Introduction
Valve actuators may not be the first thing you think of when it comes to industrial processes, but they are absolutely essential. Picture this: A valve actuator is what you want to control the flow of a fluid through a valve without physically turning it every time. These devices automate valve operation over a wide range of settings from massive power plants to delicate laboratory processes. Different valve actuator types exist for different applications and control needs. In today’s article, we’ll look at these different types of actuators and explain the key differences between them and how to pick the right one for your specific requirements.
If you’re in power generation or fluid control, knowing the different types of valve actuators will help you make an informed decision. And, after all, choosing the right valve actuator can help improve reliability, reduce maintenance costs and make sure your system works well. So let’s dive right in!
What Is a Valve Actuator?
In essence, a valve actuator is a mechanical device that automatically moves a valve to a specific position in response to a signal from a control system. Imagine it as a robotic hand that adjusts your control valve without having to do anything. The force and movement which is required to open or close a valve stem to control the flow of liquids or gas.
Each type of valve actuator has its own purpose and own strengths and weaknesses. There’s an actuator that will fit the bill whether you need rapid action, high precision, or the ability to operate in high temperatures.
Valve actuators are generally classified by motion type and power source. Knowing these classifications will help you decide which actuator valve type is best for your particular needs, whether linear motion or rotary motion and whether the actuator is powered by electric power, compressed air or hydraulic fluid.
Classification of Valve Actuators by Motion Type: Rotary vs. Linear
Valve actuator types are primarily classified based on their motion type: rotary and linear. This classification is basic to know how various actuators work and which valves are appropriate for them.
Rotary actuators give a rotary motion and are mostly used with ball valves, butterfly valves and plug valves. These actuators are intended to rotate the valve stem to a certain degree, typically 90 degrees, to either open or shut the valve. Rotary actuators are used for their fine control and compact size.
Linear actuators, however, provide straight line motion and take least space when fully contracted. These are used with globe valves, gate valves, and other linear valves most of the time. The control of the valve opening requires the movement of the valve stem in a straight line, which is provided by the linear actuators. They are able to produce high levels of pressure and are well suited to applications where a precise shut off is needed.
The decision of which type of actuator to use, rotary or linear, depends on the type of valve and the application that is being used. For example, rotary actuator is suitable for controlling flow in a pipeline using ball valve while linear actuator is suitable for operating a gate valve in a water treatment plant.
However, it is important to point out that there are more developed valve actuator types which can generate both rotary and linear movements. These hybrid actuators provide more flexibility and can be advantageous in systems where flexibility is a major consideration.
Classification of Valve Actuators by Power Source
Actuators can also be categorized by the power source they utilize. Let’s explore the three main categories—pneumatic, hydraulic, and electric actuators—and see how they stack up from different angles, including their strengths, weaknesses, and best-use scenarios.
Pneumatic Actuators: Fast, reliable, and cost effective.
Compressed air is used as a power source by pneumatic actuators. The basic principle is to use a piston or diaphragm actuator that moves in relation with changes of air pressure. The piston moves when air is introduced into the actuator chamber, and the valve is operated. Double acting pneumatic actuators use air pressure for both opening and closing the valve, while single acting types use air for one direction and a spring for the return motion.
Pneumatic actuators have the advantage of fast response time, simplicity and reliability. Fast actuation makes them a perfect choice for high cycling applications. This comes from their simple design with fewer moving parts, which means that lifespan and maintenance will be a long time coming. Pneumatic actuators are also inexpensive in terms of initial investment and long term operational expenses.
However, these actuators have their limitations. They require a consistent air supply facilities therefore require a reliable compressed air system. In very cold environments, there is a possibility that moisture in the air lines freezes and could impact the performance of the actuator.
Ball valves, butterfly valves and plug valves are often associated with pneumatic actuators. Particularly in food and beverage processing, chemical manufacturing and pharmaceutical production industries, quick and reliable operation of these valves is critical. They’re also found in oil and gas facilities, power plants and water treatment facilities.
Hydraulic Actuators: Power and Precision for Heavy-Duty Applications
Hydraulic actuators utilizes pressurized hydraulic fluid to create force and a movement. The working principle is that hydraulic pump pressurizes the fluid then it is diverted into the cylinder. Operating the valve, the piston in the cylinder moves by the pressure of the fluid, thus pulling the piston on the valve stem by a connecting piston. High force output combined with precise control because of the incompressibility of hydraulic fluid.
The main advantage of hydraulic actuators is their ability to generate high levels of force from a small package. Their high power density lets them easily operate larger valves or valves under higher pressure. The incompressibility of the fluid also makes hydraulic actuators excellent for valve positioning with excellent precision. In certain applications where energy efficiency is beneficial, they can hold valve position with no continuing power input.
