SHANGHAI SANZHOU AUTOMATION DASH CO.,LTD

1. Set up the valve, I/P positioner, current source generator, and instrument air supply as shown in the control valve functional test setup file in the end of this article.
2. Check the pressure of the instrument air supply. Make sure it has been according to the I/P Positioner requirements.
3. Apply 4 mA current signal to the I/P positioner. Check the valve stem travel indication, the valve stem shall be in 0% travel. Apply 20 mA current signal to the I/P positioner. Check the valve stem travel indication, the valve stem shall be in 100% travel.
4. If the valve stem travel indication didn’t show correctly 0% or 100% travel, then calibrate the stem travel by using the HART communicator (follow the instruction of the I/P positioner manufacturer). This travel calibration normally will determine the position of 0% and 100% travel + the hysteresis and or linearity correction.
5. Check the five point stem travel (for hysteresis and linearity check) from 0%, 25%, 50%, 75%, 100% and then 100%, 75%, 50%, 25% and 0%.
6. Check the three point stem travel (for deadband check on 5%, 50%, and 95% stem travel).
7. Record the result in the below form for the hysteresis, linearity, and deadband error check.
8. Repeat the step 4 if the hysteresis and or the linearity of the valve travel exceed the acceptance criteria.
9. If the deadband error exceed the acceptance criteria, contact the valve manufacturer for further solution (the valve may require some reparation)

 Hysteresis, Linearity, and Deadband Check Form

Typical tools required:

1. 4-20 mA current source generators
2. HART communicator
3. Instrument air connection
4. Screwdriver set
5. Wrench set
6. Hex key set

This typical functional test procedure is just an illustration of how to regularly test a control valve for academic purpose only. This typical procedure shall not be used as day to day operation guidance. The vendor specific manual shall be used in detail.

Typical Functional Test Setup of Control Valves