19
TN4FCXA2
j
-EDF-
E
%
0
20
40
60
80
100
%
0
20
40
60
80
100
H
1
H
2
ρ
0
ρ
h
1
ρ
%
0
20
40
60
80
100
H
1
ρ
h
ρ
1
(1) When connecting the valves or of manifold, take appropriate protective
measures to avoid the ingress of foreign bodies in the atmospheric release
vents.
(
2) When measuring low pressures, it is important to take into consideration
the following points and to limit the effects as much as possible:
• Atmospheric pressure variation due to the wind around the transmitter
• Variation of the ambient temperature in the vicinity of the pressure
take-off pipe.
• Air pressure difference between the pressure take-off pipe and the
location of the transmitter.
To prevent the phenomena cited above, the side atmospheric pressure
connection must be fitted with a pressure damper (adjustable to low flow), with
the transmitter possibly mounted in a protection housing, or a compensation
pipe installed on the low pressure side.
High level
Low level
Venting into
atmosphere
5- Measurement of gas pressure
The transmitter must be installed above the pipe to
avoid condensation in the connecting pipes and in
the measurement chambers of the transmitter.
6- Level measurement
(1) Reference column full
The reference column (on take-off pipe at the
top point) must be full of liquid and connected
on the low pressure side of the transmitter. The
take-off pipe at the low point must be connected
on the high pressure side of the transmitter.
Formula for calculating the level:
Zero:
ρ
.H2 -
ρ
o.H1
Scale (∆P):
ρ
H
2
+
ρ
1
h –
ρ
0
H
1
ρ
o,
ρ, ρ
1: density
H2: low level
H1: high level
h: variation in level
(2) Reference column empty
For an open tank, the low pressure side of the
transmitter must be vented.
Formula for calculating the level:
Zero:
ρ
.H1
Scale (∆P):
ρ
.H1 +
ρ
1.h
ρ, ρ
1: density
Condensate
vessel
High level
Low level
Pressure reading
connector
Piping
mechanism
Manifold
Connection piping
Isolating valve
Venting into
atmosphere
Manifold
Manifold
ATTENTION
