Problems with the pressure control circuit?
Thread Content
Regarding the pressure control circuit on the pipeline, what considerations determine whether the valve should be placed before or after the pressure transmitter? Can it be placed anywhere? Because this will affect the selection of the controller’s positive and negative actions. . .
I think it depends on whether the pressure to be controlled is before or after the valve. If the pressure is to be controlled before the valve, then you need to choose a direct-acting type; if it’s after the valve, then you need to choose a reverse-acting type. That’s what I think
Whether the valve is placed before or after the pressure transmitter, my understanding is that it depends on the control process. For example, in a temperature and pressure reduction system, it is necessary to control the outlet pressure, and the pressure measurement point is naturally placed after the control valve. Another example is the pressure holding and release system, which requires controlling the pressure inside the pipeline; the pressure point is located before the control valve.
In a pressure control circuit, there is no explicit requirement specifying whether the control valve must be installed upstream or downstream; therefore, it mainly depends on the control requirements of the process. My personal opinion is that one can follow the method used for installing control valves when measuring flow rate with orifice plates, that is, the orifice plate should be installed before the control valve!
Whether the measurement points are located before or after the valve is determined based on process requirements
The flow control valve is installed after the flow rate; as for pressure control, it depends on the requirements of the process – it may be before or after the valve. Specific examples are given in what was said on the 3rd floor