correct.
In surge analysis the point at which the check begins to close is important and thats where confusion arises in your use of the term "closes". If there is flow of any amount technically there has to be an opening in the valve as miniscule as it might be. At zero flow the valve with heavy duty springs will be shut and the liquid column may not have reverse a velocity at the valve as it is closed! Instantaneous closure in practical terms. This what non slam valves aim to achieve. www.noreva.de.
Geoff
Erik Scheir <erik.scheir@pandora.be> wrote:
There is not one check-valve that closes at zero flow, not even the Tyco Keystone type 810 Check Valve.
I would suggest you to read the doc file and to have a look at the graphs.
One graph is showing the dynamic characteristics of different Check Valves, the other one is showing the behavior of an hydraulic dampened check valve during a pumptrip.
Regards,
Erik
Van: <a href="/group/PipingDesign/post?postID=cwJLPxMB-GSVaLN71ZnD9-wmktVkNFaqlYDsTie6mG3jE_ZHY8BOCDtZyaf89TJ5XDdbQ5hh639t_W8iT4AauhSl3ZdOXA">PipingDesign@yahoogroups.com</a> [mailto:<a href="/group/PipingDesign/post?postID=cwJLPxMB-GSVaLN71ZnD9-wmktVkNFaqlYDsTie6mG3jE_ZHY8BOCDtZyaf89TJ5XDdbQ5hh639t_W8iT4AauhSl3ZdOXA">PipingDesign@yahoogroups.com</a>]
Namens Arturo Murillo ( T Visa CLN )
Verzonden: Wednesday, November 30, 2005 7:06 PM
Aan: <a href="/group/PipingDesign/post?postID=cwJLPxMB-GSVaLN71ZnD9-wmktVkNFaqlYDsTie6mG3jE_ZHY8BOCDtZyaf89TJ5XDdbQ5hh639t_W8iT4AauhSl3ZdOXA">PipingDesign@yahoogroups.com</a>
Onderwerp: Re: [PipingDesign] purpose of check valve
Hello.
The check valves that have a spring on to the closing element (disk), do close al zero flow, so they are call waterhammer anticipation valves, there are numerous manufacturers of this valves.
Example: Tyco Keystone type 810 check valve.
Arturo Murillo C.
Tuberías Visa de Culiacán S.A. de C.V.
Culiacán, Sin. México
Tel: ( 667 ) 717 1801
> 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.
>
>
>
> _____
>
> Van: <a href="/group/PipingDesign/post?postID=cwJLPxMB-GSVaLN71ZnD9-wmktVkNFaqlYDsTie6mG3jE_ZHY8BOCDtZyaf89TJ5XDdbQ5hh639t_W8iT4AauhSl3ZdOXA">PipingDesign@yahoogroups.com</a> [mailto:<a href="/group/PipingDesign/post?postID=cwJLPxMB-GSVaLN71ZnD9-wmktVkNFaqlYDsTie6mG3jE_ZHY8BOCDtZyaf89TJ5XDdbQ5hh639t_W8iT4AauhSl3ZdOXA">PipingDesign@yahoogroups.com</a>]
> Namens r_ravoori
> Verzonden: Saturday, November 26, 2005 4:54 PM
> Aan: <a href="/group/PipingDesign/post?postID=cwJLPxMB-GSVaLN71ZnD9-wmktVkNFaqlYDsTie6mG3jE_ZHY8BOCDtZyaf89TJ5XDdbQ5hh639t_W8iT4AauhSl3ZdOXA">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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