Flow-Tech: Industrial Control Valve Basics

FlowTechOnline
31 Dec 201503:44

Summary

TLDRThis video explains the workings of control valve actuators, which regulate fluid flow by varying the orifice size in a valve. The control valve has two main components: the valve body, which houses the fluid connections and restrictor, and the valve actuator, which moves the restrictor to adjust flow. Three types of actuators are discussed: spring and diaphragm, solenoid, and motor-based. Each method controls the valve differently, using pneumatic signals, magnetic fields, or motorized movements, to manage fluid flow for various applications, including both on/off and proportional control modes.

Takeaways

  • 🔧 Control valve actuators regulate fluid flow in a pipe by varying the orifice size.
  • 🏗️ Control valves have two major components: the valve body and the valve actuator.
  • 💧 The valve body contains the fluid connections and the movable restrictor that controls fluid flow.
  • ⚙️ The valve actuator moves the restrictor to adjust the flow of fluid.
  • 🔩 There are three types of actuators used in control valves: spring and diaphragm, solenoid, and motor.
  • 🌬️ Spring and diaphragm actuators use a pneumatic signal to exert pressure on the diaphragm, which moves the restrictor.
  • 📏 The 3-15 psi pneumatic signal controls the restrictor’s position and the flow rate through the valve.
  • ⚡ Solenoid actuators use current to generate a magnetic field, moving the valve to fully open or fully closed positions.
  • 🔄 Motor actuators provide proportional control using a gear motor and a servo amplifier to adjust the valve's position.
  • 🔙 Feedback mechanisms, like wiper arms, help the motor actuator maintain precise positioning by monitoring signals.

Q & A

  • What are the two main components of a control valve?

    -The two main components of a control valve are the valve body and the valve actuator.

  • What role does the valve body play in a control valve?

    -The valve body provides the fluid connections and houses a movable restrictor, consisting of a valve stem and plug, that varies the flow of fluid.

  • How does the valve actuator affect fluid flow in a control valve?

    -The valve actuator physically moves the restrictor, adjusting the orifice size to control the flow of fluid through the valve.

  • What are the three types of actuators used in control valves?

    -The three types of actuators used in control valves are spring and diaphragm, solenoid, and motor actuators.

  • How does the spring and diaphragm actuator operate?

    -A spring and diaphragm actuator uses a 15 psi pneumatic signal to apply pressure on the diaphragm, which exerts a downward force on the spring, moving the valve stem and plug to adjust fluid flow.

  • What happens in a spring and diaphragm actuator when no air pressure is applied?

    -With no air pressure, the spring pushes the restrictor upward, causing the valve to act as a normally open control valve.

  • What is the purpose of a current-to-pressure transducer in a spring and diaphragm actuator?

    -A current-to-pressure transducer is used to provide a 3 to 15 psi signal to the diaphragm, allowing for proportional control of the valve's flow based on the applied pressure.

  • How does a solenoid actuator control the valve?

    -A solenoid actuator uses a magnetic field generated by current applied to a coil, which moves the plunger to open or close the valve for on/off control.

  • How is variable valve positioning achieved using a motor actuator?

    -Variable valve positioning is achieved using a motor actuator by utilizing a gear motor and a servo amplifier. The servo amplifier provides a DC control signal to adjust the valve position, with feedback from a wiper arm that monitors the valve's position.

  • What is the role of the servo amplifier in motor-operated valves?

    -The servo amplifier drives the motor until the control signal is equal to the feedback signal from the valve position, ensuring precise positioning.

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Related Tags
Control ValvesValve ActuatorsFluid ControlSpring DiaphragmSolenoidMotor ControlFlow RegulationPneumatic SystemsProportional ControlServo Amplifier