INSTALLATION
SETUP AND PHYSICAL INSTALLATION
WBPEEUI110504A0
3 - 11
for more information. Figure
includes a graphical representation of this application.
Closed Tank Level Measurements in Condensing Atmospheres
If the atmosphere (vapor state of the liquid) above the liquid is
condensable (such as steam above boiler water), the pressure
line from the upper tap of the tank to the - (low pressure) con-
nection of the cell fills with condensate. This creates a wet leg
or reference leg that exerts a pressure at the low pressure con-
nection of the cell that is greater than that exerted by the vari-
able level on the + (high pressure) connection of the cell.
In Figure
, if h
3
is the level of the liquid at any point
between minimum and maximum level range values, the
transmitter senses the difference in pressure between the fixed
head at h
2
and the variable head at h
3
. As the level of h
3
increases, the difference between h
2
and h
3
decreases. The
transmitter output decreases with increasing level and
decreasing differential pressure. The effect is that of a negative
differential pressure that decreases in numerical value as the
level rises. This negative differential is simulated for calibra-
Figure 3-6. Connecting Piping for Open Tank Level Measurement
N O T E S :
1 . A L L H O R IZ O N TA L L IN E S S H O U L D S L O P E AT L E A S T 8 3 M M /M (1 IN ./F T ) D O W N W A R D T O B L OW D O W N VA LV E S .
2 . T R A N S M IT T E R M U S T B E T H O RO U G H LY V E N T E D TO AVO ID M E A S U R E M E N T E R R O R S .
3 . O P E N TA N K M E A S U R E M E N T : IF R E V E R S E R E A D IN G IS R E Q U IR E D, L O W E R V E S S E L TA P IS C O N N E C T E D T O
L O W S ID E O F T R A N S M IT T E R .
4 . M O U N T T R A N S M IT T E R B E L O W V E S S E L TA P S .
5 . h x S G U R L .
2
≥
1 /4 -IN . T O 1 /2 -IN . VA LV E S .
1 /2 -IN . B L O W D OW N VA LV E S .
1 /2 -IN . P IP E O R 5 /8-IN . O .D. T U B IN G (TO B LO W D O W N VA LV E ).
C O N N E C T IO N IN S ID E O R B OT T O M O F TA N K (F ILT E R SC R E E N S
R E C O M M E N D E D F O R B OT TO M -O F -TA N K C O N N E C T IO N S ).
2 -IN . S U P P O R T P IP E (C U S TO M E R S U P P L IE D ).
T 02 2 20 A
1 /2 -IN . VA LV E S
A
B
C
D
E
B
C
D
+
–
E
A
Содержание Platinum standard Series
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