The control valve calibration procedure will depend on the positioner you have installed on your control valve. The valve positioner receives data from the controller, then sends pressure to the valve to move it up or down.
The steps of control valve calibration
If you have a pneumatic positioner receiving a signal between 3 and 15 psi, the control valve calibration procedure is entirely manual. Beyond that, the procedure can differ between vendors. For this discussion, we’ll use a Fisher pneumatic positioner and give you an overview of how to calibrate the control valve for it.
First, you need to check the operation cam. Do you have the right cam for your positioner? Did you install it correctly? Then, you need to check the feedback arm. You may need to follow certain steps to install the positioner on the valve, such as keeping the valve in 50 percent of the range when mounting the positioner.
You’ll also need to confirm you have the air supply connected for enough working pressure and the positioner output connected to the valve actuator. Yes, lots of steps before the actual control valve calibration, but you must do them all for your procedure to work.
To begin the control valve calibration, first, you need to supply 4 milliamps (mA) to set the zero position. Then, you’ll supply 20 mA and adjust the span using the flapper.
When you finish the span adjustment, check the zero. You may need to do it again. You’ll go back and forth between zero and span until you have the correct travel. Last but not least, you need to ramp up and down the valve’s travel, using 4, 8, 12, 16 and 20 mA.
That pretty much covers it, the process of control valve calibration. To know more about such products, you can get in touch with our engineers!