KROHNE Summit 8800 Vol 2 - Manual (Page 184)

184 www.krohne.com 08/2013 - MA SUMMIT 8800 Vol2 R02 en
SUMMIT 8800 APPENDIX 2: GAS CALCULATIONS 17
17. Appendix 3: Gas calculations
17 .1 Perform meter body correction
If the operating temperature and pressure is different from the conditions at high pressure cali-
bration, the cross sectional area of the flow meter will change slightly. The following correction
can be applied to the raw flow rate to compensate for this. The basic configuration has no meter
body correction applied.
Meter body correction calculations
The system corrects the volume flow for the impact of pressure and temperature on the geom-
etry of the flanged meter body according to ISO standard 17089-1.
Simplified direct single-stage calculation is used which estimates the effect for pressure and
temperature:
1) Body temperature effect
( )
T =
Q
Q
ature bodytemper
∆ +






* * 3 1
0
1
α
Equation 21 Meter body temperature effect
Where:
Q1/Q0 Flow correction factor for the meter output [-]
α Thermal expansion coefficient [K-1]
ΔT Temperature difference [K]
With:
cal op
T T = T
− ∆
Equation 22 Delta meter body temperature
Where:
Top Field operation temperature [K]
Tcal Calibration temperature [K]
2) Body pressure expansion





 ∆






+
−
+
+






E
P
R a
R a
=
Q
Q
re bodypressu
* * 4 1
2 2
2 2
max 0
1
σ
Equation 23 Meter body expansion
Where:
Q1/Q0 Correction factor for the meter output [-]
R Inside pipe radius [m]
α Outside diameter of the meter body [m]
σ Poison’s ratio [-]
ΔP Pressure difference [Pa]
E Modulus of elasticity [Pa]