How to Select an Electric Actuator: A Step-by-Step Guide
Selecting the right electric actuator is crucial for the efficiency, safety, and reliability of your automated system. An incorrect choice can lead to premature failure, poor performance, or even safety hazards. This guide outlines the key factors to consider when choosing an electric actuator for your application.
1. Determine the Type of Motion: Quarter-Turn vs. Multi-Turn
The first step is to match the actuator to your valve or device.
Quarter-Turn Actuators: Used for valves that require a 90-degree rotation to open or close, such as ball, butterfly, and plug valves.
Multi-Turn Actuators: Used for valves that require multiple rotations to open/close, such as gate and globe valves.
Linear Actuators: Provide straight-line push/pull motion for devices like dampers, slides, or knife gate valves.
2. Verify Torque/Force Requirements
This is the most critical technical specification.
For quarter-turn actuators, you need the required torque (in lb-in or Nm). Always select an actuator with a torque output 20-25% higher than your valve's requirement to account for friction, wear, and unexpected load variations.
For multi-turn and linear actuators, you need the required thrust (in lbs or kN).
3. Define Operational and Control Requirements
Voltage & Power Supply: Common options include 24V DC, 120V AC, or 240V AC. Ensure your site can provide the required power.
Control Signal: How will you operate it? For modulating control, a 4-20 mA or 0-10 V signal is standard. For simple on/off control, discrete contacts are sufficient.
Speed (Travel Time): How fast does the valve need to open or close? Actuator speed is measured in seconds per 90° or seconds per inch of travel.
4. Assess the Operating Environment
The actuator must be built to survive its surroundings.
Ingression Protection (IP Rating/NEMA Rating): For outdoor or damp environments, a high IP rating like IP67 is essential for protection against dust and water immersion. In hazardous areas with flammable gases or dust, you must select an actuator with the appropriate ATEX or IECEx explosion-proof certification.
5. Consider Safety & Fail-Safe Features
What must the actuator do in case of a power failure?
Fail-Safe (Spring-Return): Automatically returns to a pre-defined safe position (open or closed) upon power loss.
Non-Fail-Safe (Electric Brake): Stays in its last position when power is cut.
By systematically evaluating these five areas-motion type, torque, control, environment, and safety-you can confidently select an electric actuator that ensures optimal performance and long service life for your specific application. Always consult with valve and actuator manufacturers for precise technical specifications.