Created on 04.24

Pneumatic or electric: what to choose?

Pneumatic or electric: what to choose?

Apr 24, 2026

A pneumatic butterfly valve is a type of actuated butterfly valve. The actuator operates on compressed air, so it can open or close the disc. These valves are also known as pneumatic actuators. 

Not all air-actuated butterfly valves are pneumatic. Understanding the different types will help you choose the right actuator. 

This guide discusses the operating principle of actuated valves, different types of valves, and their operating principles. Various applications and benefits of using actuated valves are also discussed. 

What is an actuated butterfly valve?

A butterfly valve controls flow through a disc that rotates 90 degrees inside a pipe. To open or close the disc, an operator turns a lever or gear to stop or allow flow. In the actuated version, this happens automatically. The power source can be a pneumatic, electric, or hydraulic motor. 

The quarter-turn mechanism makes butterfly valves ideal for industrial applications. Compared to gate valves or ball valves, they open and close faster, weigh less, and take up much less space.

What are the different types of actuated rotary valves?

To understand the principle of operation of a pneumatic actuator, it is necessary to understand the different types of actuated valves and their operating principles:

A pneumatic or valve with a pneumatic actuator operates on compressed air or compressed air.

An electric or valve with an electric actuator operates on electricity.

A hydraulic valve is driven by hydraulics.

What components make up an electric actuated butterfly valve?

An actuated shut-off valve consists of a body, disc, stem, and seal. The components are similar to those of a manual valve; the only difference is the actuator that controls it.

The image below shows the components of a pneumatic valve, which will help you understand its operating principle.

How does a pneumatic rotary actuator work?

A pneumatic rotary actuator's operating principle is based on the use of compressed air, usually at a pressure of 6 to 8 bar. Compressed air drives internal pistons that rotate the valve stem. This provides an opening-closing cycle time of 2 seconds or less, allowing for rapid process isolation.

A pneumatic valve is also called a pneumatic actuator. When choosing this type, you can also select one of two main configurations:

Double acting: Compressed air drives the disc to the open and closed positions. This configuration provides a faster operating cycle and is suitable for high-frequency applications. In this case, speed is more important than the fail-safe position.

Spring return or single-acting: When the air supply is lost, the valve opens under the action of air, and when the air supply is cut off, a mechanical spring closes it. This is ideal for safety-critical systems. When the air supply is interrupted, the valve automatically closes, preventing uncontrolled flow.

Pneumatic or electric: which to choose?

In hazardous or explosive environments classified as ATEX zones, a pneumatic actuator is the only compliant option.

Electric motors generate heat and sparks, posing a risk. Compressed air is safer in oil and gas, chemical, and pharmaceutical industries.

Pneumatic actuators also operate faster than their electric counterparts. This makes them ideal for high-frequency automated processes. They are simpler to operate and do not require complex motor control systems. Additionally, with appropriate IP protection, they can withstand water exposure.

How to choose a pneumatic butterfly valve?

To select a pneumatic butterfly valve, you need to choose the valve and pneumatic actuator according to the process conditions, piping, and control requirements.

Here is a step-by-step guide to selecting a pneumatic valve in case you need to perform... replacement of a pneumatic butterfly valve:

Step 1: Determine your process conditions.

Check the type of working medium, such as water, air, or chemicals. Evaluate the conditions: if the medium is a slurry, corrosive, flammable, etc. This will help you choose suitable materials, such as cast iron, ductile iron, stainless steel, or lined bodies.

Evaluate temperature and pressure. Ensure that the nominal parameters of the valve and seat match your maximum operating temperature and pressure, including pressure surges.

Assess your flow control needs. Do you require simple on/off or partial opening? This will affect the need to select the type of positioner and actuator.

Step 2: Select the appropriate valve size and type.

Select the pipe diameter according to the valve bore diameter (DN/NPS) and the required flow rate/velocity. This will avoid oversizing the diameter and ensure precise regulation.

Choose the body type: wafer, lug, or flanged. This depends on the pipe mounting method and whether the pipeline weight needs to be supported or if the pipeline needs to be removable.

Ensure compatibility of the disc and seat material. For protection against water or air, choose discs with a rubber seal (NR, EPDM, NBR). Discs with a PTFE seal or metal seat are ideal for high temperatures, abrasive conditions, or chemical exposure.

Step 3: Select the pneumatic actuator.

When selecting the actuator type, two processes must be considered. Firstly, a spring-return actuator (fail-safe) closes or opens upon air leakage. It is ideal for safety-critical lines. Secondly, there is a double-acting actuator, which requires air to open and close. It is needed for large valves where more force is required.

Assess the available air pressure in the air supply system (typically 4 to 8 bar). Ensure that the actuator's actuation torque matches the valve's torque at operating pressure. Check the manufacturer's information. Manual pneumatic rotary butterfly valve for torque/pressure diagrams.

Consider the use of auxiliary devices such as solenoid valves, limit switches, positioners, and filter/regulators. These are necessary for control and monitoring.

Step 4: Check installation and environment.

Assess the space and orientation. Ensure there is enough room for the actuator, limit switches, and manual override. Also, check if vertical or horizontal installation is required.

Check the temperature, humidity, and presence of hazardous conditions in the environment. This is crucial for ATEX/IECEx compliant actuators that may pose a risk in explosive atmospheres.

Always check certifications for compliance with standards for the plumbing, heating, ventilation, oil and gas, or chemical industries. Examples of certifications include API, ISO, ANSI, and PN/DN pressure ratings.

Step 5: Determine the control mode and additional devices.

Assess whether you need a simple two-way solenoid valve (on/off only) with spring return. Such valves are often used for ventilation, water supply, or emergency shutdown.

If modulating control is required, add a positioner and a 4-20 mA/pulse signal. This will help proportionally adjust the disc angle to regulate flow.

If you need to monitor operation from a control room, use limit switches or intelligent positioners.

When should you plan to replace a pneumatic rotary butterfly valve?

If a visible external leak is detected in the seat or body area, replace the valve assembly immediately. Other signs include slow response time that persists after actuator maintenance, as well as stem wear or scoring that leads to disc misalignment or corrosion.

Under intensive operation, multiple repairs are more expensive than replacement. Replacement of a pneumatic butterfly valve.

Concentric butterfly valve with resilient seat

Connection form: Wafer, Lug, Flange Nominal diameter: DN50–DN1200 (NPS 2″~48″) Design and production standards: AWWA, ANSI, DIN, JIS, GOST

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Conclusion

A pneumatic butterfly valve is ideal for flow control systems requiring automation. The correct choice of valves helps reduce labor costs, increase process stability, and improve safety. This is especially important in hazardous environments where the use of electric actuators is not recommended.

Regular maintenance and inspection will help identify signs of wear and leaks. As soon as you notice these signs, schedule planned maintenance. Replace the pneumatic butterfly valve immediately. Check the attached manual butterfly valve. Before ordering a replacement, consult the technical specifications.

STARRY Valve manufactures pneumatic butterfly valves that comply with API 609, ASME, and ISO standards. Our technical team will assist you in calculating the specifications that meet the requirements for actuators for your project.