Calibration of control valve


#1

Calibration of control valve is to be done as per following steps.

Required Material:

  1. Data sheet
  2. Portable pneumatic calibrator

Step wise Procedure:

 Ask panel man to put the controller in manual mode for control loop

 Isolate the Control valve from the process.

(WARNING – The Isolation of control valve from the process shall be done by field operator. Careful step shall be done to ensure no upset to the operation.)

 Ask panel man to put the controller in manual mode for control loop

 Isolate the Control valve from the process.

 To calibrate a valve first check the input signal range if it is 0.2 to 1.0 Kg/cm2 or different.

 Calculate the span (Difference between higher limit to lower limit=1.0-0.2=.8)

 Now divide it in four equal parts that is 0.2 Kg/cm2 this is 25% of the span.

 Now check the valve travel like 2 inches, 3 inches or any other value.

 Divide it in four equal parts 25% of the travel. That is 0.5 inch for 2 inch valve travel.

 Apply 25% of the span value+ 0.2= 0.4 Kg/cm2 and check is it 25% of travel (0.5 inch) and apply
full span value (1 Kg/cm2) and see you get the complete travel (2 inche).

 Follow the table below for this case.

 If you find difference, adjust the spring accordingly.

 After completion of the job ask panel operator to put loops back in normal mode

 Fill the calibration form and file it for future reference.