Introduction
A pneumatic valve positioner is an essential automation component. It precisely controls actuator movement so the valve can regulate accurately during production. Positioner adjustment directly determines the control accuracy of the complete pneumatic valve system. This article organizes commissioning into 6 steps for engineering personnel.
1. Equipment preparation and inspection
Before commissioning, confirm correct installation and connections:
- Check that the positioner is correctly fitted to the actuator, with secure connections and no looseness.
- Check air and control-signal circuit connections for leaks or wiring errors.
- Verify that supply pressure meets the positioner's technical requirements, usually 3–5 bar.
2. Air and electrical power
Once all connections are confirmed, turn on the air supply and power the system:
- Stable air supply: maintain steady pressure without fluctuations.
- Correct power supply: confirm normal power input and that the positioner's power indicator is illuminated.
3. Calibrate zero and span—the key step
Zero and span calibration is the core of commissioning. It ensures accurate valve travel throughout the control-signal range:
Zero calibration
- Set the input signal to its minimum, usually 4mA or 0%.
- The positioner should move the valve to fully closed.
- If it is not fully closed, manually adjust the zero adjustment screw until complete closure is achieved.
Span calibration
- Set the input signal to its maximum, usually 20mA or 100%.
- The positioner should move the valve to fully open.
- If full opening is not reached, adjust the span adjustment screw.
4. Signal adjustment and travel testing
After initial calibration, change the signal gradually and observe the valve:
- Signal adjustment: Gradually increase from minimum to maximum, for example 0–100%, and check for smooth movement throughout the range.
- Travel test: Increase and decrease the signal step by step to test fully open and fully closed travel, ensuring an accurate response to every input.
5. Feedback checks and accuracy verification
For a positioner with feedback, also check feedback accuracy:
- Feedback signal check: Measure the output with a multimeter or signal tester, ensuring it corresponds to actual valve position.
- Accuracy adjustment: If the signal does not match the position, adjust the internal feedback mechanism or recalibrate.
6. Fault protection and final checks
After commissioning, make a comprehensive check to verify operation under all conditions:
- Fault alarm: Confirm that alarms are enabled and operate correctly on air supply failure or signal loss.
- Travel limit protection: Check that travel remains within the preset minimum and maximum limits.
- Operational verification: Repeat tests under actual operating conditions, confirming smooth movement without sticking throughout the stroke.
7. Calibration quick-reference table
| Item | Signal value | Target position | Adjustment method |
|---|---|---|---|
| Zero | 4mA / 0% | Fully closed | Zero adjustment screw |
| Span | 20mA / 100% | Fully open | Span adjustment screw |
| Air supply pressure | 3–5 bar | Stable air supply | Pressure regulator |
Conclusion
A standardized commissioning procedure substantially improves positioner accuracy and efficiency, ensuring reliable industrial operation. Remember the four core actions: check connections → calibrate zero and span → test travel → verify feedback. Contact our professional service team for positioner selection and commissioning support.
Zhejiang HES Automatic Instrument & Valve Co., Ltd. Established in 1989 · More than three decades dedicated to pneumatic actuators and pneumatically operated valves. Website: www.hesvalve.com