However, hydraulic systems are costly in terms of system complexity and cost because they require a separate hydraulic power unit. Hydraulic fluid leaks can also be a problem in environments where cleanliness is important, and there’s also the potential for leaks. Hydraulic systems require more maintenance than that of other actuator types.
Large gate valves, globe valves and ball valves are commonly used with hydraulic actuators. They are especially well suited for heavy duty applications in the oil and gas, mining and heavy manufacturing industries. Hydraulic actuators are used in offshore platforms, refineries and large scale water management systems where high forces are needed to operate valves under harsh conditions.
Electric Actuators: Simple, Clean, and Ideal for Precise Control
An electric motor is used to generate the force necessary to operate valves using an electric actuator. Most often the motor’s rotational motion is either converted to linear with the use of a gear system and a lead screw or equivalent system. The valve stem is then actuated to open or close the valve through this motion. Advanced control electronics are incorporated into many electric actuators for precise positioning and feedback.
Their ability to provide precise control and position, clean operation without air lines or hydraulic fluids and easy integration into modern control systems are the key advantages of electric actuators. Generally sufficient sophistication automation with remote operation, and often with detailed feedback of valve position and operational status. Power requirements for electric actuators are also flexible with electric actuators available in a range of voltages and power ratings.
Electric actuators, however, have some limitations. Specialty rated explosion proof actuators may be required in potentially explosive atmospheres, adding to costs. Electric actuators should not be considered as the most economical selection for very large valves, or those requiring high forces. Electric actuators are also dependent on duty cycles, with some limiting the number of times they can be cycled without overheating.
Versatile, electric actuators can be used with all types of valves, including ball valves, butterfly valves, globe valves and gate valves. In particular, these systems are very well used in industries where cleanliness is especially important, such as in pharmaceutical manufacturing, food processing and in water treatment. In HVAC systems, power plants, and chemical processing facilities, where precise flow control and integration with automated systems are important, electric actuators are also widely used.
Here’s a concise summary of the key characteristics, advantages, and applications of the three main valve actuator types:
| Actuator Type | Working Principle | Advantages | Disadvantages | Common Valve Types | Industries |
| Pneumatic | Compressed air moves piston/diaphragm | Fast, reliable, cost-effective | Requires consistent air supply | Ball, butterfly, plug | Food & beverage, chemical, pharmaceutical |
| Hydraulic | Pressurized fluid moves piston | High force output, precise | Complex system, potential leaks | Gate, globe, ball | Oil & gas, mining, heavy manufacturing |
| Electric | Electric motor drives gear system | Precise control, clean operation | Higher cost for explosion-proof models | Ball, butterfly, globe, gate | Pharmaceutical, food processing, HVAC, water treatment |
How to Choose the Right Valve Actuator for Your Application
Choosing the right valve actuator for your application is also about selecting the right valve actuator, but considering a number of important factors to help ensure optimum performance and efficiency.
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Motion Requirements and Type of Valve: The first thing to understand is the type of valve and its motion. For example, ball or butterfly valves with rotary valves need actuators that generate linear torque output or rotational movement. Actuators for linear valves, such as gate or globe valves, must provide linear motion of a piston. Seamless operation requires that the actuator’s motion be aligned with the valve’s desired position.
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Power Source Availability: Assess the available power supply at your site next. Some actuators need an external power source, such as ac motors or pneumatic systems, while others are operated manually. Manual actuators with a hand wheel may be the best choice if your location has no reliable power. For automatic systems, think solenoid valves or hydraulic depending on your supply pressure and system requirements.
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Torque and Force Needs: You need to also figure out the amount of torque or force enforcing the valve to move. The actuators have different levels of force. For example, piston actuators can handle higher pressures and provide enough torque for heavy duty operations. The actuator must provide sufficient force to manage the process fluid flow rate and valve size, which must be subject to flow rate control and also be deflected to a minimized extent.
By paying attention to these key points, you can choose a valve actuator that matches your operational needs perfectly, and will provide long term reliability and efficiency.
Conclusion
Knowledge of valve actuator types is essential for good process control and efficient plant operation. Each response type, pneumatic actuators to power hydraulic actuators and the precision of electric actuators, has its own advantages in specific applications.
Vincer is a well known manufacturer in the electric and pneumatic valve industry with innovative solutions and reliable products. Vincer has years of experience of providing robust and economical actuator systems adequate to various industrial needs. Visit Vincer’s website today for more information on how Vincer can help your operations! To get an inside look at Vincer’s advanced manufacturing processes and state-of-the-art facilities, check out the factory tour video below: