KROHNE ALTOSONIC V EN - Manual (Page 57)

ALTOSONIC V
Operating Manual rev02 E 7.30850.34.00 Page 57 of 106
5.1.4 Operating with the measured density
For less homogenous products like Crudes it is more practical to measure the density.
The density at 15°C is calculated through iteration by the input of the measured density in a maximum
of 40 steps or a remainder REM less then 10 -5 .
Diagram for calculation VCF from measured density input:
Input for calculating density at 15°C:
•
T
dens
:[°C] Temperature densito meter
• P
dens
:[bar] Pressure densito meter
• ρ dens
:[kg/m3]Density densito meter (measured density)
•
Product type
• Start value for density at 15°C is the mean value of the high and low limits of the required product
type.
In a maximum of 40 loops:
- Calculate the thermal expansion coefficient α
T
with the new found density15
- Calculate the C
tl
factor (C
tl Tdens -->15)
)
- Calculate the C
pl
factor.(C
pl Pdens
)
- Calculate the new density at 15°C by:
pldens tldens
dens
C C ⋅
=
ρ
ρ
15
- Calculate the difference between the newfound density15 and the last found density15. If the
difference is smaller then 0.001% then the newfound density15 is correct, otherwise use the
newfound density15 as new input.
- If the density15 after 40 loops is not found then an alarm is shown on screen and through
Modbus communication.
So the density at 15°C is found.
Practically the conditions (T, P) for the densitometer can differ from the conditions of the measured
flow rate in the UFS-V.
Therefore, the VCF that is eventually used, is calculated using the found density at 15°C as its base
and the conditions of the measured flow rate as its goal.
T
dens
P
de
ρ dens
Product type
Calculate iterative:
density ρ 15
(15°C, 1.01325 bar)
ρ
15
, Product type
T
proces
P
proces
Calculation proces:
ρ
proces
C
tl proces-->15
C
pl proces
Calculation standard:
C
tl standard-->15
VCF
T
standard
C
tl proces-->15
C
pl proces
ρ 15
Product type
T
dens
P
dens
ρ
Densitometer
Product type