Range Calibration
Through ValVue, the SVI position sensor can be calibrated either automatically or manually using the
Auto Stop Limits or Manual Stop Limits method. The supply pressure must be at least 5 psi above the
upper spring range of the valve so that mechanical stops can be reached by exhausting and filling the
valve actuator.
•
Auto Stop Limits:
Clicking the Auto Stop Limits button initiates the automatic position
calibration process in the SVI. The actuator is fully exhausted and then fully filled, and the
position signal corresponding to each position stop is measured and saved. For some cases
like extremely large size actuators, this procedure may fail due to time out. Manual Stop
Limits method should be applied if Auto Stop Limits fails. After position calibration, check if
the calibration is done properly by clicking the Full Open and Full Closed button and valve
positions at stops are displayed correctly.
•
Manual Stop Limits:
Clicking the Manual Stop Limits button initiates the manual position
calibration process in the SVI. The valve is moved to one mechanical stop and waits for
user's confirmation, and then is moved to another mechanical stop and waits for user's
confirmation.
•
Open Stop Adjustment:
For some valves the open position stop exceeds the nominal travel
of the valve. By entering a value in the Open Stop Adjustment, and clicking the Auto Stop
Limits or Manual Stop Limits button to run the calibration, the valve position can be adjusted
to nominal travel. For a valve with fully close and open corresponding to its mechanical stop,
the value is simply 100. Otherwise, you may use the following procedure to determine the
value:
1.
Enter 100 in Open Stop Adjustment and choose either Auto Stop Limits or Manual Stop Limits to
complete initial position calibration. This will calibrate the valve position as 100% at the open
mechanical stop.
2.
Click OK to return to manual mode.
3.
Manually adjust the valve position (using the scroll bar or the set position button) until the valve is
at the full open nominal position. Make note of the valve position reading, for example, 80%.
4.
Return back to this Range page.
5.
Enter the position reading, e.g., 80 in the Open Stop Adjustment edit box and repeat the position
calibration procedure again.
The valve will now be calibrated for nominal travel. If position calibration is run subsequently, do not
enter any value in the Open Stop Adjustment - the SVI will remember the proper value to use.
53
Range calibration moves the valve over its entire
stroke. Isolate the valve from the process prior to
calibration.
WARNING
Note:
Valve supply pressure must be at least 5 psi higher than the upper spring range of the
valve.
