Fisher FIELDVUE DLC3010 Quick Start Manual page 27

Quick Start Guide
D103214X012
1. Determine all the information you can about the 249 hardware: 249 type, mounting sense (controller to the right or
left of displacer), torque tube material and wall thickness, displacer volume, weight, length, and driver rod length.
(the driver rod length is not the suspension rod length, but the horizontal distance between the centerline of the
displacer and the centerline of the torque tube). Also obtain process information: fluid densities, process
temperature, and pressure. (The pressure is used as a reminder to consider the density of an upper vapor phase,
which can become significant at higher pressures.)
2. Run Instrument Setup and enter the various data that is requested as accurately as possible. Set the Range Values
(LRV, URV) to the PV values where you will want to see 4 mA and 20 mA output, respectively. These might be 0 and
14 inches on a 14 inch displacer.
3. Mount and couple at the current process condition. Do not run the Capture Zero procedure, because it will not be
accurate.
4. With the torque tube type and material information, find a theoretical value for the composite or effective
torque-tube rate, (refer to the
Transmitters supplement
The value can be accessed by selecting:
Configure > Manual Setup > Sensor > Torque Tube > Change Torque Rate (2-2-1-3-2).
If you select the 'Need Assistance' option instead of the 'Edit value directly' approach, the procedure can look up
values for commonly available torque tubes.
5. If the process temperature departs significantly from room temperature, use a correction factor interpolated from
tables of theoretical normalized modulus of rigidity. Multiply the theoretical rate by the correction factor before
entering the data. You should now have the gain correct to within perhaps 10%, at least for the standard wall, short
length torque tubes. (For the longer torque tubes [249K, L, N] with thin‐wall and a heat insulator extension, the
theoretical values are much less accurate, as the mechanical path departs considerably from the linear theory.)
Note
Tables containing information on temperature effects on torque tubes can be found in the Simulation of Process Conditions for
Calibration of Fisher Level Controllers and Transmitters instruction manual supplement (D103066X012), available from your
Emerson Process Management sales office
some host applications with graphical user interfaces.
6. Using a sight glass or sampling ports, obtain an estimate of the current process condition. Run the Trim Zero
calibration and report the value of the actual process in the PV engineering units.
7. You should now be able to go to automatic control. If observations over time show the instrument output exhibits,
for example,1.2 times as much excursion as the sight glass input, you could divide the stored torque tube rate by
1.2 and send the new value to the instrument. Then run another Trim Zero calibration and observe results for
another extended period to see if further iteration is required.
Simulation of Process Conditions for Calibration of Fisher Level Controllers and
for information on theoretic torque tube rates), and enter it in the instrument memory.
or at www.fisher.com. This document is also available in the device help files linked to
DLC3010 Digital Level Controller
February 2016
27