any body can explain that an oprater tell you that a control valve is in hunting condition what action you will change in controler proportional integral or derivative?
1) Positioners use feedback control to do the task of positioning the valve stem to match the control signal.
Hunting can be caused by either positioner mistuning or loop controller tuning constants that are too aggressive, as Pritam points out.
If the valve in question has a positioner, a hunting problem could positioner tuning, or loop tuning.
2) Loose linkage can cause hunting.
3) In answer to your question about loop tuning constants, here's a direct quote from Spirax Sarco's site (near the bottom of the web page) from a Google search for 'control valve hunting':
Hunting
Often referred to as instability, cycling or oscillation. Hunting produces a continuously changing deviation from the normal operating point. This can be caused by:
Hunting
The proportional band being too narrow.
The integral time being too short.
The derivative time being too long.
A combination of these.
Long time constants or dead times in the control system or the process itself.
Any and/or all of them, for the loop is clearly not tuned for stability.
There are proven techniques for tuning a loop, and the controller terms selectable depend whether fastest response is requred, zero overshoot, or somewhere in between.
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Hunting Condition
Re: Hunting Condition
