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Pneumatic Valve Actuators

Introduction

Pneumatic valve actuators are used across various industries to control different types of valves. The term "pneumatic" refers to their utilization of compressed air, making them a widely adopted and reliable technology for valve automation. These actuators can be used to operate valves with on/off control or with a more precise modulating control.



What Are Pneumatic Valve Actuators?

Pneumatic rotary actuators are commonly used to convert compressed air pressure (in the form of a cylinder stroke) into an oscillating rotary motion. Typically operating at 80 psig (5.5 bar) air pressure, these actuators utilize dual internal pistons to achieve motion conversion. Like other pneumatic components, they are durable, offer simplicity and high force for their size, and can operate in hazardous environments. Their versatility is evident in their wide range of torque sizes, ranging from miniature actuators with 72 lb-in torque to larger sizes capable of handling up to 39,000 lb-in torque.


Rotary Pneumatic Valve Actuators

Quarter-turn rotary actuators are widely employed in applications where valves must be operated through a 90-degree rotation. They are designed to provide swift and efficient actuation, making them ideal for quick on/off control or for emergency shut down applications. For rotary pneumatic actuators, the most common design is the rack and pinion type actuator. It utilizes a rack and pinion mechanism to convert the piston’s linear motion into a 90-degree rotary motion, with consistent torque throughout the valve's turning angle. In addition to the standard 90° rotation, rotary actuators are also available in 120°, 135°, and 180° rotation. The rack and pinion actuator is renowned for its reliability and long service life, making it suitable for applications in process industries, manufacturing, and water treatment plants.


Key Features and Characteristics

Pneumatic valve actuators boast several key features and characteristics that enhance their performance and durability. Many of these actuators come equipped with hard anodized aluminum housings, for enhanced appearance and increased resistance to corrosion. Additionally, stainless steel housings are available for environments with high corrosive potential, providing an added layer of protection and durability.



Furthermore, pneumatic valve actuators are available in two primary configurations: double acting and spring return types, spring return is also known as single acting. Double acting actuators require air pressure to enable motion in either direction. Conversely, spring return actuators utilize internal springs, which compress during the air power stroke and then return the actuator to its original position under spring force. This feature proves highly beneficial for fail-safe scenarios and specific control applications, ensuring operational reliability and safety. Additionally, the number of springs in the actuator can be adapted to the available control pressure.


How Pneumatic Valve Actuators Work

The operation of pneumatic valve actuators is based on the fundamental principle of converting air pressure into mechanical motion. When compressed air is introduced into the actuator, it exerts force on the two internal pistons, driving the actuator's rotary motion. The actuator's motion, in turn, is transmitted to the valve's stem or actuating mechanism, causing the valve to open or close as required. This simple yet effective working principle allows for precise control of fluid flow and seamless automation of valve operations.



Internal Components and Their Functions

Rack and pinion rotary actuators use a cylinder piston attached to a rack gear. When actuated, the piston and rack move in a linear fashion rotating the pinion gear and output shaft. A double rack unit utilizes two racks on opposite sides of the pinion gear, in effect, doubling the output torque of the unit.


Rack and pinion rotary actuators also have adjustable stops. The end positions can be configured between 0° and 90° as well as from + 5° to -5°, whereby the valve can be optimally adjusted



Control Methods

Pneumatic valve actuators support different control methods to cater to various operational needs. The two primary control methods are:


Air Control

In standard configuration, double acting pneumatic actuators use compressed air to open and compressed air to close. Spring return actuators use air to rotate and compress springs, and then spring force to rotate when air is removed.

Bleed control accessories can be used to control the speed of rotation on pneumatic actuators.


On/Off Control

In on/off control, the actuator utilizes a pilot solenoid valve accessory open or close a valve based on a voltage signal. This method is commonly used for simple applications where the valve must be fully open or closed without intermediate positions.


Modulating Control

Modulating control, on the other hand, allows the actuator to precisely adjust the valve's position, offering intermediate positions to regulate fluid flow. This method is ideal for applications that require precise flow control. This is accomplished by adding a Pneumatic or Electro-Pneumatic Positioner accessory. These positioners control the position by using very low pressure air or a low power electrical signal. Typical control types are a 3-15 psi pilot air input or a 4-20 mA electrical signal.


