Parts of a Control Valve

In this lesson, we will study the working of different parts of a control valve (CV).

Note- we will use CV for the Control valve.


The diaphragm is the most important part of a control valve. Spring remains on the diaphragm. Air firstly come on diaphragm then applied to spring. If Diaphragm is damaged CV does not work. The diaphragm is damaged due to access air applied to the CV.

Parts of control valve

O- Ring

O- Ring is used to prevent air leakage.


Spring is used to provide movement to a CV. On apply air, the spring is compressed and the CV is operated.


The wheel is used for manual or auto operation of a control valve.


Coupling is used to connect the actuator to the body of a CV.


A plug is the most important part of a control valve body. The seat remains in the plug. The lower smooth part of the plug is known as a seat.

Plug Stem:

Plug stem is also known as a spindle. The plug stem is connected by coupler to the actuator through this plug stem.


The seat is an important part of a CV body. When the control valve is fully closed it is Used to prevent the leakage. It means when a seat is damaged control valve will leakage on full closed.

 Balancing  Ring:

Balancing Ring is made up of Teflon or metal (Graphite), depending on the class of CV. A balancing Ring is also used to prevent leakage from the CV body.

 Bonnet :

Bonnet is the Outer cover Of a CV Body.


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