Oscillation of control valve
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The equipment is equipped with a pneumatic control valve and a disc valve; the supply of instrument air is stable, and full opening and full closing work properly. However, once a fixed opening degree is set, the control valve oscillates back and forth at that degree from time to time. The set signal remains stable – how can this be adjusted?
Are there any other accessories outside the locator? If not, it’s a problem with the locator.
Will the control valve oscillate back and forth at a certain opening degree? Is it the change in the opening value displayed on the locator, or is it a change in the valve’s position?
When the pressure gauge of the pressure relief valve is stable, it is recommended to perform self-tuning on the regulator. If it is a mechanical type or self-tuning does not work, check whether the shaft of the feedback linkage is stuck
It is also possible that the instrument air contains moisture, or there is water droplets or scale on the rubber diaphragm of the amplifier or at the nozzle
This post was last edited by Sunflower001 on 2017-1-4 23:56. 1. Is the operating condition stable? 2. Check the valve data sheet to determine whether the selection is appropriate. 3. What brand is the locator made of? Can self-tuning eliminate the issue? Are there any other accessories? Is the exhaust port blocked? 4. Is there an excessive gap in the rotating parts of the valve? 5. Is the instrument air clean? 6. Check if the feedback is loose. 7. Are there any impurities inside the valve, and is the packing too tight, causing the valve to stick? 8. Whether the PID is appropriate under automatic process operation. 9. Are there any signal interferences or pipe vibrations, and is there a mixture of gas and liquid in the medium? 10. Under automatic control, do the corresponding temperature, liquid level, and pressure experience fluctuations on their own, thereby causing the valve to operate? Too much talking only leads to tears; after closing the inlet and outlet valves, adjust the positioner first, and finally determine whether the process always operates at a low flow rate.