How To Select An Electric Actuator For a Butterfly Valve

Step 1: Define the Required Valve Function

Before selecting an actuator, first determine how the butterfly valve will be used in the pipeline system. There are two main types of applications: on/off control and modulating control.

On/Off Control

If the butterfly valve is mainly used to open, close, or isolate a pipeline, an on/off electric actuator is the right choice.

When the actuator receives an open or close command, it drives the valve stem and disc to the fully open or fully closed position. Limit switches then send feedback signals to the control system to indicate the valve position.

Some on/off actuators can stop the valve at an intermediate position, but they are not designed for frequent or continuous flow adjustment.

Modulating Control

If the butterfly valve needs to adjust its opening continuously to control flow, pressure, temperature, or liquid level, a modulating electric actuator is required.

This type of actuator typically receives proportional control signals, such as 4–20 mA or 0–10 V, and moves the valve disc to the required opening position. It also provides continuous position feedback to the control system.

Modulating actuators usually operate more frequently than on/off actuators. When selecting one, check its duty rating, positioning accuracy, feedback signal, and motor thermal protection.

For a more detailed explanation of these two control methods, see our guide to the differences between on/off and modulating butterfly valves.

Step 2 — Confirm the Butterfly Valve and Operating Conditions

After defining the control requirements, check the butterfly valve configuration, actual operating conditions, and mounting interface. These details affect the valve operating torque and determine whether the actuator can be properly installed.

Butterfly Valve Specifications

Confirm the following:

• Nominal size and pressure rating
• Valve design: concentric, double eccentric, or triple eccentric
• Seat material
• Operating torque provided by the valve manufacturer
• Differential pressure and temperature conditions under which the torque data applies
• Operating Conditions

Also check:

• Pipeline medium
• Operating temperature
• Normal operating pressure and maximum differential pressure
• Medium viscosity
• Whether the medium contains impurities or is likely to cause deposits or scaling

Mounting Interface

Check the following dimensions and requirements:

• ISO 5211 mounting flange
• Stem shape and dimensions
• Actuator output bore
• Whether a stem adapter or mounting bracket is required
• Actuator rotation direction

Even if both the butterfly valve and actuator comply with ISO 5211, you still need to check that the flange dimensions, stem, and output bore are compatible.

For more details, see our ISO 5211 Butterfly Valve Actuator Selection Guide.

Butterfly valves of the same size may require different operating torques depending on their design, seat material, differential pressure, temperature, and medium. Therefore, actuator selection should never be based on valve size alone.

Step 3 — Determine the Required Actuator Torque

After confirming the butterfly valve specifications and operating conditions, select the actuator based on the maximum torque required to operate the valve throughout its opening and closing cycle.

A basic calculation is:

Required Actuator Output Torque = Maximum Valve Operating Torque × Safety Factor

Always use the torque data provided by the valve manufacturer whenever possible. During preliminary selection, an additional safety margin is usually applied to account for changes in seat friction, temperature effects, medium deposits, and increased operating resistance over time.

A safety factor of 1.2–1.5 is commonly used as a reference range. However, the final value should be determined based on the actual valve data and project requirements.

For more information about breakaway torque, running torque, safety factors, and detailed calculation methods, see our Butterfly Valve Actuator Torque Selection Guide.

Step 4 — Select the Electrical and Control Configuration

After confirming the actuator type and required torque, determine the electrical configuration based on the available power supply and control system at the installation site.

Power Supply Requirements

Common actuator power supply options include DC 24 V, AC 110 V, AC 220 V, and AC 380 V. In addition to voltage, confirm the following:

• AC or DC power supply
• Single-phase or three-phase
• 50 Hz or 60 Hz frequency
• Allowable voltage fluctuation range

The actuator voltage, phase, and frequency must match the available power supply at the installation site. Different actuator models may support different power options, so always check the manufacturer's technical specifications.

Control and Feedback Signals

On/off actuators typically receive open and close commands and send feedback signals to the control system to indicate the fully open or fully closed position.

