What is An Actuated Valve? – Working Principle and Types
Valves with actuators form the cornerstone of flow regulation within any contemporary process system. An actuated valve is made to function externally using a mechanically coupled force, which is referred to as an actuator. This piece of writing will examine the operational mechanism of an actuated valve, and diverse varieties of actuated valves, present a diagram, and compare its operation with that of a solenoid valve and a control valve.
How Does an Actuated Valve Work?
Actuated valves generally serve as an on-off device to permit or impede the flow of fluid. At times, they offer a certain degree of partial flow allowance in accordance with the demands of the process. The control of fluid flow is of utmost significance in any modern process system. Actuated valves guarantee that the fluid is properly sealed and distributed across the entire system.
An actuated valve operates by either manual, electrical, pneumatic, hydraulic, self-actuated, or spring force. These valves are typically used in process systems where open and close operations are required.
Engineers are obliged to ascertain that the actuated valve adopts the appropriate actuation approach. For example, manual actuation for a blowoff valve would probably be overly sluggish. Under such circumstances, pneumatic or hydraulic actuation presents a more preferable option on account of a nearly instantaneous reaction speed.
Furthermore, torque and accessibility requisites offer another criterion for selection.
Different Types of Actuated Valves
A variety of distinct types of actuated valves exist, including manual, electrical, pneumatic, hydraulic, self-actuated, and spring valves.
Manually Operated
Manual actuation of a valve, be it through a handwheel, gears, or a lever, is affected by a plant operator. This approach represents one of the simplest forms of actuation. Nevertheless, it becomes impractical in scenarios where valves are located in hazardous areas, is inaccessible to an operator, demand a large number of rotations for opening or closing, or have excessive torque needs. It is generally well-suited for applications in easily reachable, non-hazardous locations with infrequent operational requirements.
Electrically Actuation
This particular type of actuation employs electricity as the principal means of activation. There exist several diverse methods of utilizing electricity to achieve valve opening and closing. In one variant, an electrical actuator maneuvers the valve using an electric motor.
Another approach is to make use of a solenoid to open or close a valve.
A third variety, namely the control valve, enables the precise positioning of the valve within the range from the completely open to the fully closed state in accordance with the modulation of an electrical signal.
Pneumatically Actuated
This actuation approach utilizes gas, or specifically air, to exert external pressure on a piston that is contained within a closed cylinder or on a diaphragm, thereby enabling the valve to be fully opened or closed. The process is managed through circuitry for controlling air signals or via a manual switch.
Hydraulic Actuated Valves
Hydraulic fluid, usually oil, exerts force on a piston to activate the valve. This kind of actuation functions in a way similar to that of the pneumatic one, with the pressure of the fluid generating thrust that acts upon the piston.
Self Actuated Valves
These valves utilize the media within the system to move themselves. In contrast to pneumatic and hydraulic actuated valves, they don’t need any additional input for their operation. The self-actuated valve is rather straightforward and is designed to keep a set-point pressure. Relief valves, safety valves, and check valves all fall into the category of self-actuated valves.
Spring Actuated Valves
The spring-actuated valve is engineered to be used only once. When a predetermined event takes place, like over-pressurization or a power outage, the spring gets released and the valve starts to function. Sometimes, the spring-actuated system can be classified as a form of self-actuation, depending on its specific setup. Nevertheless, the spring actuation might be external to the valve, while the self-actuation setup is entirely self-contained. The spring offers a single-use function since it cannot be reset once it has been used.
Actuated Valve vs. Solenoid Valve
Although a solenoid valve is technically considered an actuated valve, its functionality is frequently compared directly to that of an actuated valve.
The word “actuated” implies that the valve can be started up by any method. This is different from fully automatic solenoid valves, which don’t have any manual mechanisms. Their opening and closing are determined by either AC or DC voltage.
Inside the body of a solenoid valve, there exists a small orifice that opens or closes so as to permit or impede the flow. A plunger located within the body causes the orifice to open or close through upward and downward movements. This activates the coil and thus completes the cycle.
Generally speaking, hydraulic, pneumatic, and solenoid actuators offer the quickest actuation. Nevertheless, solenoids are not very practical for large valves as they demand excessive size and power. Moreover, hydraulic and pneumatic actuators need a system to supply hydraulic or pneumatic energy. In either situation, the speed of actuation can be adjusted by fitting appropriately sized orifices in the hydraulic or pneumatic lines.
| Actuated Valve | Solenoid Valve |
| Most options are slower-acting than a solenoid valve | Very fast acting |
| Manual, electrical, pneumatic, hydraulic, self-actuated, and spring | AC or DC supply power in various voltages. |
| High back pressures and high inlet pressure permitted | Back pressure and inlet pressure limitations based on size and design |
| Very high flow rates w/low pressure drop | Lower flow |
| Manual override | No manual override |
Actuated Valve vs. Control Valve
Control valves are a part of the category of actuated valves. A control valve, which is a type of actuated valve, utilizes precise electrical signals to position itself at a specific location, thereby offering a high level of flow control capability. The controller reacts to voltage input by either opening or closing the valve.
A control valve governs and adjusts the flow of a liquid at particular set points. Such set points may cover aspects like density, flow rate, pressure, temperature, or liquid level. It features a valve body as well as an actuator, which is positioned within the body assembly.
In comparison to actuated valves that generally offer a straightforward on/off function, control valves supply precise flow control and may operate in cycles as per the requirements of an integrated PLC (Programmable Logic Controller) control system.
Characteristics of the control valve
- They offer rapid responses.
- A signal is generated by a controller.
- They possess flow characteristics that are directly associated with the opening of the valve.
