What’s wrong with the control valve?
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Manual mode, moving up and down by oneself – what’s the reason? When set to automatic mode, after it stabilizes for a considerable period of time without any deviation between SV and PV, it experiences frequent zigzag fluctuations
How many control valves are there in the system? It’s possible that the control valve is set to be too sensitive; even minor fluctuations in external pressure cause it to activate
Try making the valve stem longer; when adjusting the valve, it’s essential to have it fully closed, while an opening degree of 80% is not a problem. This phenomenon occurs when the pipeline pressure of such valves equals the cylinder force of the control valve. Try cleaning the locator again.
Liquid or gas? ? Modify the PID parameters.
The PID is set so that the valve moves hardly at all, but it still fluctuates
The mechanical connection of the locator is loose, or there is dust blocking the air passage
This valve has had this problem occur multiple times. After each repair of the instrument, it works for a while before problems arise again
If it is in manual mode, you can ask the instrumentation technician to check whether the locator is functioning properly.
This post was last edited by Honey Home on 2019-2-20 at 12:18. Vertical fluctuations when operating in manual mode may be due to problems with the locator; in automatic mode, fluctuations after it has been running for a while are most likely caused by inappropriate PID parameters. Another possible cause is changes in the conditions of the material over time (such as pressure and temperature).