Contrec 515 – GN14

Natural Gas Flow Computer (SGERG) - DP Meter (ISO/Cone)

The 515 GN14 application measures the volume, mass and gross heat content of natural gas. The instrument uses single or stacked differential pressure meters such as orifice plates, nozzles, venturi tubes or V-Cones as well as temperature and pressure sensor inputs.

The instrument calculates the flow according to differential pressure equations for the ISO 5167 or V-Cone meters. The flow calculations incorporate the conditions at which the flowmeter was calibrated and accurately account for thermal expansion effects.

The SGERG calculation (AGA-8 Gross 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 expotent, user entered values are used.


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

-8.0°C < t < 62°C P < 12MPa

17°F < t < 143°F P < 1740psia


Mflow = volume flow• 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