Automatic control valve
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For automatic control valves, when they carry out their functions, is it the DCS system that controls them, or do they have the ability to adjust on their own? I’m referring to the automatic mode: for example, when the flow rate fluctuates greatly, the valve needs to open and close repeatedly. What gives the instructions for these opening and closing actions?
After the system is prepared in advance, the DCS issues the command
The operation of the control valve is regulated based on the magnitude of the current output by the DCS or PLC; the standard signal is 4–20 MA. The DCS or PLC contains PID calculation modules, which perform specific calculations using the values of PV and SP. Finally, this results in a current signal that is used to control the valve
It is generated by the control system, that is, output by the control section in the DCS....
Using flow rate as the sensing signal, a corresponding current is output based on the magnitude of the flow rate
It’s better to install a self-acting flow control valve: L