VEGA VEGADIF 34 … 51 - Manual (Page 47)

VEGADIF 34 … 51 47
20094-EN-030731
VEGADIF 44, 45
The transmitter must be mounted on the ves-
sel in such a way that the isolating diaphragm
is completely covered by the medium (even at
min. level).
If the instrument is mounted below the min.
level, the height difference must be taken into
account for the adjustment of zero and span
(the liquid column in the pressure line influ-
ences the meas. result). If the ambient atmos-
phere is extremely dirty, we recommend
applying a filter on the minus side. This pre-
vents the minus side from getting clogged.
Example VEGADIF 44:
Transmitter directly flanged
Example VEGADIF 45:
Transmitter flanged via maintenance unit
1 Transmitter
2 Block valve
3 Emptying valve
h = h
1
– h
2
h = h
1
– h
2
h
1
h
2
∆
p
h = ––––––
ρ
• g
h
1
h
2
∆
p
h = ––––––
ρ
• g
Installation connections
1 Differential pressure transmitter
2 Vent or drain valves
3 Block valve
If in special cases a location above the pres-
sure tapping point is necessary, only the liquid
column above the centre of the measuring cell
is measured.
With such an arrangement, gas pockets can
lead to measurement errors. Impulse line and
measuring cell must therefore be vented regu-
larly.
In both cases the minus side remains open to
the atmosphere. If the ambient atmosphere is
extremely dirty, we recommend for the minus
side a filter or an open vent tube bent down-
wards. This prevents the minus side from
being clogged.
VEGADIF 34, 35
The transmitter should be installed preferably
at the height of the planned pressure tapping
point. If a location below the pressure tapping
point must be used, the height difference „h“
for adjustment of zero and span must be
taken into account (the liquid column in the
impulse line influences the meas. result).