Instruction Manual
D200126X012
2502 Controllers
June 2017
16
Controller and Torque Tube Arm Disassembly
WARNING
To avoid personal injury from contact with the process liquid, lower the vessel level below the sensor torque tube arm, or
shut off the cage equalizing valves and drain the cage before proceeding. For closed vessels, release any pressure that may
be in the vessel before removing the sensor assembly.
When removing the displacer from the displacer rod or removing the controller and torque tube arm from the cage or
vessel, refer to the appropriate sensor instruction manual for assistance. The method of removing the displacer or
torque tube arm and attached controller will vary with the type of sensor.
For a caged sensor with top equalizing connection, it may be appropriate to remove the entire cage from the vessel
before disassembling.
CAUTION
If the displacer is to be disconnected from the displacer rod before the sensor assembly is removed from the cage or vessel,
provide a means of supporting the displacer to prevent it from dropping and suffering damage. The spuds or stem end
pieces on all displacers have holes suitable for inserting rods or other supports.
Additionally, a threaded rod may be installed into the 1/4‐inch 28 UNF threaded hole in the displacer spud or stem end piece
of top‐mounted cageless and all caged sensors. For some top‐mounted sensors with long displacers, it may also be possible
to remove the sensor through the access hole in the sensor head.
For the 249BP sensor with the 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.
Determining Suspended Weight for Calibration
CAUTION
or Local Business Partner for the maximum allowable substitute weight W
s
that can be used with your
particular construction.
To determine the total weight that must be suspended from the displacer rod to simulate a certain condition of liquid
level or specific gravity, solve the following equation:
W
s
= W
d
‐ [(0.0361) (V) (SP GR)]
where:
W
s
= Total suspended weight in pounds (should never be less than 0.5 pounds). For a unit with a horizontal
displacer, make sure the center of gravity of the substitute weight is where it would be on the actual displacer.
Note
For liquid level control only, simulate the lower range limit of the input span by suspending the displacer from the displacer rod.
For other values of input span, remove the displacer and suspend the appropriate weight as determined in the equation above.
