How-to do Control Valve
Calibration?
Control Valves are meant to control the process parameters namely
Pressure, Flow, Level and Temperature.
Control Valve is the final control element in any closed-loop control.
Based on their application type they are named as Pressure Control
Valve, Level Control Valve, and Temperature Control Valve.
Calibration is the quantitative determination of errors of a measuring
device and, where necessary, adjusting these errors to a minimum. The
error is comparison with higher standard having traceability to
National or International standard.
Control Valve Calibration
Following the receipt of the Work Request which is generated through
SAP, the instrument engineer will submit Safety Document Request
(Generated by SAP) one day in advance for the work planned. Some
Industries will use manual work permit systems in the absence of SAP.
Confirm isolation before receiving the safety document.
Check the interlock in the relevant logic diagram for the valve to be
stroked. Simulate or force the necessary signal like valve position etc
to ensure safe operation of the process before starting the job.
Check the healthiness of I/P Converter, Position feedback
transmitter, airlock relay, solenoid valve, and air supply pressure.
Check the manual operation of the valve using the hand wheel. Stroke
the valve either from local or from DCS as applicable. Confirm the
valve travel from local. Calibrate the Valve with the inbuilt option like
“Auto Calibration” available in the valve positioner. Also, check the
Limit switches function and adjust them as required.
For the SMART Control Valve, we can use a HART communicator to
calibrate the control valve. Give the supply pressure according to the
valve as per nameplate details. Connect the HART to the valve
positioner. Then go to valve simulate command, enter 0% and observe
the valve position. Next, enter 25% in HART and observe the valve
travel position.
Similarly, enter 50%, 75% and 100% in the HART communicator then
observe the valve stem travel position accordingly. You can find a
manual scale (0% to 100%) with a needle on the valve to verify the
valve travel position.
Confirm the signal status and remove all the simulation/forces, which
were done before starting the job.
Clear and return the work Permit to the Plant Shift Manager. Update
the Work Order in SAP.
Share your experience with us on the Calibration of Control Valves, use
the comments section.