Valve outlet area

Please help me with this

Fisher Specification Manager requires Valve Outlet Area for calculating the velocity, I am selecting a 2" globe valve in 6" pipe size for gas application, but I do not know where to get exactly the data

I was looking for "Help By Screen" in FSM but i only found "flow areas" is the same?

If I select a 2" valve (with 2.8 square inch area) the velocity is critical...

Please help me whit this

Thanks in advance

  • Javier,
     
    Please review line size versus valve size you think you want.  6 to 2  (3 to 1 ratio) is frowned upon in the pipe/valve world.
     
    2 to 1 ratio seems to be what the industry will tolerate, no more.
     
    Suggest looking at a 3” valve if you are stuck on 6” piping
     
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  • In reply to Eric Sanborn:

    Thanks Eric
    This is very useful.
    but I am looking for the valve outlet area, I need to be sure to use the data for the fluid velocity
  • Javier, the flow area from your Specification Manager “Help by Screen” is the correct site for both valve and pipe area, there are several links, see below.  As Eric mentioned, you don’t want to be less than 2:1 Pipe to Valve body size ratio.
     
    You should select a 3” valve and use reduced trim if needed to keep in a good Cv range.  In a 3” E body, the area is 7.1 in2 and should solve your velocity issue.
     
    Regards,
     
    __________________________________________________________________________
    Craig Jeane

    Puffer-Sweiven
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  • In reply to Craig Jeane:

    Thanks Craig

    This is very useful.
    I will change the valve size.

    Regards
  • Hello what is Cv for the valve?
  • In reply to prane11:

    Hi Prathamesh,

    As defined in the Control Valve Handbook, Cv is a coefficient related to the geometry and flow area of a valve. It is used in valve sizing to establish flow capacity at given travel points. The actual Cv number refers to the number of U.S. gallons per minute of 60 degrees Fahrenheit water that will flow thru the valve with a one pound (PSI) pressure drop. For further learning on this and other control valve topics, I suggest reading the Control Valve Handbook and consider enrolling in the control valve courses offered by Emerson Educational Services. Links to both are below.

    http://www.documentation.emersonprocess.com/groups/public/documents/book/cvh99.pdf
    http://www2.emersonprocess.com/en-us/brands/edservices/fielddevices/controlvalves/pages/controlvalvetraining.aspx

    You may also want to check out the Train & Develop group here on EE365: http://community.emerson.com/process/emerson-exchange/solveandsupport/trainanddevelop

    Regards,

    Jake Walahoski
    Engineering Instructor, Fisher Product Training
  • In reply to Javier:

    The easiest way to calculate flow area is simple. It is a circular outlet of say 3 Inch diameter. therefore the flow area is the area of circle which is (PI(3.14)*D*D)/4 In this case (3.14*3*3)/4 is 7.06 In2 which is approx rounded to 7.1In2. can be applied to any circular outlet flow area calculation.