Different Types of Valve Actuators Working Principles and Benefits

Explore different types of valve actuators, their working principles, advantages, and applications to select the ideal actuator for your projects.

If you’re involved in process control or plant maintenance, you know that valve actuators are the backbone of reliable automation. Choosing the right valve actuator type—whether electric, pneumatic, or hydraulic—can make or break system performance, safety, and efficiency. From oil & gas to water treatment and pharma, each actuator offers unique strengths and trade-offs that engineers must understand before committing. In this guide, you’ll get a clear, no-nonsense overview of the different types of valve actuators and their working principles, practical pros and cons, and real-world applications. Plus, we draw on DELCO’s 20+ years of expertise to help you pick the perfect actuator for your next project or retrofit. Let’s get straight to the heart of valve automation in 2025.

What Is a Valve Actuator? Basic Definition and Function

A valve actuator is a mechanical device that automatically moves a valve to control flow in a pipeline. It converts a control signal (electric, pneumatic, or hydraulic) into valve movement—either opening, closing, or modulating the valve position.

Manual Valves vs Actuated Valves

Feature	Manual Valve	Actuated Valve
Operation	Hand-operated (handwheel, lever)	Automated by actuator (electric, pneumatic, hydraulic)
Speed	Slow, operator-dependent	Fast and consistent
Remote Control	Not possible	Fully remote and automated
Safety	Limited (requires human presence)	Enhances process safety via fail-safe modes
Precision	Limited to operator skill	High precision with feedback systems

Role in Process Safety, Efficiency, and Remote Operation

Valve actuators play a crucial role in industrial automation by:

• Improving safety through fail-safe designs that close or open valves during emergencies without human intervention.
• Boosting efficiency by enabling fast, precise, and repeatable valve positioning, optimizing flow control.
• Allowing remote operation to reduce personnel exposure to hazardous environments and enable centralized process control.

In modern industrial setups, actuated valves are essential components of valve automation systems, providing reliable control and integration with Distributed Control Systems (DCS) and Programmable Logic Controllers (PLC).

For example, DELCO electric valve actuators deliver precise positioning with built-in torque monitoring, improving both safety and process reliability on US industrial sites.

How Do Valve Actuators Work? General Working Principle

Valve actuators work by converting an input signal into mechanical motion that moves the valve stem, changing the valve’s position to regulate flow. The process starts with a control signal—either electric, pneumatic, or hydraulic—sent to the actuator. The actuator then moves the valve stem either to open, close, or modulate the valve position, controlling the fluid or gas flow through the pipeline.

This basic flow can work in two main control modes:

• Open-loop: The actuator moves based only on the input signal, without feedback. It assumes the valve reached the correct position but doesn’t verify it.
• Closed-loop: The actuator uses a positioner or feedback system to monitor valve position in real-time. If the valve deviates from the signal command, the system adjusts the actuator automatically to ensure precise control.

Closed-loop control with valve positioners provides higher accuracy and reliability, especially important in critical process controls where exact valve positioning impacts safety and efficiency. This makes automated valve operation systems far superior to manual control in many industrial setups.

Electric Valve Actuators: Working Principle and Types

Electric valve actuators work by converting electrical energy into mechanical motion using a motor connected to a gear train. This setup drives the valve stem to open or close the valve. Built-in limit switches stop the motor at the desired position, while torque switches prevent damage by cutting power if resistance gets too high.

There are two main types of electric actuators:

• Multi-turn actuators: These rotate the valve stem multiple times, ideal for globe valves or other linear valves.
• Quarter-turn actuators: These rotate the stem 90 degrees, suitable for ball or butterfly valves.

Electric actuators are popular because they offer precise valve control without the need for air or oil supplies, making them clean and low maintenance. They easily integrate with control systems like DCS and PLC for seamless automation. However, their higher upfront cost and dependence on electric power mean they aren’t fail-safe unless paired with a battery backup.

In U.S. industrial settings, electric actuators are widely used for reliable valve automation, including key models like the DELCO electric series, which is designed for tough environments requiring precise control and durability.

Pneumatic Valve Actuators and Their Working Principle

Pneumatic valve actuators use compressed air to generate motion that opens or closes a valve. The most common types include diaphragm and spring actuators or piston-driven rack and pinion designs. In the diaphragm and spring model, air pressure pushes against a flexible diaphragm, moving the valve stem against a spring force—this is typical in single-acting (spring-return) actuators. Double-acting pneumatic actuators use air pressure on both sides of a piston to move the valve stem in either direction, providing more control but requiring air supply for both open and close strokes.

