The control valve receives signals from the DCS that allow it to be opened fully or closed fully only; it cannot be set at positions such as halfway or 75%
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When tuning the pneumatic control valve, it can only be opened to 25%, 50%, and 75% – it won’t open at any other setting. I would appreciate it if experts could advise me on how to adjust it
Could you be more specific with your question? Are you referring to the on-site locator? Send a manual signal at the locator site to see what happens
Measure the input signal to the control valve; if the input signal is correct but the valve does not operate properly, then check the valve
It is this type of control valve: at present, it can only be operated to the fully open or fully closed position; it cannot even be opened to half the signal level
There must be something loose in that locator; there’s no negative feedback
Re-calibrate the locator; with mechanical positioning, it’s necessary to adjust the zero and full positions repeatedly. If possible, switch to an intelligent locator or a semi-mechanical one, as this will significantly reduce the amount of maintenance required