Control valve

The poster asked whether the control valve is an analog control valve with PID output control or a on/off valve. If it is a control valve driven by PID output, it cannot be set to automatic mode; overshoot occurs. This is not a problem with the valve itself, but rather an issue with the improperly set PID parameters. It is necessary to reset the PID parameter values of the regulator, and it should be noted that adjustments need to be made several times based on the actual operating conditions. The PID parameter values cannot be chosen arbitrarily – the quality of regulation depends on these values.

It is a control valve with PID control; when in manual mode, the flow rate still fluctuates but can be stabilized. Once switched to automatic mode, however, the fluctuations become uncontrollable. I hope the person above can provide a more detailed and specific solution

Could it also be a problem with the locator? Because similar problems have occurred in our factory.

First, determine whether the valve will over-adjust when operated manually, whether it is in a fully closed or fully open position, and whether it has been calibrated before being put into use. The locator has a PID adjustment function; it is possible to reduce the proportional value slightly and increase the integral value. Additionally, the speed at which the valve operates can be adjusted, as well as the dead zone size

If stabilization is achieved manually, it rules out problems with the controller. If fluctuations remain severe, first eliminate the differential action (the function of differential control is to make adjustments based on the speed of deviation; the higher the frequency of deviation, the greater the output, which increases the likelihood of oscillations). If fluctuations are still present, it indicates that the proportional or integral action is too strong. First reduce the proportional action, and once the fluctuations decrease, then reduce the integral action. By adjusting these parameter values several times, the quality of control can be significantly improved. My personal understanding, for reference only...

The locator itself is a PID control module; check whether the PID parameters in the DCS are set properly. If not, have the locator perform self-tuning, or modify the PID parameters in the locator manually if necessary

Is yours an intelligent locator? Intelligent models can auto-tune PID parameters, and if it has the HART protocol, a handheld device can be used to monitor the locator’s status.

If it can be stabilized manually but experiences large fluctuations when set to automatic mode, then there’s definitely an issue with the PID parameter settings. The solution was explained in great detail upstairs; just follow his methods

Adjusting PID parameters is not something that can be done quickly; even using the method mentioned above, it may not be possible to get the settings right in a short time. This depends on the trend curve of your measurement values; adjustments should be made based on the patterns in those measurements. At the same time, it is necessary to assess any interference issues related to the process; you need to make this judgment on your own, as no one else can help you. During the adjustment process, it is important to ensure that the feed rate and operations remain stable, and to eliminate any interfering factors; only in this way can the curve accurately reflect issues related to inappropriate PID parameters. If there are process disruptions, it becomes very difficult to make adjustments. In short, it takes time to figure things out; there’s no rush. It’s a slow process.