Rotary Ball Valve

hello everyone. I have one question regarding 10 inch ball valve which controlling steam header line with 5 bar start malfunctioning and hunting during the valve in AUTO mode but in manually valve smooth as well as the flow element.

seeking your advise.

regards.
 
Since you say it 'start'-ed malfunctioning, and the valve can control to a steady state in manual mode, then something in the process has changed.

Either find out what's changed and change it back or re-tune the process controller that drives the valve position to take into account the new process conditions.

Neither I nor anyone else on the forum can tell you what's changed, because we're not there.
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Since you say it 'start'-ed malfunctioning, and the valve can control to a steady state in manual mode, then something in the process has changed.

Either find out what's changed and change it back or re-tune the process controller that drives the valve position to take into account the new process conditions.

Neither I nor anyone else on the forum can tell you what's changed, because we're not there.
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dear David, thanks for your clarification. however, the line pressure is stable only flow and valve Fluctuating please advise.
 
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