A valve actuator is a vital component in controlling the opening and closing of a valve. Its name says it all: it ensures the valve performs its function accurately. It is a box-like device that provides power to drive the valve stem, opening, closing or regulating the valve. It is the obvious alternative to manual operation and is central to achieving valve automation and remote control.
Definition and Core Functions of a Valve Actuator
Its primary function is straightforward: to receive signals (electrical, pneumatic, or hydraulic) from the control system and convert them into corresponding mechanical displacement or torque. This actuates the valve core, valve disc, or valve stem to open, close, or regulate the valve.
Core Functions
- Automated Control: Replaces manual operation and enables remote control and programmed linkage of valves. Ideal for hazardous operating conditions such as high temperature, high pressure, toxic, and flammable materials.
- Precision Adjustment: With feedback devices (potentiometers, encoders, intelligent positioners), actuators achieve high-precision valve opening control, keeping flow, pressure, and temperature stable.
- Safety Protection: In emergencies (overpressure, power outages, air supply failures), actuators execute safety actions such as rapid closing, opening, or maintaining position to ensure system and personnel safety.
Types of Valve Actuators
By Operation Mode
- Rotary Valve Actuators: Generate rotary motion for valves such as ball, plug, and butterfly valves.
- Linear Valve Actuators: Generate linear motion for valves like globe, gate, and pinch valves.
By Power Mode
Actuators can be classified as fluid power (pneumatic/hydraulic), electric, and manual. Below are their characteristics and applications:
I. Fluid Power Actuators (Pneumatic & Hydraulic)
1. Quarter-turn Actuator
Working Principle: Powered by compressed air or hydraulic oil, converting linear motion into 90° rotation via piston, rack & pinion, or scotch yoke mechanism. Ideal for quick open/close valves (ball, butterfly).
- Pneumatic Advantages: Simple structure, explosion-proof, fast response. Limitations: lower control accuracy, requires air system.
- Hydraulic Advantages: High torque, smooth movement, strong resistance to deviation. Limitations: bulky, requires hydraulic station.
- Applications: Chemical and petroleum industries (e.g. Revo pneumatic actuator).
2. Multi-turn Actuator
Features: Requires multiple rotations (≥360°) to open/close, suitable for linear valves (gate, globe).
- Pneumatic Multi-turn: Scotch yoke or screw mechanism, high thrust but limited precision.
- Hydraulic Multi-turn: Electro-hydraulic servo integration, combining precise control with hydraulic power. Best for high-load conditions (power stations).
II. Electric Actuators
1. Multi-turn Electric Actuator
Working Principle: Motor + worm gear/gear set converts high-speed rotation into low-speed, high-torque output. Closed-loop control via encoder.
- Advantages: Accuracy (±0.02%), supports Modbus, adaptive programmable control.
- Limitations: Frequent motor starts may cause overheating, gear wear. Explosion-proof design required.
- Applications: Process industries requiring precision (power, water treatment).
2. Quarter-turn Electric Actuator
Design: Outputs 90° angular displacement, compact, often integrated with intelligent controllers (e.g. SMARTLINK series).
- Functions: Fault position memory, torque protection, superior positioning compared to pneumatic actuators.
- Applications: Automated ball and plug valves, widely used in building automation, food, and pharmaceutical industries.
III. Manual Valve Actuators
1. Lever
The simplest manual operation, directly driving the stem via a lever. Best for small-diameter, low-pressure valves in emergencies.
2. Handwheel
Provides torque increase via worm gear/gear reduction. Can be standalone or backup for electric/pneumatic actuators.
- Linear Handwheels: For gate valves.
- Quarter-turn Handwheels: For butterfly valves.
3. Manual with Limit Switch
Integrates mechanical or electronic limit switches to stop valves at set positions. This ensures safety by preventing over-travel damage and provides position feedback to control systems.
Comparison Summary
| Power Type | Control Precision | Output Force/Torque | Response Speed | Typical Application Scenarios |
|---|
| Pneumatic Actuator | Medium | Medium – High | Fast | Explosive atmospheres (e.g., chemical plants), quick on/off applications . |
| Hydraulic Actuator | High | Very High | Medium | High-load applications (e.g., power plants, heavy machinery) . |
| Electric Actuator | High – Very High | Medium – High | Slow – Medium | Precision control, remote operation, situations where air/oil supply is impractical . |
| Manual Actuator | Human-dependent | Low – Medium | Slow | Backup operation, small valves, or where automation is not required |
Working Principle of Valve Actuators
Valve actuators with different drive modes are suitable for different operating conditions.
1. Electric Actuator
Working Principle: A motor outputs torque through a gear or worm gear reduction mechanism, driving the valve stem for rotational or linear motion. Closed-loop control is achieved with a control unit and position sensor.
- Performance Features:
- High control accuracy (opening error < ±0.5%).
- Fast response with full stroke time as low as 10 seconds.
- Supports complex adjustment, remote monitoring, and networked control.
- Applications: Power industry (e.g. nuclear plants) with explosion-proof, high-torque actuators (up to 50,000 N·m).
2. Pneumatic Actuator
Working Principle: Compressed air drives a piston or diaphragm, generating linear thrust, converted into linear or rotary motion. Two types: single-acting (spring return) and double-acting (bidirectional).
- Performance Features:
- Excellent explosion-proof performance, safe in hazardous atmospheres.
- Affordable, simple, and reliable.
- Output force proportional to air pressure (e.g. 3000 N thrust at 0.6 MPa).
- Applications: Widely used in chemical and petrochemical industries, ~35% of total pneumatic actuator demand (MarketsandMarkets 2023).
3. Hydraulic Actuator
Working Principle: High-pressure hydraulic oil drives a cylinder, generating massive thrust or torque that directly acts on the valve mechanism.
