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TCV & Globe Valves

Hello

According to Help, What ‘Throttle Control Valve’ control is minor losses, but minor losses are controlled by Globe Valves. What is difference between TCV and Globe Valve?

Sim

  • Sim,

    I think I understand your question. In WaterGEMS, a throttle control valve has the ability to simulate minor losses with headloss characteristics that change over time. This can be done using a discharge coefficient, headloss coefficient, or valve characteristics curve. The valve type property of the TCV, which includes globe valve as an option, allows you to specify the type of TCV valve you are modeling. The other choices for this valve type of butterfly, needle, circular gate, ball, and user defined.

    I hope that helps.

    Mark

    Mark

    Answer Verified By: Sushma Choure 

  • Further to what Mark said, I will add that the selection made from the "Valve Type" field for a TCV (butterfly, globe, etc) allows the program to relate "relative closure" (%) to a discharge coefficient, based on the entered "fully open discharge coefficient". This is used with the Valve Characteristic Curve type.

    So, a TCV is basically a type of node element that you can use to model various types of valves, including a "globe" valve. A globe valve could be modeled with a TCV by simply entering a single known headloss coefficient for example, based on the position of the globe valve that you are simulating. Or, you could go into further detail by entering the "fully open discharge coefficient" and selecting Globe as the valve type. You'll then be able to enter the position of your valve (either initial or on a relative closure pattern for EPS) in terms of percent closed, and the program will determine the discharge coefficient to use based on the fully open discharge coefficient along with a typical Globe valve relationship (see chart below) for that particular percent closure value. 


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.

    Answer Verified By: Sushma Choure 

  • Dear Jesse

    Let me know from where you got this chart? It needs to explain more about. What is t/tc?

    Sim

  • The chart is based on Fok, A.T.K., “A Contribution to the Analysis of Energy Losses in Transient Pipe Flow”, Ph.D. Thesis, University of Ottawa, 1987.

    T/Tc is time over time to fully close (so 0.5 would mean 50% closed/"stroke") and A/Ao is area over full area (which can be correlated to discharge coefficient). Basically it shows the relationship between stroke and discharge coefficient. Meaning, one particular valve will have a different flow control characteristic when closed half way versus another type of valve.

    If your particular valve doesn't align with these relationships, you always have the option to choose "user defined" as the valve type, then enter your own relationship between %closed and %discharge coefficient. Or, you could of course enter valve positions the traditional way using headloss coefficient or Discharge coefficient instead of %closed.


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.

  • Hello Jesse

    1- I always do consider 'Discharge Coefficient' as 'Emitter Coefficient'. These two coefficients are exactly the same. Are not? When is 'Discharge Coefficient' used and when is 'Emitter Coefficient'?

    2- How do you make correlation between 'Area' and 'Discharge Coefficient' in the chart?

    3- I wonder if you explain this question that how is correlated Flow (Instead time) and Area? For in-line valves (I mean valves which do not discharge to atmosphere) and discharge valves which discharge flow to atmosphere. Do we derivate Flow-Area graph from this chart?

    Thankx

    Sim