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supporting the displacer to prevent it
from dropping into the vessel and suf-
fering damage.
To help support a Type 249BP or 249CP displacer,
install the displacer stem and stem end piece, or a
threaded rod, into the 1/4 inch-28 UNF threaded hole
in the displacer spud or stem end piece (figure 8). On
the Type 249BP with optional travel stop, the stem
end piece pins will secure the displacer as long as the
travel stop plate is installed and the sensor head is in
position.
Side-Mounted Sensor
If a stillwell is required (figure 7), the displacer must be
attached to the displacer rod from inside the vessel.
Connect the displacer as shown in figure 8, locking the
assembly with the cotter spring provided. If a stillwell
is not required, the displacer can be attached to the
displacer rod before mounting the sensor to the vessel
connection. The displacer may then be swung out hor-
izontally for insertion into the vessel. If an extension is
used between the displacer spud and the displacer
stem end piece, make sure the nuts are tight at each
end of the displacer stem extension. Install and tighten
suitable bolting or cap screws in the flanged connec-
tion to complete the installation.
Top-Mounted Sensor
Figure 7 shows the installation of a top-mounted cage-
less sensor. The displacer may be attached to the dis-
placer rod before installing the sensor on the vessel.
Where the displacer diameter is small enough, it may
be desirable to install a long or sectionalized displacer
through the sensor head access hole after the sensor
is installed on the vessel. Connect the displacer as
shown in figure 8, locking the assembly with the cotter
springs provided. If a stem is used between the dis-
placer as shown in figure 8, lock the assembly with the
cotter springs provided. If a stem is used between the
displacer spud and the stem end piece, make sure the
nuts are tight at each end of the stem. Install and tight-
en suitable cap screws in the flanged connection to
complete the installation.
Special Constructions
Temperature-Compensated Displacer
Some sensors use a temperature-compensated dis-
placer (figure 9). This displacer is appropriate for den-
sity applications that do not tolerate specific gravity
changes due to temperature. The displacer must be
filled with the liquid to be measured, or with a liquid of
equal expansion coefficient. In service, the displacer
DISPLACER
STEM
END PIECE
DISPLACER
STEM
EXTENSION
W0229-1A/IL
DISPLACER
SPUD
W0228-1A/IL
Figure 8. Displacer/Displacer Rod Connections
A0746–1/IL
Figure 9. Temperature-Compensated Displacer
2502 Series
DISPLACER ROD
COTTER SPRING
LOCKING NUTS
DISPLACER SPUD
COTTER SPRING
DISPLACER ROD
7
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