Modulating actuators typically receive proportional signals such as 4–20 mA or 0–10 V. They adjust the valve opening according to the control signal and provide continuous valve position feedback.

Internal Components of a Modulating Electric Actuator

If the actuator needs to connect to a PLC, BMS, or DCS, also check that the signal types, wiring connections, and communication protocols are compatible.

Local and Remote Operation

Based on the operation and maintenance requirements, determine whether the actuator needs the following functions:

• Local and remote control selection
• Local open, close, and stop controls
• Valve position and fault status display
• Non-intrusive commissioning
• Remote fault alarms
• Fieldbus communication

These requirements should be clearly specified during the inquiry and selection stages. Otherwise, even if the actuator has the correct torque and power supply specifications, it may not work properly with the site's control system.

Step 5 — Confirm the Installation Environment

The actuator's protection rating should be selected based on the site's exposure to rain, dust, humidity, condensation, standing water, and corrosive substances. The IP rating indicates the enclosure's protection against dust and water. It does not replace separate requirements for corrosion protection, condensation prevention, or explosion protection.

Other Important Considerations

• Cable entries and connections: Cable glands, sealing plugs, and field wiring must meet the required protection rating. Otherwise, the actuator enclosure may not maintain its specified IP protection.
• Condensation prevention: Moisture inside the actuator is another major risk in humid environments. Even without water entering the enclosure, temperature changes can cause internal condensation. An anti-condensation heater may therefore be necessary.
• IP68 immersion limits: The immersion conditions for IP68 are specified by the manufacturer. Check the permitted water depth, immersion duration, and cable gland protection. IP68 does not automatically mean the actuator can operate underwater continuously.
• Corrosion and explosion protection: A higher IP rating does not mean better corrosion resistance or explosion protection. For corrosive environments, check the enclosure material and protective coating separately. For hazardous areas, confirm the explosion protection rating, temperature class, and whether the certificate covers the selected actuator model.

Step 6 — Determine Feedback and Fail-Safe Requirements

During actuator selection, determine what the butterfly valve should do if the control signal or power supply is interrupted. Should it close, open, or remain in its current position?

Consider the following three situations:

• Control Signal Loss: For modulating actuators, confirm the preset action when the control signal is lost: remain in the current position, move to fully open, or move to fully closed.
• Power Failure: Standard electric actuators typically stop operating and remain in their current position when power is lost. If automatic opening or closing is required, a spring-return actuator, energy storage device, or backup power supply may be needed.
• Emergency Shutdown: If the system includes an Emergency Shutdown (ESD) function, specify the required valve position when an emergency signal is triggered. Also, confirm whether the ESD command must override all other control commands.

Based on the process and safety requirements, determine the required fail-safe action:

• Fail Close (FC)
• Fail Open (FO)
• Fail in Place (FIP)

Fail-safe requirements should be clearly specified during the inquiry and actuator selection stages. Do not assume that the actuator's standard configuration will meet the required safety function.

Get Technical Drawings and a Project Quotation

Selecting an electric actuator for a butterfly valve involves more than checking the actuator specifications. The valve torque, mounting interface, and control requirements must also be compatible. Checking these details in advance helps avoid installation and commissioning problems and ensures reliable valve operation under the specified conditions.

With over 20 years of valve manufacturing experience, UNION VALVE offers electric butterfly valves in various sizes and configurations. We support different body, disc, and seat materials, along with a range of actuator options for water supply, wastewater treatment, HVAC, and industrial pipeline applications.

If you are sourcing electric butterfly valves for a project, send us your valve size, pressure rating, medium, operating conditions, and control requirements. Our team can help verify the valve and actuator configuration and provide technical drawings, specifications, and a project quotation.

Related Articles:

• SO 5211 Butterfly Valve Actuator Mounting and Selection Guide
• How to Choose Between On Off and Modulating Butterfly Valves
• Butterfly Valve Actuator Sizing: Torque & Selection Guide
• Limit Switch Butterfly Valve: Working Principle and Selection
• Pneumatic Butterfly Valve Basics: What It Is and How It Works