Valve opening adjustment: How are automatic and manual implemented?
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Please tell me, there are two ways to adjust the general regulating valve: automatic and manual. When manual, you can directly input the percentage opening for manual adjustment. Automatic regulating valves generally control their opening and closing or at a certain opening through P and T. Even for automatically adjusted valves, the configuration software provides the function of "switching to manual mode" when necessary, and general configuration requirements require this function. So please tell me: The so-called manual state can directly input the percentage opening to manually adjust/manually adjust the valve opening. How are these two methods achieved? Who can explain in detail how to input the opening of this valve and how it adjusts the opening by itself? Do I need to enter the percentage and then manually adjust it to this opening? Because I have little on-site experience with the valve, I don’t know whether it can achieve fast opening and closing at a fixed time/reach a fixed opening.
In fact, this manual adjustment means that each setting of 0 degrees of opening needs to be input manually. For example, the simplest way is to use a secondary control instrument to control the valve. If you switch to the manual input mode, you enter the percentage corresponding to the opening you want, then the valve will turn to the corresponding setting. The opening of the valve automatically forms a PLC loop. You design a parameter. For example, when the material level reaches 2M, the valve opening will be turned to 30%. Then when the material level signal enters the 2nd table, the valve opening will automatically be turned to 30%. You do not need to enter it every time.
In order to achieve a certain control goal in AD, the liquid level could not be effectively controlled, so I had to manually control the controller. However, because the opening of the valve is not a fixed variable, there is no way to directly enter a fixed opening by writing a task. Is there any way to solve this problem? How to implement numerical input for free variables? :L
The valve automatic control process is as follows: The signal from the transmitter is sent to the controller to compare with the set value to obtain the deviation, and then through PID calculation, the corresponding MV value is obtained and sent to the site to control the opening of the regulating valve (positioned by the positioner). Manual control is to directly input the MV value to control the opening of the valve.
The percentage is its opening: loveliness:
Personally, I think there are three ways to adjust the opening of the control valve. One is automatic adjustment. Automatic adjustment is usually combined with other signals.* * together, give a simple example: The valve automatically adjusts to open when the liquid level is low, and conversely automatically closes or reduces the opening when the liquid level is high. The second type is controlled by 4~20mA current signal. 4~20 corresponds to 0~100% opening. You can open as much as you want. Another method is to use air pressure signals to control (sometimes it can be used, but it is rarely used). This method is to set the on-site positioner to manual, and use a pressure reducing filter to directly control the size of the air source to output to the valve to control the opening.~