control valve

CONTROL VALVE

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Control Valve

Most common final control element in process control

industries.

Manipulates a flowing fluid, such as gas, steam, water, or

chemical compounds.

FUNCTION

Compensate the load disturbance and keep the regulated

process variable as close as possible to the desired set point.

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Control Valve Assembly

It consists of,

Valve body Internal trim parts Actuator Positioner

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Major Parts of Control Valve BodyValve plug stem

Bonnet

Valve plug (Closure Member)

Valve body

Cage

Seat ring

Flange

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Parts of Control Valve BodyBonnet: The portion of the valve that contains the packing box and can

guide the stem.

Trim: The internal components of a valve that modulate the flow of the

controlled fluid is called trim. Trim would typically include,

• Closure member

• Seat ring

• Cage

• Valve stem 

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Closure Member (Valve Plug): It is the movable part of the

valve that is positioned in the flow path to modify the rate of

flow through the valve.

Seat Ring: The seat ring is normally clamped between the

upper valve body and the lower valve body in split valve

constructions.  

Cage: It is a part of a valve trim that surrounds the closure

member and can provide flow characterization.

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Various Cage Styles

QUICK OPENING LINEAR EQUAL PERCENTAGE

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Valve Stem: In a linear motion valve, the part that connects the

actuator stem with the closure member is called valve stem.

Flange: A part that closes a valve body opening opposite the

bonnet opening. It can allow reversal of the valve action.

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Valve Body: Provides the pipe connecting ends, the fluid flow

passageway, and supports the seating surfaces and the valve

closure member.

The most common valve body constructions are:

• Single-ported valve bodies having one port and one valve plug.

• Double-ported valve bodies having two ports and one valve plug.

• Two-way valve bodies having two flow connections, one inlet

and one outlet.

• Three-way valve bodies having three flow connections.

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Common Valve Body Constructions

Three-Way Valve with Balanced Valve Plug Double-Ported Valve Body

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