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Instruction Manual
D200124X012
If necessary, you may use water for wet calibration in the shop. You must compensate for the difference between the
specific gravities of water and the process fluid, however. As an example, assume the process fluid has a specific
gravity of 0.7. The specific gravity of water is 1.0. To simulate a process level of 50 percent of the input span, would
require a water level of 35 percent (0.7/1.0 x 50 percent = 35 percent).
Dry Calibration
Remove the controller/transmitter and torque tube arm, as a single unit, from the cage or vessel. Then, wherever the
standard calibration procedures in this manual require a specific process variable input to the sensor, simulate the
process variable by suspending the proper weight (such as a can of sand) from the end of the displacer rod. Complete
the following procedures (Controller/Transmitter and Torque Tube Arm Disassembly) and (Determining the Amount
of Suspended Weight) before proceeding to the Calibrating Procedure.
Controller/Transmitter and Torque Tube Arm Disassembly
WARNING
To avoid personal injury from contact with the process fluid, 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/transmitter and torque tube arm from
the cage or vessel, refer to the appropriate 249 instruction manual for assistance. The method of removing the
displacer or torque tube arm and attached controller/ transmitter varies 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, the sensor may be
removed through the access hole in the sensor head.
For 249BP sensors with travel stop, the stem end piece pins will secure the displacer on the travel stop as long as the travel
stop plate is installed and the sensor head is in position.
Determining the Amount of Suspended Weight
CAUTION
Avoid overloading a torque tube sized for interface or density applications. Consult your
Business Partner for the maximum allowable substitute weight, Ws, that may be used with your particular construction.
2500 and 2503 Controllers/Transmitters
Emerson sales office
June 2017
or Local
21
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