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Gas Orifice Flow Meter Calculator

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Gas Orifice Flow Meter Calculator

This application calculates the flowrate through a large-diameter orifice using the approach outlined in ISO 5167 2:2003

Orifice meters use the pressure loss across a constriction (that is, the orifice plate) in a pipe to determine the flowrate.  

The formulas are valid for


pipes diameters between 50mm and 1000 mm,


and pressure ratios greater than 0.75.



Pipe Diameter D1 (m)

Molecular Weight

Orifice Diameter D2 (m)

Compressibility Factor

Upstream Pressure P1 (Pa)

Specific Heat Ratio

Downstream Pressure P2 (Pa)

Fluid Viscosity (Pa s)

Upstream Temperature (K)

Tap Type


 m3 s-1




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