I have made a calculation of an impending column-closure waterhammer. A
pumped return raises 20°C water in a 300 mm pipe into a receiver at a height
of 30 m above the level of the atmospheric tank from which the water is
drawn.
Prior to the event, the pump is off and the valve adjacent the upper tank
colsed to prevent the tank from draining back because the check valve at the
pump leaks.
Because atmospheric pressure cannot sustain a column of water over 10 m high
the leaking check valve aloows water to drain from the vertical column until
it is less than 10 m high.
This leaves a "void" between the face of the valve and the top of the
watercolumn.
To solve the problem an airvessel with a surface of 0.04 m2 and a height of
3 m with a waterlevel of 2.25 m and a gaspressure of 1.75 bara is
suffucient.
Van: Omid Hamlehdar [mailto:omid_7_ae@yahoo.com]
Verzonden: dinsdag 7 december 2004 6:06
Aan: <a href="/group/PipingDesign/post?postID=hQ_nhevmcTQRyQ9aBAiGmeRxirqbNPLL4p6K5QE_AKnyii51EwypYpmyQA9OJ0ioMNFKGEx1uXPkJJj21u5VJt-RpUIxfQ">PipingDesign@yahoogroups.com</a>
Onderwerp: RE: [PipingDesign] Surge Tank
Dear Erik
Thank you for your reply,
As I have mentioned it is a one way surge tank and so, I have modeled a swing check valve to prevent tank from draining back when pump is off.
As you mentioned Surge tank prevents a fluid column separation and rejoining but I have modeled a one way surge tank which is different as you know.
My concern is about this column separation, I suppose to locate an air valve (twin air valve from Erhard) to allow this air will be released, but I still want to know your opinion, do you think it is ok if air will enter to system after water has been finished in one way surge tank? Actually I have found that I need a huge amount of 800 cu meter to prevent air entering to system but it is impractical, I have decided to allow air enter to system after water has been finished in a smaller one way surge tank and locate an air valve to allow air released in re-starting.
Best regards
Omid
> What are the boundery conditions ?
> Is there a receiver at a height over 33ft above the
> level of the tank from
> which the water is drawn?
> Is there a valve a the end of the pipeline who
> closes to prevent the tank
> from draining back when the pump is off?
>
> A surge tank prevents a fluid column separation and
> rejoining.
>
> When air enters the pipe and the pump is restarted,
> the column of water will
> be accelerated into a partial empty pipe. Given a
> long anough void, the
> column of water can accelerate to its terminal
> velocity of perhaps 5 to 10
> fps before striking the valve face.
> Upon collision with the valve, the kinetic energy of
> motion is converted
> into potential energy by compressing the liquid.
>
> There should always be water in the surgetank.
>
>
>
>
>
> _____
>
> Van: Omid Hamlehdar [mailto:omid_7_ae@yahoo.com]
> Verzonden: maandag 6 december 2004 11:51
> Aan: <a href="/group/PipingDesign/post?postID=hQ_nhevmcTQRyQ9aBAiGmeRxirqbNPLL4p6K5QE_AKnyii51EwypYpmyQA9OJ0ioMNFKGEx1uXPkJJj21u5VJt-RpUIxfQ">PipingDesign@yahoogroups.com</a>
> Onderwerp: [PipingDesign] Surge Tank
>
>
> Hi everybody
>
> I have a question and will be pleasure to have your
> opinion.
>
> After analysis a pipe line for water transfer
> purpose,
> I found that I have extreme down surge, to suppress
> this surge I assumed a one way surge tank, my
> question:
>
> 1. Is it ok if air will enter in pipe line
> after water
> has finished in one way surge tank?
> 2. In terms of restarting (priming) the line,
> if air
> has entered to system, is there any consideration
> required regarding probable impact regarding column
> separation in line?
>
> Your contribution is highly appreciated
>
> Omid
>
>
>
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[Non-text portions of this message have been removed] Received on Wed Dec 08 13:46:00 2004
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