VEGA VEGADIF 65 Foundation Fieldbus - Manual (Page 27)

27
4 Mounting
VEGADIF 65 • Foundation Fieldbus
36130-EN-130417
+
–
min.
max.
1
2
3
4
5
+
–
Fig. 26: Measurement setup in closed vessel with superimposed steam
1 Condensate vessel
2 Blocking valve
3 Separator
4 Drain valve
5 VEGADIF 65
4.6 Measurement setup density and interface
In a vessel with varying level and homogeneous density distribution,
density measurement with a differential pressure transmitter can be
realized. The connection to the vessel is made via a chemical seal on
two measuring points. To reach a high accuracy, the distance between
these points must be as big as possible. The density measurement is
only ensured with a level above the upper measuring point. If the level
drops below the upper measuring point, the density measurement is
interrupted.
This density measurement functions with open but also with closed
vessels. Make sure that small density changes cause only small
changes to the measured differential pressure. Select a suitable
measuring range.
The density measurement is carried out in the mode level measure-
ment.
1. Mount VEGADIF 65 below the lower chemical seal
2. The ambient temperature should be the same for both capillaries
Example for a density measurement:
Distance between the two measurement points: 0.3 m
Min. density: 1000 kg/m³
Max. density: 1200 kg/m³
Measured differential pressure: Δp = ρ • g • h
The min. adjustment is carried out for the differential pressure meas-
ured at density 1.0:
Δp = ρ • g • h
= 1000 kg/m³ • 9.81 m/s
2 • 0,3 m
= 2943 Pa = 29.43 mbar
Density measurement