How Direct Acting and Reverse Acting Control Valve Loops Work

A typical control valve loop consists of four basic elements for consideration:

(a) The process under control mainly flow or pressure applications

(b) The process controller that initiates control action to the control valve

(c) A valve positioner (almost always required in most applications)

(d) Control valve action. See How a typical Control Valve Loop Works

These basic elements work in coordination to produce the desired control outcome. Control valve loops can be operated in two basic modes :

(a) Direct acting loops

(b) Reverse acting loops

Direct Acting Control Valve Loops:

In a direct acting control valve loop shown below:

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