FLOW ELEMENT (Differential Pressure)

[AOC700]

Hi,

Which is the difference between next concepts when calculating Flow Rates across Orifice Plate-Standard. (Fuel Gas).

Diff. Pressure
Pressure Loss
Static Pressure

I´m checking a very old vendor datasheet and I do not see the difference between those concepts and which ones I have to use for recalculating the flowrate.

e.g.: (P1-P2) = Diff. Pressure or Pressure Loss????

Sizing criteria is according to ISO 5167-2003.

Thanks a lot.

 

[eduvillela]

I must agree with you when you say (P1-P2) = Diff. Pressure or Pressure Loss
I don't see why these two definitions would be different.

Static pressure is defined as the pressure measured by pressure gauges. The Total pressure is the sum of Static pressure and the velocity pressure.
But in the case of an orifice plate,the difference between the static pressure before and after the orifice will be the same as the pressure loss and the Diff. pressure.

 

[danw2]

The pressure loss associated with primary flow elements is sometimes referred to as 'permanent' pressure loss to distinguish it from the developed DP used as the flow measurement variable.

Not all the DP is permanently lost. There is some partial recovery, depending on the beta ratio.

The chart below shows permanent pressure loss for different types of primary flow elements at various Beta ratios.

 

[LittleInch]

This might help you

http://www2.emersonprocess.com/site...mentals-of-Orifice-Measurement-techWpaper.pdf

Basically the same as Danw2

Diff pressure is the difference in pressure difference immediately either side of the orifice plate. this provides your measurement when computed.

pressure loss is the pressure loss across the whole meter from say 5D upstream to 10D downstream. It should be less than the diff pressure as pressure recovers from the restriction, but is not zero.

Static pressure is static pressure, I.e. what is the "pressure" of the fluid you're measuring - 5 barg? 50 barg? 500 barg? Makes a difference.


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