CALIBRATION OF DISPLACER TYPE LT FISCHER DLC 3010
A Level troll in and instrument used for measuring the liquid level between two known points. The Level troll works on the buoyancy principal. Leveltrol has a float, which submerses proportionately with liquid level raise in the float chamber. The amount of submersion of the dis placer depends on the liquid density, which produces a torque. The amount of torque produced in measured in terms of % of level.
Parts of Level troll:
Float chamber, Float, Torque lever, Knife edge, Feedback Bellows, Air Relay, Restriction, Flapper, Nozzle, Feedback link, Density range, Action change lever, HP and LP flange,
Get Override from panel engineer and get PTW to work on the LT
Isolate the process from LT, i.e. isolate the three isolation point water, oil and gas points respectively and connect Hart communicator to the LT
Vent the gas from the upper bleed ring of the LT and drain the process from the chamber of level transmitter
Initial set up
Communicator Configure > Calibration > Primary > Guided Calibration (2-5-1-1) then enter the following values
Display length unit > cm
Displacer weight> 3.200 kg
Displacer volume> 2686.1 mL
Displacer length> 290cm (not 380cm-default value- because here URV is 290)
Driver rod length> 20.00cm
Instrument mounting>left of displacer
Level offset>0 cm
Desire action > Direct
Engineering unit of PV >cm
If you only have a single fluid for calibration like water, run through Instrument Setup and verify all displacer data is correct. Set
Level Offset to 0. Select mode to Level application with direct action, and enter SG=1.0 (water) or actual SG of test fluid if different than 1.0. Proceed with Min/Max calibration; note that now the mode is in “LEVEL”.
The following procedure can be used to calibrate the sensor if the process condition can be changed to the equivalent of a completely dry and completely submerged displacer, and sight glass is available
Correct displacer information and the SG of the test fluid must be entered before performing this procedure.
Follow the prompts on the Field Communicator to calibrate the instrument and sensor.
Set the control loop for manual control.
Enter the specific gravity for the liquid in the system here water
s.g. = 1.00
Follow hart instructions Configure>Calibration>Primary>Full calibration>Min/Max calibration
Hart communicator will ask you whether the displacer is dry. Adjust the water level until the displacer is dry, that is, no water condition. Allow the output to settle, then acknowledge establishment of the minimum buoyancy condition to the system, accept this as the ‘Min’ condition. then enter min in hart communicator
Hart communicator will then ask you to establish fully submerge the displacer with test fluid. Adjust the water level until the displacer is completely submerged in the liquid up to 290 cm. Allow the output to settle, then acknowledge establishment of the maximum buoyancy condition of the system Accept this as the ‘Max’ condition and then enter max in hart communicator.
The sensor torque rate is calibrated now, after this follow the step below to change to interface measurement
Run through Guided Setup and verify that all sensor data is correct.
Change the PV mode to “Interface”.
Set the Level Offset value to 0.00
Set the Specific Gravity of lower liquid to 1.09 and upper to .85 and continue to calibration check (not calibration here)
Since we are using interface measurement, we need to change the measurement mode to interface and check whether the calibration done is correct or not. Here it should be noted that this is cross checking for interface measurement and not the calibration as in min/max capturing
Mark in the chamber first point from zero level as 2900mm ie 100% (2900*1.00 i.e. s.g. of lower liquid here water 1.00)
Mark the second point as 2465m as 0% (2900*0.85 i.e. s.g. of upper liquid here crude 0.85) and we will perform calibration check between this 0 to 100 % range
Fill the chamber with water up to 2900 *1.00 =2900 mm and check for 100% interface level measurement, the transmitter should show 100% and 20 mA
Fill the chamber with water up to 2900 *0.85 =2465 mm and check for 100% interface level measurement, the transmitter should show 0% and 4 mA
Once the calibration and calibration check is over, put the vent plug and drain plug and isolate both vent and drain valve and open the gas isolation valve, followed by the oil isolation valve and then finally the water isolation valve and now the LT is taken into line and the reading now showing is the interface level measurement.
Allow the process for settle for half an hour and observe the LT reading
N.B.: here it should be noted that the If the digital level controller is not already coupled to the sensor, then it cannot be calibrated, so perform the following procedure to couple the digital level controller to the sensor.
Slide the access handle to the locked position to expose the access hole. Press on the back of the handle as shown in
Then slide the handle toward the front of the unit. Be sure the locking handle drops into the detent.
Last but not the least, there are nearly 7 procedures to calibrate a displacer type transmitter