Pressure cv vs. pressure regulator

Please explain to me the difference between pneumatic control valve and pressure regulator valve, especially in the control actuation object.

A pneumatic control valve (also electronic, or digital fieldbus) has an input (setpoint) the desired valve position from a controller output. This value is used to regulate the pressure applied to the valve's pneumatic motor, typically using a source of high pressure instrument air, that opposes a spring and may be either air-to-open or air-to-close, depending on the desired fail-safe direction. The positioning action is proportional to the valve setpoint signal.

A pressure regulator is a somewhat similar device with a fixed setpoint used to keep a line pressure (such as steam or air) at a constant value. The control action is local and usually does not depend on a source of instrument air. In a regulator, the process fluid usually opposes the spring force to move the valve position. Use of a regulator for other than steam or air is unusual.

Dick Caro
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Richard H. Caro, Certified Automation Professional, CEO, CMC Associates,
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