Name: What is a Control Valve?
Uploaded: 2022-11-11T02:35:07.000Z
Duration: 6 min 13 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

The control valve receives a signal from a controller such as a PLC or a DCS in order to operate.

The controller compares the actual flow rate to the desired flow value called the setpoint.

The controller will produce an output to move the valve

to bring the flow rate to the setpoint value.

A control valve is a power-operated device

used to regulate or manipulate the flow of fluids,

and is an example of a final control element.

The Control Valve is by far the most common final control element used in industry today.

A control valve can be operated electrically, pneumatically, or hydraulically.

A control valve receives a signal from a controller

such as a PLC in order for it to move resulting in a change in flow.

to convert that electrical signal so that it can operate.

A control valve has two separate components:

or styles depending on service conditions,

The two classes of control valves are “Linear Motion” and “Rotary Motion”.

the stem and valve movement is up and down.

A common type of sliding control valve is the “Gate Valve”.

A rotary motion valve in almost all cases

rotates 90° from open to the closed position.

A commonly used rotary valve is the “Butterfly Valve”.

The actuator is the device connected to the valve through the valve stem

that provides the force required to move the valve.

As we said earlier, the actuator can be controlled electrically,

The most common and the most reliable is the “Pneumatic Actuator”.

The control valve receives a signal from a controller

such as a PLC or a DCS in order to operate.

The controller compares the actual flow rate

to the desired flow value called the setpoint.

Because of how pneumatic actuators are built,

a control valve will fail to a specific position

when a loss of the control signal occurs.

the rubber diaphragm pushes against the spring

and moves the valve stem down into the valve body.

the spring will move the valve stem out of the body.

The position to which the control valve is moved

if a loss of signal occurs is referred to as the “fail-safe” mode.

The type of “fail-safe” mode depends on the application

In normal operation, the force of the spring

must be overcome by the electrical or pneumatic actuator.

In the event of a “power failure” to the actuator,

the electrical or pneumatic force is no longer present

and the spring pressure forces the valve to open.

You might wonder how much the valve opens or closes

such as the “percentage of flow rate change”

so that it produces the correct response to any change in flow rate.

This is most commonly achieved by using “PID” control

We have already created several easy to follow videos

If you want to learn more about this topic,

just head on over to “Realpars.com/blog”.

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In this video, we have learned that a Control Valve

can vary the flow of a liquid or gas used in a process.

We also learned that a Control Valve can be one of two main types,

We can use a “fail-safe” type of Valve in critical areas.

Finally, we introduced you to how Control Valves are controlled

by the use of PID instructions in the PLC or DCS system.

Want to learn PLC programming in an easy to understand format