Actuated Valve – Working Principle and Types
Actuated Valve – Working Principle and Types
An actuated valve is a type of valve that is controlled automatically, often remotely, to regulate the flow of fluids (liquids or gases) through a pipeline or system. These valves are typically used in industrial processes where constant monitoring or adjustment is needed, and where manual control would be impractical. Actuated valves are equipped with an actuator, a device that receives a signal to control the valve’s position (open, closed, or partially open/closed).
Working Principle
The working principle of an actuated valve involves three key components:
- Valve Body: The valve body itself (ball, globe, butterfly, or gate valve, depending on the design) is responsible for physically regulating fluid flow. It has an opening that can be enlarged or restricted by moving a valve element (such as a ball, plug, or disc).
- Actuator: This is the mechanism that operates the valve. It receives a signal from a control system or operator, which causes it to either open, close, or adjust the valve to a desired position. Actuators can operate through various power sources like electric, pneumatic, or hydraulic energy.
- Control Signal: The actuator receives a control signal from a remote controller (such as a PLC or DCS) or manual system that dictates the desired valve position.
- In electric actuators, the control signal is usually an electrical input, and the actuator uses electric motors or solenoids to operate the valve.
- In pneumatic actuators, the control signal is typically compressed air, which powers the actuator’s piston or diaphragm.
- In hydraulic actuators, the control signal is a pressurized fluid, such as oil, which moves the actuator’s components.
Types of Actuated Valves
Actuated valves come in various types, each suitable for specific applications and fluid handling needs. The most common types of actuated valves are:
- Ball Valve:
- Working: A ball valve uses a spherical ball with a hole in it. When the valve is open, the hole aligns with the pipe to allow fluid flow. When the valve is closed, the ball rotates to block the flow.
- Common Actuators: Electric or pneumatic actuators are commonly used for ball valves in on/off control systems.
- Applications: On/off services in gas, liquid, and steam systems.
- Globe Valve:
- Working: A globe valve regulates flow by moving a disc or plug over an opening in the valve body. The disc’s position controls the flow rate.
- Common Actuators: Pneumatic or electric actuators are typically used for globe valves to provide precise control of flow.
- Applications: Flow control in process industries, water treatment, and steam systems.
- Butterfly Valve:
- Working: A butterfly valve uses a disc that rotates to control the flow of fluid. When the valve is open, the disc is positioned parallel to the flow, and when closed, it is perpendicular.
- Common Actuators: Pneumatic, electric, or hydraulic actuators.
- Applications: Used for flow regulation in large pipelines for water, oil, and gas systems.
- Gate Valve:
- Working: A gate valve uses a wedge-shaped gate to stop or start the flow. The gate is lifted or lowered using an actuator.
- Common Actuators: Electric actuators are typically used for gate valves in applications requiring full opening or closing.
- Applications: Ideal for isolation applications in water treatment, oil, and gas pipelines.
- Check Valve:
- Working: Check valves allow fluid to flow in only one direction. They automatically close when fluid flows backward.
- Common Actuators: Typically no actuator required, as check valves operate automatically based on the flow direction.
- Applications: Preventing backflow in piping systems.
- Pressure Relief Valve:
- Working: This valve is designed to open automatically when the pressure within a system exceeds a certain preset level, thus relieving excess pressure.
- Common Actuators: Spring-loaded or pilot-operated actuators.
- Applications: Used in pressure vessels, steam systems, and boilers to ensure safe operation.
- Solenoid Valve:
- Working: A solenoid valve is operated by an electromagnet (solenoid) that opens or closes the valve when energized.
- Common Actuators: Solenoid coil that operates on electrical input.
- Applications: Used for controlling small flows of gases and liquids in automated systems, HVAC systems, and process control.
Actuator Types
The actuators themselves can be divided into three main categories:
- Electric Actuators:
- How it works: Electric actuators use an electric motor to turn a valve stem or operate a mechanism that opens or closes the valve.
- Advantages: High precision, ability to provide continuous control, easy integration with electronic systems.
- Applications: Ideal for situations where there is a need for precise, variable control (e.g., in chemical processes or HVAC systems).
- Pneumatic Actuators:
- How it works: Pneumatic actuators use compressed air to drive a piston or diaphragm that moves the valve element.
- Advantages: Fast response time, reliable, and capable of operating in hazardous environments.
- Applications: Common in industries where rapid actuation is necessary, such as in manufacturing or automation.
- Hydraulic Actuators:
- How it works: Hydraulic actuators use pressurized fluid to operate a piston or other mechanical elements that move the valve.
- Advantages: High force output, suitable for large valves or harsh environments.
- Applications: Used in heavy-duty applications, such as oil and gas industries, power plants, or marine operations.
- Manual Actuators:
- How it works: Manual actuators require human effort (like a handwheel or lever) to operate the valve.
- Advantages: Simple, no need for external power source.
- Applications: Used where automatic control is not necessary or in smaller systems.
Applications of Actuated Valves
Actuated valves are commonly used across various industries:
- Oil and Gas: For regulating flow in pipelines, managing pressure, and controlling the flow of hydrocarbons.
- Chemical Processing: For controlling the flow of chemicals in reactors and piping systems.
- Water Treatment: To regulate water flow and pressure in water treatment facilities.
- Power Generation: For controlling steam, water, and other fluids in turbines and boilers.
- HVAC: For regulating air or water flow in heating, ventilation, and air-conditioning systems.
Conclusion
Actuated valves play a crucial role in automating fluid flow control within a wide range of industries. They combine a valve body with a power-driven actuator, making them ideal for processes that require frequent or precise control of fluid flow. Depending on the application, various types of valves and actuators are selected to meet specific needs for safety, reliability, and efficiency in fluid handling systems.
