PCV Valves vs. FCV Valves

Both PCV and FCV, we regulate pressure and flow. But the Objective of PCV is to control the pressure and is designed to handle min. and max. pressure limits. where as FCV will regulate the flow within min. and max. flow limits.

The other difference is that pressure signal is fedback to the PCV and flow signal is fedback in FCV.

from valve design and fluid mechanics point of view , they are the same. both are taking DP across the valve in different flow conditions. from control point of view the PCV closing and openning due to pressure values of the process variable compared to the pressure set point but the FCV is openning and closing due to flow process variable compared to flow set point.

Hi there,

It will depend on your process medium - this will determine the type of valve you select i.e. Globe, Butterfly etc.

If you are trying to control the pressure/flow of a gas for example you would probabely be using a butterfly type valve. This is a generalisation as you would need to know flow rates, permissable pressure drops etc etc.

If you were trying to control the flow/pressure of a clean process liquid, water for example - you would probabely use a globe valve. Again, a generalisation as you need to know what the permitted process conditions are.

A good place to start would be the fischer control valve handbook. It is freely downloadable (do a google search) - I think you can get it from the Emmerson web site.

It should give you a good idea on control valve selection for diffrent medium types.

There is one other thing to bear in mind - the valve characteristic. Usually, but not always a flow control valve will have a linear characteristic, while a pressure control valve will have an equal percentage characteristic.

Regards,

Craig