How to adjust the PID of the steam control valve?
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The opening of the steam control valve is difficult to adjust. When it is turned on automatically, the process temperature fluctuates greatly up and down the set temperature.
Questions need to be asked in detail. In order to make a good investment in single-loop regulation, each component of the regulation loop must be explained clearly.: Regulating objects, transmitters, regulators, valves, etc. The process is different, and the adjustment is of course different.
Are you talking about using steam to heat chemical raw materials? Because the temperature has hysteresis, a differential link needs to be added.
You must add differential when controlling the temperature. If the fluctuation is large, your ratio is too strong.
First, determine whether the manual state can control the； If the control is stable, it can be ruled out that there is no problem with the output of the controller and the regulating valve. Then the problem may lie in the PID tuning, or it may lie in the field transmitter. I have encountered accidents where the automatic control loop fluctuated due to poor contact at the field transmitter terminals. If it is a PID problem, the following possibilities are possible:: The proportion is too strong, the integration time is too short, and the derivative time is too long. Another possibility is that the temperature measurement instrument is improperly selected or installed in an improper position, causing the temperature measurement lag to be too large, resulting in control imbalance.
The choice of PID system controller is very important. For hysteretic and stable steam temperature regulation, it is recommended to use a PID fixed value controller to control the output value of the regulating valve using a set fixed value, and only occasionally correct the offset. This control method has a good control effect on relatively stable temperatures and temperature change control. Within the set value +-5 degrees, I now have such a control here. It has been running for about a month and the effect is quite obvious. Now I want to add this control to deal with abnormal steam supply and anti-interference ability when the temperature fluctuates violently. Moreover, the adjusted main pipe steam temperature is not consistent with the steam temperature entering the process section. This results in the adjusted temperature not reaching the temperature of the process. Now I plan to use an infrared thermometer to measure the difference between the outer wall temperature of the steam main pipe and the outer wall temperature of the process section, and use this value to correct the set value. I wonder if any friends have any better suggestions.
You can try changing the adjustment plan and changing the adjustment objects