VEGA VEGADIF 34 … 51 - Manual (Page 49)

VEGADIF 34 … 51 49
20094-EN-030731
1 Inlet valves
2 Equalization valve
3 Transmitter
4 Vent or drain valves
5 Blow down valves
6 Separator for impurities
7 Block valves
8 Adjustment pot
9 Dosing valve
The differential pressure is determined by the
transmitter as follows:
∆
P
= p
F
+ p
D
– (p
k
+ p
D
)
∆
P
= p
F
– p
k
∆
P
: Differential pressure
p
F
: Hydrostatic pressure of the liquid column
p
D
: Static pressure of the steam
p
k
: Hydrostatic pressure of the condensate column
(constant)
Zero is determined as a negative differential
pressure p
F
– p
k
.
7
6
5
7
6
5
9
2
1
- +
4
3
Installation connections
Installation on closed vessels with overlaid
steam pressure
In a closed vessel with overlaid steam pres-
sure, the sum of the steam pressure and the
hydrostatic pressure acts on the bottom of the
vessel as total pressure. This total pressure is
fed to the plus side of the transmitter. In a
separate vessel a fixed level is generated by
condensate. This condensate column trans-
mits the steam pressure to the minus side of
the transmitter and protects the measuring cell
from hot steam.
The following must be noted:
- The impulse line from the condensate pot to
the vessel must be run with a slight gradient
to the vessel so that excess condensate
returns to the vessel and the level in the
condensate pot remains constant.
- Block valve „7“ between vessel and con-
densate pot must not impede the steam
outlet to the condensate pot; the installation
must prevent water pockets from forming in
the valve.
- If there is insufficient condensate formation
in the condensate pot, additional conden-
sate must be added via dosing valve „9“.
- If the medium has a density other than the
condensate column (1.0 g/cm 3 ), this must
be taken into account for the span adjust-
ment.
For this installation a blow down valve and a
separator for impurities are recommended for
each impulse line. This measure is not neces-
sary if the medium is clean and the formation
of buildup or sludge in the pipelines is not
expected.