What Is an Actuator?

An actuator is a drive device that converts the energy or control signal it receives into mechanical motion and transfers this motion to the equipment to which it is connected.

In valve automation, an actuator enables a valve that would otherwise need to be manually turned or operated to open and close automatically. In quarter-turn valves such as ball valves and butterfly valves, actuators generally produce rotational motion.

With an actuator system, a valve can:

• Be controlled remotely.
• Open and close automatically.
• Be connected to an automation system.
• Be maintained at a specific position.
• Contribute to the control of process pressure, flow rate, or temperature.

What Is a Pneumatic Actuator?

A pneumatic actuator  is a type of actuator that converts compressed air into mechanical motion.

The compressed air supplied to the actuator generates force on a piston or similar mechanism, allowing the valve to move. Pneumatic actuators are particularly preferred in applications where fast opening and closing operations are required.

Pneumatic actuators are generally used in two different configurations:

Single-Acting Pneumatic Actuator

In single-acting models, movement in one direction is provided by compressed air, while movement in the opposite direction is provided by a spring.

This design can allow the valve to return to a predetermined safe position in the event of a loss of energy or air supply. This feature can be important for process safety.

Double-Acting Pneumatic Actuator

In a double-acting actuator, both opening and closing movements are performed using compressed air.

Therefore, the system requires an appropriate and continuous compressed-air supply to operate.

What Is an Electric Actuator?

An electric actuator is a motorized drive system that converts electrical energy into mechanical motion.

Through an electric motor and mechanical transmission components, the required movement is transferred to the valve stem or valve body. Electric actuators can offer advantages in applications where precise positioning and electrical control are important.

One of the key advantages of electric actuators is that, unlike pneumatic systems, they do not require a compressed-air line or compressor infrastructure.

Key Differences Between Pneumatic and Electric Actuators

Because of these characteristics, pneumatic systems can be advantageous for fast and repetitive movements, while electric systems can be more suitable for applications requiring precise and flexible control.

1. Operating Speed

One of the key advantages of pneumatic actuators is their ability to move quickly. They are particularly useful in applications where the valve only needs to be moved to the fully open or fully closed position.

With electric actuators, operating speed depends on the motor, gear system, and actuator design.

Therefore, pneumatic actuators can be advantageous in processes where fast cycle times are important.

2. Control Accuracy

One of the areas where electric actuators stand out is positioning accuracy.

If the valve needs to operate at a specific opening percentage rather than simply being fully open or fully closed, an electric actuator can be a suitable solution.

Position control is also possible with pneumatic systems; however, additional control equipment may be required depending on the level of precision required by the application. Electric systems can offer greater flexibility in motion and position control.

3. Compressed-Air Infrastructure

One of the most significant differences between the two systems is their energy infrastructure.

When using a pneumatic actuator, the system may include equipment such as:

• Compressor
• Air receiver tank
• Air filter
• Regulator
• Air distribution line

Electric actuators, on the other hand, primarily require a suitable electrical power supply.

Therefore, pneumatic systems may be more advantageous in facilities that already have a robust compressed-air infrastructure. In applications where compressed-air infrastructure is unavailable but electricity is readily accessible, an electric actuator may be preferred.

4. Energy Consumption

Energy consumption should not be evaluated based solely on the actuator itself.

In pneumatic systems, the energy consumption of the compressor used to generate compressed air must also be taken into account.

In electric actuators, energy is supplied directly to the electric motor.

Therefore, when selecting an actuator, it is important to consider not only the initial purchase cost but also the actuator's operating frequency, operating time, auxiliary equipment, and total operating cost.

5. Return to a Safe Position

In some processes, keeping the valve in its current position when power or a control signal is lost is not sufficient. The valve may need to automatically move to a safe open or closed position.

Spring-return pneumatic actuators can provide an important advantage in such applications. If the air supply is interrupted, the spring mechanism can move the valve to a predetermined position.

With electric actuators, additional solutions may be required to move the valve to a safe position in the event of a power failure, depending on the actuator's design and features.

6. Maintenance Requirements

In pneumatic systems, the quality of the compressed air is also important. Moisture, contaminants, or unsuitable pressure levels in the air line can affect system performance.

In electric actuators, electrical connections, the motor, gear mechanism, and mechanical components of the actuator should be inspected.

Therefore, there is no universal answer to the question of which system is easier to maintain. The answer depends on the overall system and operating conditions.

Advantages of Pneumatic Actuators

The key advantages of pneumatic actuators include:

• Fast opening and closing
• Simple and robust mechanical construction
• Suitability for repetitive movements
• Ability to return to a safe position with spring-return models
• Easy integration in facilities with compressed-air infrastructure
• Suitability for demanding industrial applications

Pneumatic technology is particularly well suited to automation applications where fast cycle times and durability are important.

Advantages of Electric Actuators

The main advantages of electric actuators include:

• Precise positioning
• Flexible control
• Easy integration with electrical infrastructure
• No need for a compressed-air system
• Models capable of providing valve position feedback
• Easy integration with automation systems

Electric actuators can be particularly advantageous in applications where variable motion profiles and precise position control are important.

Pneumatic Actuator or Electric Actuator?

Rather than giving a single answer to this question, the choice should be evaluated according to the application.

A pneumatic actuator may be preferred when:

• The valve needs to open and close quickly.
• The facility already has a compressed-air infrastructure.
• A high number of repetitive opening and closing cycles is required.
• Returning to a safe position is important.
• A robust and fast solution is required for an industrial environment.

An electric actuator may be preferred when:

• Precise positioning is required.
• There is no compressed-air infrastructure.
• Electrical power is more readily accessible.
• Precise control of the valve position is required.
• Flexible control through an automation system is desired.

What Should Be Considered When Selecting an Actuator?

Choosing the right actuator involves more than simply deciding between a pneumatic or electric solution. The following criteria should be evaluated together:

• Valve type and size
• Required torque
• Operating pressure
• Fluid characteristics
• Operating temperature
• Opening and closing time
• Daily operating cycle
• Need for On/Off or modulating control
• Available energy infrastructure
• Required valve position in the event of a power or air supply failure
• Environmental conditions
• Maintenance and operating costs

In particular, it is critical to ensure that the actuator's torque capacity is compatible with the valve's requirements. The actuator should not merely have enough capacity to move the valve; it should be appropriately sized to ensure safe operation under actual operating conditions.

Conclusion

Pneumatic and electric actuators are not simply direct alternatives to one another. They are two different valve automation solutions designed to meet different requirements.

Pneumatic actuators offer advantages in applications where fast, repetitive, and durable movement is important, while electric actuators stand out in systems requiring precise positioning, flexible control, and electrical infrastructure.

Therefore, when selecting the right actuator, it is important to consider not only the product price but also the valve type, torque requirements, operating frequency, control method, energy infrastructure, safety requirements, and total operating cost.

In short: If speed and simplicity are the priorities, a pneumatic actuator may be the better choice; if precision and control flexibility are the priorities, an electric actuator may be more suitable.

Frequently Asked Questions

Is a pneumatic actuator faster than an electric actuator?

In general, pneumatic actuators have an advantage in fast opening and closing applications. However, actual operating speed depends on the actuator model, valve type, and system conditions.

Does an electric actuator require a compressor?

No. Electric actuators operate using electrical energy and do not require the compressed-air infrastructure used by pneumatic systems.

Do pneumatic actuators use no electricity at all?

The actuator's operating energy is supplied by compressed air. However, electrical power may be used by auxiliary components such as solenoid valves, positioners, or control systems.

Which type of actuator is more precise?

Electric actuators generally offer advantages in terms of precise positioning and flexible motion control.