Connecting Piping For Open Tank Level Measurement - ABB Platinum standard Series Product Instruction

N O TES :
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 EA S T 8 3 M M /M (1 IN ./FT ) D O W N W A R D TO B L OW D O W N VA LVE S.
2 . TR A N S M ITTE R M U ST BE TH O RO U G H LY V EN T ED TO AVO ID M EA S U R E M E N T E R R O R S.
3 . O PE N TA N K M E A SU R EM E N T: IF R EV E R SE R E AD IN G IS R EQ U IR ED, L O W ER V ES S E L TA P IS C O N N E C TE D TO
L O W S ID E O F TR A N S M ITTE R .
4 . M O U N T TR A N S MIT TE R BE L O W V ES S EL TA P S.
≥
5 . h x S G U R L .
2
E
A 1 /4 -IN . TO 1 /2 -IN . VA LVE S.
B 1 /2 -IN . BL O W D OW N VA LV E S.
1 /2 -IN . PIP E O R 5 /8-IN . O .D. T U BIN G (TO B LO W D O W N VALV E ).
C
C O N N EC T IO N IN S ID E O R B OTTO M O F TAN K (F ILTE R SC R E E N S
D
R E C O M M E N D ED F O R B OT TO M -O F-TA N K C O N N E C TIO N S ).
E 2 -IN . SU P P O R T PIP E (C U S TO M E R S U P PL IE D ).
WBPEEUI110504A0
–
+
Figure 3-6. Connecting Piping for Open Tank Level Measurement
Section 4
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 3-9, if h
between minimum and maximum level range values, the
transmitter senses the difference in pressure between the fixed
head at h
increases, the difference between h
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-
1 /2 -IN . VA LVE S
A
B
and Section 5 for more information. Figure
is the level of the liquid at any point
3
and the variable head at h
2
SETUP AND PHYSICAL INSTALLATION
INSTALLATION
D
C
T 02 2 20 A
3-7
. As the level of h
3
and h decreases. The
2 3
3 - 11
3