Type 2500
Instruction Manual
Form 1013
December 2005
16
Note
Contact your Emerson Process
Management sales office for
information on obtaining the
Supplement to 249 Series Sensors
Instruction Manual: Simulation of
Process Conditions for Calibration of
Level-Trols - Form 5767 (part number
D103066X012).
Wet Calibration
Remove the entire controller/transmitter and sensor
assembly from the vessel. For caged sensors, pour
the fluid into the cage. For cageless sensors,
suspend the displacer to an appropriate depth in a
fluid having a specific gravity equal to that of the
process fluid.
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 Series 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 Type 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 Emerson Process
Management sales office for the
