Calibration of the control valve can be done in many ways as there are different type of control valve used in industries.
If the control valve has SMART positioner then to calibrate it you have to follow some step and use a push button to calibrate it like Samson or siemens SMART positions.
Some of the control valve positioners come with span and zero adjustments, especially in pneumatic type.
Some control valve has a D-shaped mechanical type positioner in which you have to adjust zero and span to adjust flapper-nozzle assembly.
In this article, I will cover the calibration of the control valve.
3. control valve
4. Air supply
Do the connection as shown in the below figure.
Follow the below step for the calibration: (Emerson 475)
1. Tell the operator to put the loop in manual mode.
2. Remove a valve from the process. (Tell field operator to remove the valve with precaution without any upset in the operation. Must follow safety step.)
3. Connect HART in the loop (+,-) and verify tag number, etc parameter.
4. Using HART click on "configure" option. Here, you will find "manual-calibration" and "auto-calibration". select the mode of calibration.
5. Here, I have select "auto-calibration", now select "out of service" option to remove it from the loop.
6. Due to our selection of "auto-calibration" process will start automatically. It will show seeking High drive it means that the valve is heading toward 100%.
7. It will adjust automatically at 75%, 50%, 25% points.
8. You will get a message of travel calibration successful and once again in the last step, it will check travel as per set target.
9. Put back loop into service again.
10. Install valve again in-process and tell operator to put in the auto mode again.
(NOTE: HERE, TO FOLLOW ABOVE STEP YOU DOESN'T NEED TO REMOVE VALVE FROM THE PROCESS. BUT IF THERE IS ANY PROBLEM WITH TRAVELLING MEANS IT'S NOT OPENING FULLY OPEN OR FULLY CLOSED YOU HAVE TO SET BENCH SET RANGE FOR THAT YOU HAVE TO DISLOCATE VALVE AND YOU NEED HAVE TO REMOVE IT FROM PROCESS.
BUT FOR SAKE OF THE SAFETY ITS BETTER TO REMOVE VALVE FROM THE PROCESS AND DO CALIBRATION IF THERE IS NO URGENCY.)