Single-acting vs Double-acting Pneumatic Actuators:

• Single-acting actuators use spring force to return the valve to its default position when air is off, providing a fail-safe feature.
• Double-acting actuators rely solely on air pressure for movement in both directions, allowing faster response but no automatic fail-safe action without external controls.

Pros of Pneumatic Actuators:

• Intrinsically safe for hazardous environments since they don’t use electrical power.
• Fast response and quick cycling make them ideal for processes needing rapid valve operation.
• Fail-safe operation in single-acting types due to spring return.

Cons:

• They require a supply of clean, dry compressed air, which can add to maintenance and operational cost.
• Limited stroke force compared to hydraulic or electric actuators, which can restrict their use on very large or high-torque valves.

Scotch Yoke vs Rack & Pinion

Two popular mechanical designs in pneumatic actuators are scotch-yoke and rack & pinion.

• Scotch-yoke actuators convert linear piston movement into rotary motion via a sliding yoke. They offer smooth, high-torque output and are excellent for quarter-turn valves like ball or butterfly valves.
• Rack & pinion actuators use a piston-driven rack that turns a gear (pinion), rotating the valve stem. They provide precise control, compact design, and durability in tough applications.

Choosing between these depends on torque requirements, valve type, space constraints, and speed needs. For example, rack & pinion actuators are often favored for efficient, repeatable control in industrial settings.

For a practical example of pneumatic valve automation, many operators use models comparable to the stainless steel flanged foot valve to ensure reliable flow control with pneumatic actuation.

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This breakdown highlights why pneumatic valve actuators remain a staple in industries that prioritize safety, speed, and fail-safe operation while balancing air supply logistics.

Hydraulic Valve Actuators

Hydraulic valve actuators use fluid pressure to generate powerful movement, typically through a hydraulic cylinder or a rotary vane system. When pressurized oil enters the cylinder or rotary chamber, it pushes a piston or vane that moves the valve stem, opening or closing the valve.

Pros:

• Deliver the highest force and torque, making them ideal for large valves and heavy-duty applications.
• Provide smooth, consistent operation even under high pressure.
• Well-suited for industrial processes demanding strong, reliable valve control.

Cons:

• Risk of oil leaks, which can cause environmental and safety issues.
• Require more complex maintenance compared to electric or pneumatic actuators due to hydraulic system components.
• Need a hydraulic power unit and clean oil supply, adding to installation and operational costs.

A notable variation is the electro-hydraulic actuator, which blends electric motor control with hydraulic power. This type offers precise positioning with the muscle of hydraulics, often used in subsea systems or where very high reliability is necessary.

For large-scale applications needing maximum force and torque, hydraulic valve actuators remain a top choice despite their maintenance demands, thanks to their robust and powerful operation.

Solenoid Valve Actuators (Direct-acting)

Solenoid valve actuators work on a simple but effective principle: an electromagnetic coil creates a magnetic field when energized, moving a plunger or armature that opens or closes the valve. This direct-acting mechanism is fast and reliable, making solenoid actuators ideal for on/off control.

There are two main types: normally closed (NC) and normally open (NO). In a normally closed valve, the valve stays shut when no power is applied, opening only when energized. The opposite happens with normally open valves—they remain open until power cuts off.

Solenoid actuators are best suited for small 2-way valves where quick cycling is required, such as in fluid control systems, irrigation, or cooling circuits. Their compact size and quick response make them perfect for applications needing rapid and repetitive valve operation. For more details on solenoid valves designed for demanding environments, check out this high-temperature solenoid valve series that offers durability and precise control.

Electro-Hydraulic Actuators

Electro-hydraulic actuators blend the precise control of electric actuators with the powerful force of hydraulic systems. They use an electric motor to drive a hydraulic pump, which then powers hydraulic cylinders or rotary vanes to move the valve. This combination offers excellent accuracy and high torque, making these actuators ideal for heavy-duty applications.

You’ll often find electro-hydraulic actuators used in critical environments like subsea operations and high-integrity pressure protection systems (HIPPS). These sectors demand both precise control and reliable, high-force actuation to handle extreme conditions and ensure process safety.

