RMG ERZ2000-NG, Operating Manual

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6 Flow meters
Manual ERZ 2000-NG · EN07 · 2019, May 13th
199
Error equation:
2
2 1 0 1
2
2 Re
Re Re
Re
1
Re
1
˜ ˜ ˜ ˜
A A A A A F
Reynolds number equation:
K T
T
p
p
DN
Q
n
n
n
b
1
353677 , 0 Re
˜ ˜ ˜ š ˜ ˜
U U
K
U
Where
F
Re
= error curve deviation [%]
Re
= Reynolds number
A
n
= constants
K = Viscosity
(Menu AM Viscosity ,
K
as a constant for natural gas
K
= 12 * 10
-6
m
2
)
The polynomial coefficients
A
n
(
n
= -2, -1, 0, 1, 2) are calculated from the measured
value pair error
F
Re
,i
and Reynolds number Re
i
.
Instead of the constant meter factor
K
V
, the corrected meter factor
K
VK
is used for
further calculation and/or conversion.
ܭ
௏௄
ൌ ܭ
௏
ڄ ൬ͳ ൅
ܨ
ͳͲͲ
൰
The polynomial coefficients
A
n
are delivered by the manufacturer of the flow rate
measuring device (turbine meter, ultrasonic meter, etc.).
Characteristic curve correction with Straatsma polynomial
This correction functions in a similar manner to the process with flow-rate-related pol-
ynomial. However, the Straatsma polynomial correction also includes Q
Vb, max
of the
meter that is used. In addition, special Straatsma coefficients are used. The polyno-
mial coefficients
A
n
from the manufacturer of the flow rate measuring device (turbine
meter, ultrasonic meter, etc.) are also delivered here.
A polynomial function which ideally reflects the curve running through these points is
calculated from the polynomial coefficients provided by the manufacturer. The coeffi-
cients of the polynomial that the manufacturer has provided must be entered subor-
dinately in Table
GE33 to GE37 (and GE38 to GE41 for the Straatsma correction).
The same function is also provided for reverse operation under
GF Error curve linearization, reverse flow . Since the structure is identical, no addi-
tional explanation is provided.