Fully Developed Flow Past Orifice Plate: 20-40x Diam.

[Isoho]

Hi!

what is the distance that a fluid has to go to become fully developed flow past an orifice plate pressure meter?

I have read somewhere that it is 20 to 40 times the diameter of the constriction. Is this correct?

 

[FredGarvin]

The standard one has to follow for printed calculations to be valid is 15 diameters of the pipe ID, not the orifice diameter, downstream before any kind of disruption or change in flow path for. This does depend on beta ratio however. There is a table in the ASME specs that spells this out and gives the ranges required.

 

[Isoho]

Thanks Fred!

I was wondering where you sourced that information from as I have just been on the ASME website and found a few papers relating to the matter but I was unable to find the table that you mention? (my beta number is 0.66). I would also really like to read up on the factors behind the 15D if you have any web links to how you know that.

Thank you for your help already though!

 

[FredGarvin]

The two main specs that cover this from ASME are

http://catalog.asme.org/Codes/PrintBook/MFC3M_2004_Measurement_Fluid.cfm
http://catalog.asme.org/Codes/PrintBook/MFC14M_2003_Measurement_Fluid.cfm

There are other sources for flow criteria, but these are the main ones from my neck of the woods. API, AGA, ISO and others all have variations on the same theme.