Ag3 - Aga 3 Orifice Metering Of Natural Gas - Siemens 353 User Manual

Function Blocks

3.2.4 AG3 - AGA 3 Orifice Metering of Natural Gas

AG3 function blocks can be used on a one per loop basis. This
block uses the AGA 3 (American Gas Association Report #3)
calculation to accurately measure the flow of natural gas using
an orifice meter with flanged taps. The basic equations
calculated by this block, in accordance with AGA Report No. 3,
Orifice Metering of Natural Gas, Part 3, November 1992 (AGA
Catalog No. XQ9210), are:
= C' √ P
Q h
b f1 w
C' = F (F +F )Y F F F
n c sl 1 pb tb
Q
where: = volume flow rate at base conditions
b
C'
= composite orifice flow factor
P
= absolute flowing pressure(upstream tap)
f1
h
= orifice differential pressure
w
F
= numeric conversion factor
n
F
= orifice calculation factor
c
F
= orifice slope factor
sl
Y
= expansion factor (upstream tap)
1
F
= base pressure factor
pb
F
= base temperature factor
tb
F
= flowing temperature factor
tf
F
= real gas relative density factor
gr
F
= supercompressibility factor
pv
Q
Output is updated every scan cycle. Output
b
for other effects. The following conditions are considered in the calculations:
•
Standard Conditions are:
•
Nominal pipe size is 2" or larger, Beta is 0.1 - 0.75, and Re (Reynolds Number) is 4000 or larger.
•
Y
(expansion factor) and absolute flowing pressure
•
h
is in inches H 0 and
w 2
The following parameters are configuration entries:
d
= orifice plate bore diameter in inches at a reference temperature of 68°F
r
D
= meter tube internal diameter in inches at a reference temperature of 68°F
r
P
= base pressure (psia)
b
T
= base temperature (°F)
b
The following are analog inputs to the AGA 3 function block:
h
= orifice differential pressure (in H
w
P
= flowing pressure at upstream tap -
f
T
= flowing temperature (°F)
f
G
= real gas relative density (specific gravity)
r
3-10
F F
tf gr pv
C'
is updated continuously for temperature effects and periodically
P T
= 14.73 psia, = 60°F,
s s
P h
is in psia. 0 < [ /(27.707*
f w
O)
2
P
AGA 3
Input hw hw
Pf
Input Pf
Input Tf
Tf
Input Gr Gr
Input Zs Zs
Zf
Input Zf
Input Zb Zb
d r
D
P b
T b
m
P L A T E
N P U T h w
I
I N P U T P f
I N P U T T
N P U T G r
I
I N P U T Z
I N P U T Z
I U
N P T Z b
S
E
Z
sair = 0.999590.
P
are referenced to upstream tap (i.e.
f
P
)] <= 0.2.
f
(psia)
f1
UM353-1B
ESN = 000
AG3
AGA 3 Qb
Output Qb
C'
Output C'
diameter ref.
for plate (inches) .................... Real
r
Diameter ref.
for tube (inches) ................... Real
base Pressure (psia)
.............................. Real
base Temperature (deg F)
................... Real
k
Specific Heat Ratio (k)
.......................... Real
u
Viscosity x 10 lbm/ft-sec (mu)
-6
........ Real
PLATE Material
....................
SS=0,Monel=1,CS=2
INPUT hw ............
loop tag.block tag.output
INPUT Pf ..............
loop tag.block tag.output
f
INPUT Tf ..............
loop tag.block tag.output
INPUT Gr .............
loop tag.block tag.output
s
INPUT Zs .............
loop tag.block tag.output
f
INPUT Zf .............
loop tag.block tag.output
INPUT Zb .............
loop tag.block tag.output
N
Exec. Seq. No. ..................... 000 to 250 (000)
Y P
& ).
1 f1
April 2012
(0.0)
(0.0)
(14.73)
(60.0)
(1.30)
(6.90)
(SS)
(null)
(null)
(null)
(null)
(null)
(null)
(null)