Ag7 - Aga 7 Measurement Of Gas By Turbine Meters - Siemens 353 User Manual

Function Blocks

3.2.5 AG7 - AGA 7 Measurement of Gas by Turbine Meters

AG7 function blocks can be used on a one per loop basis.
This block uses the AGA 7 (American Gas Association
Report #7) calculation to accurately measure the volume
flow of gas at base conditions using a turbine meter. The
basic equations calculated by this block in accordance with
AGA Turbine Meter Report No. 7, 1985 (AGA Catalog No.
XQ0585) are:
Q = Q (T /T )(P /P )(Z
b f b f f b
Q
where: = volume flow at standard conditions
f
Q
= volume flow rate at base conditions
b
P
= flowing pressure (psia)
f
T
= flowing temperature)
f
Z
= compressibility at flowing conditions
f
P
= base pressure (psia)
b
T
= base temperature (°F)
b
Z
= compressibility at base conditions
b
Block output Q b is updated continuously and is the volume flow rate at base conditions in the same units as input
Q f . T b and T f are converted within the block from °F to °R (adds 459.67 to the °F input value) for the actual
calculation. Compressibility factors (
and downloaded from a host device, or calculated in the controller using the AG8 (AGA 8 Compressibility Factors
of Natural Gas) function block.
3-12
/Z )
b f
Z , Z
) can be entered manually using HLD (Hold) function blocks, computed
f b
P
f
Z
f,b
Application Diagram
AGA 7
Input Qf
Qf
Input Pf Pf
Input Tf
Tf
Zf
Input Zf
Input Zb Zb
P b
T b
P U T Q f
I N
I N P U T P f
N P U T T f
I
I N P U T
Z f
I U
N P T Z b
S N
E
T
Q
f
f
AGA 7
Q
b
UM353-1B
ESN = 000
AG7
AGA 7 Qb
Output Qb
base Pressure (psia)
.............................. Real (14.73)
base Temperature (deg F)
................... Real
INPUT Qf .............. loop tag.block tag.output
INPUT Pf ..............
loop tag.block tag.output
INPUT Tf ..............
loop tag.block tag.output
INPUT Zf .............. loop tag.block tag.output
INPUT Zb .............
loop tag.block tag.output
Exec. Seq. No. ..................... 000 to 250 (000)
April 2012
(60.0)
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