Function Blocks
AGA8GS Function Block
22 HC900 Hybrid Control Designer Function Block Reference Guide Revision 11
2/07
AGA8GS Function Block
Description
The AGA8GS label stands for Gas Compressibility Gross Method AGA8 Calculation
METER BLK
CONNECT
This block is part of the Calculations category.
Function
The Gross method is used to approximate natural gas by treating it as a mixture of three components,
equivalent hydrocarbon component, Nitrogen and Carbon Dioxide. It is typically used for dry, sweet
(no H
2
S) natural gas. There are two methods used:
Gross Method 1 calculates the super-compressibility and gas density from knowledge of the relative
density, heating value and carbon dioxide, hydrogen and carbon monoxide components.
Gross Method 2 calculates the super-compressibility and gas density from knowledge of the relative
density, Nitrogen, carbon dioxide, hydrogen and carbon monoxide components.
The Gross Method only works over a limited range of conditions but requires less instrumentation to
implement.
Inputs
TF = Temperature at flow in units selected by the UNITS configuration parameter.
PF = Pressure at flow in units selected by the UNITS configuration parameter.
HW = Differential pressure in the units selected by the UNITS configuration parameter. (Only required if
the meter block is AGA3.)
CO2 = Carbon Dioxide Mole Fraction
HYD = Hydrogen Mole Fraction
CO = Carbon Monoxide Mole Fraction
NITRGN = Nitrogen Mole Fraction (Method 2 only)
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