- Performance Features:
- Extreme torque range (up to meganewtons) for extra-large valves.
- Smooth operation and resistance to external forces, suitable for heavy loads and frequent use.
- Complex system requiring hydraulic stations, high sealing standards, and maintenance.
- Applications: Main valves in hydropower stations, long-distance pipelines, large refining and chemical plants.
| Actuation Method | Subtype / Category | Working Principle | Advantages | Limitations / Notes | Typical Applications |
|---|
| Fluid Power | Quarter-turn (90° type) | Compressed air or hydraulic fluid generates linear force, converted to rotary motion via rack & pinion or Scotch-yoke mechanism | Fast response, simple structure, high output force | Lower precision, complex system (esp. hydraulics) | On/Off valves (ball, butterfly) |
| Multi-turn | Continuous rotation (≥360°) to drive linear valves | Strong output force, suitable for large valves | Limited precision, complex system | Gate valves, globe valves, control valves |
| Electric | Multi-turn | Motor + worm/gear reducer delivers high torque; closed-loop control with encoder | High precision (±0.02%), remote communication, programmable | Heat buildup under frequent starts, gear wear, requires explosion-proof design | Precision control (power plants, water treatment) |
| Quarter-turn | Direct 90° rotary output, compact design, often with integrated intelligent controllers | Accurate positioning, fault memory, torque protection | Higher cost, complex design | Automated ball valves, slide gate valves |
| Manual | Lever | Basic mechanical lever directly moves the stem | Simple, low cost | Manual effort, low efficiency | Small-diameter, low-pressure valves, emergency use |
| Handwheel | Worm/gear reduction increases operator leverage | Easy to operate, backup option | No remote/automation | Linear or rotary valves |
| Manual + Limit Switch | Manual device with mechanical/electronic limit switches | Prevents over-travel, provides position feedback | Added structural complexity | Manual operation with safety/control requirements |
Finally, after reading our article, you will have a better understanding of what valve actuators are, which will help you select valve actuators. Welcome to purchase Raymon valve actuators. Contact us to get the best discounts, give you some options and give you some Valve Actuator Terminology Overview:
How to Choose the Right Valve Actuator
Selecting the right valve actuator is critical for safe, reliable, and efficient operation. Here are the key factors to consider:
| Factor | What to Check | Why It Matters |
|---|
| Power Source | Is electricity, compressed air, or hydraulic power available on site? In hazardous areas, pneumatic is preferred. | Ensures compatibility and safe operation. |
| Output Torque / Thrust | Must exceed the valve’s maximum operating torque by at least 15–20%. | Prevents actuator stalling or mechanical failure. |
| Operation Type | Simple open/close (on-off, 90° rotation) or precise control (0–100% positioning)? | Matches actuator to process requirements. |
| Operating Speed | How fast does the valve need to open/close? | Critical for emergency shutdown or process timing. |
| Control Signals | What signal type is needed—digital on/off, analog (4–20 mA), or fieldbus? | Ensures seamless integration with control system. |
| Environment | Outdoor use, corrosive conditions, explosive atmosphere, temperature extremes. | Protects actuator from harsh environments. |
✅ Tip: Always size actuators with a safety margin. Undersized actuators are the #1 cause of failure.
Valve Actuator Terminology Overview
| No. | Term | Definition & Features | Typical Applications |
|---|
| 1 | Pneumatic Actuator | Powered by compressed air; simple structure, fast action, explosion-proof, high thrust, easy maintenance. | Chemical, paper, refining industries |
| 2 | Electric Actuator | Powered by electricity; high precision, quick response, supports remote and smart control. | Power plants, automation systems, building control |
| 3 | Hydraulic Actuator | Powered by pressurized fluid; delivers very high thrust/torque, suitable for heavy-duty use. | Heavy machinery, shipbuilding, hydropower |
| 4 | Electro-Hydraulic Actuator | Combines electric signals with hydraulic drive; merges accuracy with high force. | Energy, high-end equipment, harsh conditions |
| 5 | Actuator Power Unit | Core driving component; converts air, electric, or fluid energy into mechanical motion. | All actuator types |
| 6 | Actuator Stem | Linear motion part; transfers thrust to move the valve plug. | Linear control valves |
| 7 | Actuator Shaft | Rotary motion part; transfers torque to drive valve rotation. | Ball valves, butterfly valves |
| 8 | Yoke | Rigid connection between actuator and valve; provides stability and vibration reduction. | Various valve systems |
| 9 | End Connection | Valve body connection to pipeline; determines sealing and installation method. | Industrial piping systems |
| 10 | Flange Ends | Bolted flange connection; reliable sealing, easy maintenance. | High-pressure piping, petrochemical |
| 11 | Flangeless Ends | Clamped between flanges; compact design, space-saving. | High-temp, high-pressure, corrosive media |
| 12 | Threaded Ends | Threaded connection; low cost, simple, for low-pressure use. | Domestic, low-pressure systems |
| 13 | Welded Ends | Welded connection; robust, excellent sealing, suitable for extreme conditions. | High-pressure steam, long-distance pipelines |
Summary
Valve actuators are the core driving device for valve automation, precise control and safe operation. It is vital to consider operating conditions, power sources and control accuracy requirements. The key to success is balancing the power source (electric/pneumatic/hydraulic/manual) with the motion mode (multi-turn/quarter-turn). Actuator technology is evolving towards intelligence, integration and high reliability, providing even stronger support for industrial automation systems.
Key selection factors include the available power source (electric, pneumatic, hydraulic), required output torque/thrust, operation type (on/off/modulating), speed requirements, control signal, and operating environment conditions.
