Contrec 515 – GN05

Natural Gas Flow Computer (AGA - 8) - DP Meter (AGA - 3)

The 515 GN05 application measures the volume, mass and gross heat content of natural gas. The instrument uses single or stacked differential pressure inputs, as well as temperature and pressure sensor inputs.

The instrument calculates the flow according to AGA-3 differential pressure equations. The flow calculations incorporate the conditions at which the flowmeter was calibrated and accurately account for thermal expansion effect.

The AGA-8 Detail Characterization Method is used to obtain accurate values of density and compressibility factors for the flow calculations. For other gas properties, such as viscosity and isentropic exponent, the AGA-3 recommended values are used.


The gas density and compressibility factor calculations are based on the AGA-8 equations. The calculations are valid for the region:

-130°C < t < 400°C P < 280MPa

-200°F < t < 760°F P < 40000psia


volume flow =Mflow/ρflow

corrected flow = Mflow/ρ ref

Heat flow = Mflow•Hm


Mflow = mass flow

ρflow = density at flow conditions

ρ ref = density at reference conditions

Hm = mass gross heating value