Because they merge the strengths of electric and hydraulic actuation, electro-hydraulic actuators deliver smooth operation, fast response, and fail-safe capabilities, especially where large valve torque is required but space and power supply are limited.

Manual Valve Actuators: Handwheel, Gearbox, Lever

Manual actuators like handwheels, gearboxes, and levers are the simplest way to operate valves by hand. They don’t rely on any power source, which makes them reliable and easy to use for many applications. You usually find manual actuators on small to medium-sized valves or as a backup option.

When to Choose Manual vs Automated Actuators

• Automation benefits: Remote control, faster response time, integration with control systems, and improved safety for hard-to-reach or hazardous locations.
• Manual override importance: Even with automated valves, manual overrides provide a critical backup in case of power failure, actuator malfunction, or emergency shut-off.

In many industrial setups, it’s common to see manual actuators installed alongside electric or pneumatic actuators to ensure operability under all conditions. This is especially true in environments where precise control is necessary but safety demands a manual fallback.

For reliable valve operation where full automation isn’t practical or cost-effective, manual actuators remain an essential choice for operators across the U.S. industrial sectors.

Smart / Digital Valve Actuators (IoT-Enabled)

Smart or digital valve actuators are the future of automated valve operation, especially as industries move toward more connected, data-driven environments. These actuators come with built-in positioners and advanced diagnostics that continuously monitor valve performance and health. Thanks to wireless technologies like Bluetooth, Wireless HART, or Profibus, operators can get real-time data remotely, improving control accuracy and response times.

One of the biggest benefits is predictive maintenance. By analyzing trends and detecting early signs of wear or failure, smart actuators help avoid unexpected downtime and reduce maintenance costs. This technology also supports partial stroke testing (PST), a critical feature for safety systems to ensure valves partially operate without a full shutdown.

Looking ahead to 2025–2030, smart actuators will play a key role in enabling Industry 4.0 practices, with even greater integration into plant-wide networks and digital twins. Battery-backed designs and low-energy communication standards will make these actuators more reliable and efficient, particularly for remote or hazardous locations. Staying updated on this trend is essential for any plant aiming to improve safety, efficiency, and total cost of ownership.

For more on connected valve automation systems, see solutions designed for power generation and industrial fluids.

Comparison Table: Electric vs Pneumatic vs Hydraulic Valve Actuators

Here’s a quick comparison of electric, pneumatic, and hydraulic valve actuators based on key factors important for most US industrial applications:

Feature	Electric Actuators	Pneumatic Actuators	Hydraulic Actuators
Force/Torque	Moderate to high (depends on motor size)	Moderate (limited by air pressure)	Very high (best for large valves)
Speed	Moderate (seconds to move)	Fast (milliseconds to seconds)	Moderate (depends on system setup)
Precision	High (multi-turn and quarter-turn options)	Moderate (depends on control setup)	Moderate (good but less precise)
Cost (Upfront)	Higher initial cost	Lower initial cost	High (complex system, more equipment)
Maintenance	Low to moderate (electric components)	Moderate (needs clean, dry air)	High (risks of leaks, oil changes)
Safety	Can be explosion-proof, but battery backup needed for fail-safe	Intrinsically safe and fail-safe (spring return)	Generally safe but oil leakage risks
Environment Suitability	Good for indoor/outdoor, requires electrical supply	Best in hazardous areas with proper air supply	Suited for heavy-duty, high-torque, large valves
Power Source	Electricity	Compressed air	Hydraulic fluid pump
Fail-Safe Options	Available with battery backup or external power	Spring return (fail-safe open/close)	Fail-safe with accumulator systems

This table reflects general trends, but specific models and industries may vary. For example, multi-turn electric actuators offer precision for process control, while pneumatic actuators shine in fast-acting, fail-safe applications such as emergency shutdown valves. Hydraulic actuators are preferred for high-torque needs in heavy industrial settings.

For detailed electric actuator solutions, check out the DK60 P-Series motorized ball valve that integrates well with process automation systems.

This comparison will help you weigh your options based on cost, safety requirements, and operational environment when selecting the right valve actuator.

