Prática de Shadowing: What is a Control Valve? - Aprenda a falar inglês com vídeo
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The control valve receives a signal from a controller, such as a PLC or a DCS, in order to operate.
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The controller compares the actual flow rate to the desired flow value, called the setpoint.
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The controller will produce an output to move the valve to bring the flow rate to the setpoint value.
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A control valve is a power operated device used to regulate or manipulate the flow of fluids,
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such as gas, oil, water, and steam.
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It is a critical part of a control loop and is an example of a final control element.
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The control valve is by far the most common final control element used in industry today.
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A control valve can be operated electrically, pneumatically, or hydraulically.
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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.
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Because the PLC signal is electrical, the control valve may require a device to convert that electrical signal so that it can operate.
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A control valve has two separate components, the valve and the actuator.
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Valve bodies are of different types or styles depending on service conditions, piping layout, and desired application.
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The two classes of control valves are linear motion and rotary motion.
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On a linear motion valve, the stem and valve movement is up and down.
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A common type of sliding control valve is the gate valve.
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A rotary motion valve in almost all cases rotates 90 degrees from open to the closed position.
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A commonly used rotary valve is the butterfly valve.
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The actuator is the device connected to the valve through the valve stem that provides the force required to move the valve.
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As we said earlier, the actuator can be controlled electrically, pneumatically, or hydraulically.
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The most common and the most reliable is the pneumatic actuator.
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The control valve receives a signal from a controller, such as a PLC or a DCS, in order to operate.
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The controller compares the actual flow rate to the desired flow value, called the set point.
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The controller will produce an output to move the valve to bring the flow rate to the setpoint value.
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Because of how pneumatic actuators are built, a control valve will fail to a specific position when a loss of the control signal occurs.
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As the supply air pressure is increased, the rubber diaphragm pushes against the spring and moves the valve stem down into the valve body.
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As the supply air pressure is reduced, the spring will move the valve stem out of the body.
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The position to which the control valve is moved if a loss of signal occurs is referred to as the fail-safe mode.
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The type of fail-safe mode depends on the application for which the control valve is used.
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The actuator causes the valve to close in a fail-closed control valve.
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The actuator causes the valve to open in a fail-open control valve.
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In normal operation, the force of the spring must be overcome by the electrical or pneumatic actuator.
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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.
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You might wonder how much the valve opens or closes when the flow rate changes.
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Well, that depends on a number of things, such as the percentage of flow rate change, and the diameter of the pipe.
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Regardless, the controller must be tuned so that it produces the correct response to any change in flow rate.
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This is most commonly achieved by using PID control within the PLC or controller.
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We have already created several easy to follow videos on what a PID controller is.
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If you want to learn more about this topic, just head on over to realpars.com slash blog.
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Type in PID in the search bar and all the relevant articles and videos will pop up.
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We will also put a link in the description if you are watching this on YouTube or any other social media platform.
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In this video, we have learned
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that a control valve can vary the flow of a liquid or gas used in a process.
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We also learned that a control valve can be one of two main types,
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linear or rotary, and that we can use a fail-safe type of valve in critical areas.
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Finally, we introduced you to how control valves are controlled by the use of PID instructions in the PLC or DCS system.
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Want to learn PLC programming in an easy to understand format and take your career to the next level?
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Head on over to realpars.com Hey!
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Você está praticando inglês com "What is a Control Valve?" usando a técnica de Shadowing.
O que é a Técnica de Shadowing?
Shadowing é uma técnica de aprendizado de idiomas com base científica, originalmente desenvolvida para o treinamento de intérpretes profissionais. O método é simples, mas poderoso: você ouve áudio em inglês nativo e repete imediatamente em voz alta — como uma sombra seguindo o falante com 1-2 segundos de atraso. Pesquisas mostram melhora significativa na precisão da pronúncia, entonação, ritmo, sons conectados, compreensão auditiva e fluência na fala.












