Pressure Control Valve vs Flow Control Valve

[neroverdi41]

Hello friends;

I wanted to investigate the difference between these two valves, but I couldn't find any clear information. is something added on top of a normal control valve? can you inform me about this?

 

[LittleInch]

There is no difference in the valve itself and I've always just called them control valves.

You can use any number of parameters to control the position of the control valve not just flow or pressure, but also level, temperature, hand position, or any variable you can measure.

Many valves have multiple inputs into the same valve, you just run it through a low selector block to choose the parameter which close the valve more than any other.

 

[neroverdi41]

There is no difference in the vane itself and I've always just called them control valves.

You can use any number of parameters to control the position of the control valve not just flow or pressure, but also level, temperature, hand position, or any variable you can measure.

Many valves have multiple inputs into the same valve, you just run it through a low selector block to choose the parameter which close the valve more than any other.

Thank you for your answer.

there is a regulator and positioner in the flow control valve. is there a device other than these in the pressure control valve? what do they adjust the pressure according to? for example, I want to close the valve when the pressure drops to 20 bar. how do I do it?

 

[LittleInch]

The same way, just substitute the signal from the pressure transmitter or sensing line for the flow transmitter.

Depends whether you are wholly electronic or pilot operated.

So electronic, you get a signal from the pressure transmitter in 4-20mA or 1-5V or a digital number. This goes into your PID controller which compares the signal to the set point you've set the valve to. If its higher then it sends a signal to close the valve until the pressure reduces, if less then one to open.

Pilot operated or relay driven works in much the same manner except they use springs and valves to do the same thing. Many water systems are whoilly self contained with no external power source for pressure control. See this e.g. https://www.cla-val.com/wp-content/...orks-How-Automatic-Control-Valves-Operate.pdf

As said, forget about a valve being called a FCV or a PCv or a TCV, it's just a control valve. How you control it is up to you and your instrument engineer.

Many simple controller come with the valve and actuator and all you do is feed it power, sometimes air and a signal from your measing device, then read the manual on how to set it to control what you want.