Key Selection Criteria for Valve Actuators

Choosing the right valve actuator comes down to several critical factors:

• Valve type and size: Different actuators suit different valves—quarter-turn actuators work well for ball or butterfly valves, while multi-turn actuators are better for gate or globe valves.
• Torque and thrust requirements: Make sure the actuator can deliver enough force to move the valve under all operating conditions, including pressure and friction. Calculating the required actuator torque accurately is essential to avoid underperformance.
• Power source availability: Is electric power reliable on-site, or is compressed air more accessible? This often dictates if you go electric, pneumatic, or hydraulic.
• Fail-safe needs: Some processes require fail-safe actuators that default to open or closed positions during power loss. Consider if a spring-return pneumatic actuator or battery-backed electric actuator fits your safety protocols.
• Hazardous area classification: For locations with explosion risks, ATEX or IECEx-certified actuators ensure safe operation. Explosion-proof electric actuators or intrinsically safe pneumatic options should be prioritized.
• Speed and duty cycle: High-speed or frequent cycling demands actuators designed for durability and fast response times.
• Environmental conditions: Temperatures can vary from -50 °C to +80 °C, and some sites involve corrosive chemicals or subsea installations. Choose actuators rated for your specific environment.
• Total cost of ownership (TCO): Evaluate installation, maintenance, energy consumption, and longevity. For example, electric actuators may have higher upfront costs but lower maintenance compared to pneumatic or hydraulic systems.

Consider these factors carefully to select an actuator that matches your operational needs while ensuring reliable, efficient valve automation.

For applications needing reliable pneumatic actuators with quick actuation, take a look at the pneumatic UPVC double union ball valve which pairs well with quality pneumatic actuators.

Latest Trends in Valve Actuation (2025)

The valve actuator industry is evolving rapidly, with 2025 bringing some exciting trends that are changing how plants operate. One major shift is the rise of all-electric plants. Battery-backed electric actuators are becoming more common, offering reliable fail-safe operation without needing external air or hydraulic power. This supports greener, more energy-efficient setups while boosting operational uptime.

Industry 4.0 integration is another hot trend. Smart valve actuators now often come equipped with advanced diagnostics and wireless communication like HART or Profibus, enabling real-time monitoring, predictive maintenance, and remote control. Partial stroke testing (PST) is increasingly popular, especially in safety-critical systems, allowing you to check valve function regularly without full shutdowns.

Pneumatic actuators are not left behind. New low-bleed and zero-bleed designs help reduce methane emissions, which is crucial for meeting environmental regulations and improving safety. These eco-friendly improvements allow plants to cut leaks and reduce operational costs, making pneumatic valves more sustainable.

Together, these advances in electric, pneumatic, and smart valve actuation are driving safer, greener, and more efficient process control systems across U.S. industries. For a look at reliable electric options, check out our electric ball valve actuators designed for precise control in automated valve systems.

FAQ About Valve Actuators

What is the most common valve actuator type?

Pneumatic actuators are widely used in many industries due to their simplicity, fast response, and intrinsic safety. However, electric valve actuators are gaining popularity, especially where precise control and integration with digital systems are key.

Electric or pneumatic — which is better?

It depends on your application. Electric actuators offer precise control, are easy to integrate with automation systems, and don’t require air or oil supply. Pneumatic actuators are robust, fast, and fail-safe with spring-return options, but they need clean, dry compressed air and can be less precise.

Can electric actuators be used in explosion-proof areas?

Yes, but only if they are designed and certified as explosion-proof or explosion-resistant (commonly ATEX or IECEx certified). Many electric actuators include explosion-proof enclosures to safely operate in hazardous locations.

What is the difference between scotch-yoke and rack & pinion actuators?Scotch-yoke actuators convert linear motion of a piston into rotary motion using a sliding yoke. They deliver high torque at low speeds and are ideal for quarter-turn valves.
Rack & pinion actuators use a gear rack moved by pistons to rotate a pinion gear which turns the valve stem. They provide smooth and efficient rotary motion, commonly used in pneumatic actuators.How do you calculate the required actuator torque?

To size an actuator correctly, you combine the valve torque requirement (based on valve size, type, pressure, and fluid characteristics) with external factors like seat friction and safety margins. The basic formula is:

Required Torque = Valve Operating Torque × Safety Factor

Manufacturers often provide torque curves and calculation tools to help choose the right actuator size for your valve.

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For more on pneumatic valve solutions, check the detailed range of pneumatic actuated ball valves.