| Manual Actuator | Human effort | Rotary or linear | - Gate valves
- Globe valves
- Ball valves
- Butterfly valves
| A handwheel, lever, or gearbox transfers operator input to the valve stem or shaft. | - Simple construction
- No external power required
- Low installation cost
| - Requires local operation
- Slow for frequent adjustments
- Not suitable for remote control
| Normally remains in its last manually selected position. |
| Pneumatic Actuator | Compressed air or gas | Rotary or linear | - Ball valves
- Butterfly valves
- Globe valves
- Control valves
| Air pressure acts on a piston or diaphragm to produce force and move the valve. Springs may return the valve when air pressure is removed. | - Fast response
- Suitable for hazardous areas when properly configured
- High power-to-weight ratio
| - Requires a clean, reliable air supply
- Air preparation and tubing are needed
- Position accuracy may require additional accessories
| Spring-return designs can be configured to fail open or fail closed when air pressure is lost. |
| Electric Actuator | Electrical power | Rotary or linear | - Ball valves
- Butterfly valves
- Gate valves
- Globe valves
| An electric motor drives a gearbox, screw, or stem mechanism. Limit switches, torque protection, and position sensors control movement. | - Precise positioning
- Easy integration with control systems
- No compressed-air system required
| - Generally slower than pneumatic operation
- Requires electrical protection in hazardous environments
- Motor and gears may need maintenance
| May remain in position, move to a defined position, or use a backup spring or battery system, depending on the design. |
| Hydraulic Actuator | Pressurized hydraulic fluid | Rotary or linear | - Large ball valves
- Large butterfly valves
- Gate valves
- High-force isolation valves
| Hydraulic pressure acts on a piston or vane to create high force or torque for moving the valve. | - Very high force capability
- Good control of large valves
- Suitable for demanding industrial applications
| - Requires a hydraulic power unit or fluid supply
- Fluid leaks can affect reliability and cleanliness
- Installation is more complex
| Spring-return or stored-energy systems can provide fail-open or fail-closed action when hydraulic pressure is lost. |
| Quarter-Turn Actuator | Manual, pneumatic, electric, or hydraulic power | Approximately 90-degree rotation | - Ball valves
- Butterfly valves
- Plug valves
| The actuator rotates the valve shaft through a limited angle to move the closure element between open and closed positions. | - Compact design
- Rapid operation
- Well suited to on/off service
| Not suitable for valves that require multiple turns or long linear stem travel. | Can use a spring-return mechanism or other stored energy to reach a safe position. |
| Multi-Turn Actuator | Manual, electric, or hydraulic power | Multiple rotations | - Gate valves
- Globe valves
- Rising-stem valves
| The actuator rotates the stem or stem nut through several turns, producing linear movement and seating force. | - Suitable for long stem travel
- Can generate substantial thrust
- Supports accurate end-position control
| Usually requires more space and takes longer to operate than quarter-turn equipment. | Fail position depends on the actuator design, valve load, and any installed backup or spring mechanism. |
| Modulating Actuator | Electrical, pneumatic, or hydraulic power with a control signal | Continuous rotary or linear adjustment | - Control valves
- Characterized ball valves
- Butterfly valves
- Globe valves
| A controller compares the desired process value with feedback and adjusts the valve position to regulate flow, pressure, temperature, or level. | - Automatic process regulation
- Remote operation
- Position feedback can improve control accuracy
| - More complex than on/off actuation
- Requires suitable sizing and tuning
- Frequent movement may increase wear
| Often configured to fail open, fail closed, or fail in place according to process safety requirements. |
| On/Off Actuator | Manual, pneumatic, electric, or hydraulic power | Movement between defined end positions | - Isolation valves
- Emergency shutdown valves
- Process diversion valves
| The actuator drives the valve fully open or fully closed in response to a local or remote command. | - Simple control logic
- Reliable isolation
- Suitable for emergency shutdown service
| Does not normally provide precise flow regulation and may cause process shock if operated too quickly. | The selected safe position depends on whether continued flow or stopped flow is safer for the process. |
| Key Selection Factors | Process requirements and available utilities | Quarter-turn or multi-turn; rotary or linear | Valve type, size, pressure rating, and service conditions | Selection involves matching required torque or thrust, operating speed, control method, duty cycle, environmental conditions, and valve travel. | - Improves operational reliability
- Supports safe and efficient valve operation
- Helps prevent undersizing and excessive wear
| Incorrect sizing or unsuitable materials can cause slow operation, incomplete travel, leakage, or premature failure. | Choose the fail position based on the hazards and consequences of loss of power, air, hydraulic pressure, or control signal. |
