Introduction
Selecting the correct electric actuator is not only about knowing the valve size. A reliable actuator selection depends on several technical factors, including valve type, torque requirement, operating conditions, control requirements, and environmental conditions.
Providing the correct information at the beginning of a project helps avoid delays, incorrect selections, unnecessary costs, and operational problems.
At KVC Africa, we assist clients with actuator sizing and selection to ensure the correct actuator is specified for each application.
1. Valve Type
The first step is identifying the type of valve to be automated.
Common valve types include:
- Butterfly valves
- Ball valves
- Gate valves
- Globe valves
- Plug valves
- Knife gate valves
- Dampers
Different valves require different actuator types. For example, butterfly and ball valves usually require quarter-turn actuators, while gate and globe valves normally require multi-turn or linear actuator solutions.
2. Valve Size
Valve size is important, but it should never be used as the only selection factor.
Two valves of the same size can have very different torque requirements depending on design, pressure rating, seat material, valve condition, and operating pressure.
3. Required Torque or Thrust
Torque or thrust is one of the most important pieces of information needed for actuator selection.
For quarter-turn valves, torque is required.
For multi-turn or linear applications, thrust or stem details may also be required.
Where possible, the valve manufacturer’s torque figures should be supplied. If these are not available, KVC Africa can assist in assessing the application and determining a suitable actuator selection.
4. Operating Pressure and Differential Pressure
The pressure conditions of the system can significantly affect the force required to operate a valve.
Important information includes:
- Line pressure
- Differential pressure across the valve
- Maximum operating pressure
- Start-up or abnormal operating conditions
The actuator must be capable of operating the valve under the most demanding expected conditions.
5. Media Being Controlled
The type of media passing through the valve can also influence actuator selection.
Examples include:
- Clean water
- Wastewater
- Slurry
- Chemicals
- Air
- Steam
- Process fluids
Media characteristics can affect valve friction, corrosion, deposits, scaling, and long-term operating torque.
6. Power Supply
Electric actuators are available in different voltage configurations.
Common options include:
- 230V AC
- 400V AC three-phase
- 24V DC
- Other project-specific voltages
Confirming the available power supply is essential before selecting the actuator.
7. Control Requirements
Different applications require different control methods.
Typical control options include:
- Open-close control
- Local control
- Remote control
- Modulating control
- Position feedback
- Torque feedback
- Fault indication
- PLC or SCADA integration
For modulating applications, it is important to confirm the control signal, such as 4–20 mA or 0–10 V.
8. Communication Requirements
Modern actuators can be integrated into plant communication systems.
Possible communication options may include:
- Modbus
- Profibus
- Ethernet-based communication
- Hardwired control signals
The control philosophy should be confirmed during the selection process.
9. Environmental Conditions
The installation environment affects actuator specification.
Important conditions include:
- Indoor or outdoor installation
- Ambient temperature
- Dust exposure
- Water exposure
- Corrosive atmosphere
- Vibration
- Hazardous area requirements
- IP protection rating
Selecting the correct enclosure and protection level is critical for long-term reliability.
10. Operating Frequency
Actuators used for occasional open-close operation have different requirements from actuators used for frequent cycling or modulating duty.
High-cycle applications require careful attention to duty rating, motor performance, heat generation, and expected operating life.
Conclusion
Correct actuator selection depends on a complete understanding of the valve, process, site conditions, and control requirements.
By providing the right technical information upfront, customers can avoid incorrect selections and improve long-term reliability.
KVC Africa offers actuator sizing, selection, site surveys, supply, commissioning, and technical support for industrial electric actuator applications across South Africa.
If you need assistance selecting the correct electric actuator, contact KVC Africa for expert support.
