Selecting the right valve actuator is critical for ensuring the efficient and reliable operation of your fluid control system. Valve actuators are the driving force behind the opening and closing of valves, and choosing the appropriate type can significantly impact system performance.
There are dozens of types of valve actuators and valves. There must be a way to operate a valve wherever there is one. There are a variety of ways to do this, including gears, levers, and hand-wheels. However, valve actuators are one of the preferred choices for operating valves as they can be automated to eliminate the need for direct human interactions. Such remote and automatic operation is particularly important in emergency-like scenarios where their shutdown mechanisms can reduce the need for human involvement in dangerous situations.
While safety is frequently the major reason for opting to automate a valve, there are additional benefits as well:
- Need for reliable operation
- Greater control and process system performance
- Valve’s location in an inaccessible or remote area
- Most cost-efficient solution available
Every valve actuator has an input segment that receives the power supply and/or signal, an output, and a mechanism/circuitry that allows it to operate the desired valve. The valve’s quality will depend on its mechanical design, machining, and metallurgy. Its real-world performance in the control loop will depend on the actuator.
1．The introduction of Valve Actuator.
A valve actuator is a mechanical device used to control the opening and closing of a valve. Such as a butterfly valve, ball valve, gate valve, or any other type used in various industrial and fluid control applications. Valve actuators are essential components in fluid control systems. They provide the necessary force or torque to operate the valve, allowing it to regulate the flow of fluids, gases, or other substances through a pipeline or process.
The primary function of a valve actuator is to move the valve’s internal components (such as the valve disc or ball) to open, close, or modulate the flow of the fluid. Actuators come in various types. It can receive power from different energy . Including manual (hand-operated), electric, pneumatic (compressed air), hydraulic (fluid pressure), and even electronic and digital control systems.
Valve actuators are selected based on the specific application. The type and size of the valve, the required operating speed, the environmental conditions, and other factors are important. They are crucial in oil and gas, water treatment, manufacturing, etc.
2．The Functions of the Valve Actuator
All actuators must be able to perform the following tasks:
- Adjust the mechanism of closure (ball, disk, or plug). Actuators must have the appropriate directing controls and provide enough torque/thrust to move the closure mechanism in mild and severe conditions.
- Hold the valve closed in a directed position. Actuators must have the necessary spring, fluid power, or mechanical stiffness to close the valve, even in throttling applications wherein fluids provide excessive torque against it.
- Properly seat the valve.For example, a butterfly valve is considered properly seated when the flap is in a resilient seat or liner.
- Have a sound failure mode. In a system failure disaster, valve actuators must be equipped to be fully opened, closed, or stay as is, depending on the application.
- Capable of performing the required rotation. The majority of valves require rotation of 90 or 180 degrees. The required rotational travel will determine the best valve actuator to use.
Capable of operating under required speed. The cycle speed is used to control the valve actuator.
3.Selecting Valve Actuators
While there are four general types of valve actuators, process engineers will generally find themselves choosing between pneumatically or electrically actuated valves for process systems. While each has advantages, selecting the valve actuator that best matches the application will be determined by many usage factors:
Compatibility (power source)
The available power source should be the initial determinant. A supply of air between 40 and 120 psi is required for pneumatic actuators. Higher air pressures can be difficult to acquire, while lower pressures require a larger piston or diaphragm to create the required operating torque. A 110 VAC power source is typically required for electric actuators. A valve actuator, on the other hand, can be ordered with different-sized AC and DC motors.
While both types have a wide temperature range, pneumatic actuators can operate up to 120 degrees Fahrenheit with the right seals, bearings, and grease. In contrast, electric actuators can withstand operations at below -40 degrees Fahrenheit.
An electric valve actuator is sometimes difficult to justify in a hazardous setting, yet it may be required owing to a lack of compressed air or the inability of the pneumatic style to perform as required. If this is the case, an electric valve actuator must be protected from explosions by a NEMA VII cage. Because pneumatic actuators are referred to as ‘explosion-proof,’ they are a more practical option.
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