The versatility of pneumatic valve actuators, with their fast action, low cost, and reliability make them a preferred choice for numerous industrial applications.


Pneumatic Actuator Accessories

Limit Switch Boxes / Signal Units

Pilot Solenoid Valves

Pneumatic Positioner, Electro Pneumatic Positioner and 3-Position Control

Manual Override



Applications of Pneumatic Valve Actuators

Pneumatic valve actuators find widespread applications in diverse industries, from oil and gas to water treatment, power generation, process automation, snow making, and chemical & pharmaceutical production. Their versatility, reliability, fast operation, and precise control capabilities make them IDEAL components for efficient fluid flow regulation in modern industrial processes. We discuss these various applications of pneumatic valve actuators in greater detail below.


Pneumatic valve actuators are a reliable and low cost method to actuate valves when compressed air is available. Process automation across manufacturing and industrial sectors is the widest use for pneumatic valve actuators. Other industries which commonly used pneumatic actuator are the oil & gas industry, water treatment industry, and chemical/pharmaceutical industry.


The winter sports industry utilizes pneumatic valve actuators for snow-making applications. These actuators are employed in ski resorts and winter sports areas to control the flow of water and air in snow-making machines. Pneumatic actuators are able to use the compressed air that is normally available for atomizing water in the snow making process.


Advantages of Pneumatic Valve Actuator

Pneumatic valve actuators offer many advantages that cater to the needs of modern industries. Their energy efficiency, precise control, remote monitoring capabilities, reduced maintenance requirements, and compatibility with digital systems make them indispensable components for enhancing industrial processes, promoting sustainability, and embracing the digital era of manufacturing and automation.


Reduced Maintenance Requirements

Pneumatic valve actuators are known for their robustness and durability, leading to reduced maintenance demands. The absence of electrical components susceptible to wear and tear contributes to their reliability and extended service life. Additionally, the relatively simple design of pneumatic actuators means fewer moving parts, reducing the likelihood of breakdowns and the need for frequent maintenance. Reduced maintenance requirements translate to lower downtime and associated costs, making pneumatic valve actuators a cost-effective and reliable solution for critical industrial processes.


Initial Cost and Installation

One of the primary advantages of pneumatic valve actuators is their initial cost. Almost all factories have available compressed air making these actuators the better choice over electric valve actuators.



Environmental Advantages

Pneumatic valve actuators have the great advantage of being able to operate safely in hazardous areas, with explosive gases present. As a result, pneumatic actuators can be certified to meet ATEX and NEMA 7 Explosion Proof Requirements.


Potential Reliability Issues and Contingency Plans

Pneumatic actuators are highly reliable with long life. They are easily serviceable when necessary with inexpensive replacement seal kits. While pneumatic valve actuators are generally robust and reliable, certain factors, such as contamination of compressed air or wear and tear of mechanical components over time, can lead to potential reliability issues. Regular maintenance and inspection are essential to promptly identify and address any emerging problems. Additionally, contingency plans, such as backup actuators or manual override systems, are crucial to ensure continuous process control in case of unexpected actuator failures or maintenance requirements.


Key Takeaways

●Pneumatic valve actuators are essential for various industries to control valve openings and closures. They convert air pressure into mechanical motion, precisely regulating fluid flow.


●Their versatility and efficiency make pneumatic valve actuators a preferred choice in critical sectors, including oil and gas, water treatment, power generation, process automation, snowmaking, and chemical & pharmaceutical production.


●The advantages of pneumatic valve actuators include energy efficiency, fast acting, precise control capabilities, remote monitoring features, reduced maintenance requirements, and seamless integration with digital systems and Industry 4.0 technologies. Pneumatic actuators are versatile, economical, and offer a wide range of torque values.


●Overall, pneumatic valve actuators remain indispensable in modern industries, driving efficient and sustainable fluid flow regulation.

Link to accessories catalog.




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