KROHNE Summit 8800 Vol 2 - Manual (Page 179)

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08/2013 - MA SUMMIT 8800 Vol2 R02 en
SUMMIT 8800 APPENDIX 2: LIQUID CALCULATIONS 16
16. Appendix 2: Liquid calculations
16 .1 Perform meter curve linearisation
For liquid meter correction an individual meter factor or K-factor curve of points can be entered.
Up to 20 flow rates with a corresponding K-factor can be entered.
The correction of K-factor and/or frequency may be entered via the keypad under access control.
A separate trigger point is provided to put all the new entered values into use at the same mo-
ment, which avoids any problems with temporary inconsistent data.
The flow computer searches the table to find an index ‘I’ so that fi < f < fi+1. If it succeeds in find-
ing a suitable pair of points before reaching the end of the table, the exact K-factor is calculated
by linear interpolation:






−
−
− + =
+
+
i i
i
i f i f i f lin f
f f
f f
K K K K
1
, 1 , , ,
* ) (
Equation 6 Liquid K-factor calculation
f Measured frequency [Hz]
fi Nearest stored frequency in meter curve below f [Hz]
fi+1 Nearest stored frequency in meter curve above f [Hz]
Kf, i Stored K-factor at fi [pulse/m³]
Kf, i+1 Stored K-factor at fi+1 [pulse/m³]
Kf, lin Interpolated K-factor [pulse/m³]
If no pair of points can be found that bracket the actual frequency, the single frequency point
closest to the measured value is selected. The corresponding K-factor is then applied without
adjustment.
16 .2 Linear corrected volume flow [m3/h]
The flow computer calculates actual volume flow rate as:
3600 * *
,
M F
K
f
q
lin f
line
=
Equation 7 Actual volume flow rate
qline Gross volume flow rate [m³/h]
f Frequency [Hz]
Kf, lin Linearised K-factor [pls/m³]
MF Meter factor from proving [-]
The linearised K-factor is based on K-factor corrected with the meter curve linearisation
The meter factor is determined from proving. When the proving is completed the controller will
calculate an average value for the new meter factor to be used by the duty meter. This meter
factor has to be manually entered in both flow computers.