Optimizing Electric Valves Actuators

Overview

Valve electric actuators (referred to as "electric actuators" hereafter) are specialized transmission devices used to drive valve opening and closing. They consist of specialized motors, worm gears, torque detection mechanisms, and control components.

Electric actuators offer high starting torque and precise valve travel control, making them widely applicable in industries such as petroleum, chemical, hydropower, metallurgy, shipbuilding, light industry, and food processing. Different industries and working conditions have varied requirements for electric actuators, including applications that require handling higher pressures and higher flows.

Classification

Electric actuators are generally classified based on structure type, operation mode, rotation mode, and working environment.

Structure Type

• Integrated Type: All control components are installed inside the actuator, forming a single unit. This type is further divided into ordinary and intelligent types.
• Split Type: Control components are installed in a separate electric control cabinet.

Operation Mode

• Switch Type: Typically, the motor starts less than 600 times per minute. This type is suitable for one-time valve opening or closing.
• Regulation Type: The motor frequently starts, reaching up to 1200 times per minute. It can accept and feedback 4-20mA analog signals, meeting closed-loop control requirements.

Rotation Mode

• Multi-turn Type: Requires multiple rotations to open or close the valve, needing a secondary transmission mechanism.
• Part-turn Type: Requires a 90-degree rotation to open or close the valve, directly connecting to the valve.

Working Environment

• Explosion-proof Type: Designed for flammable and explosive environments.
• Ordinary Type: Suitable for any environment except flammable and explosive conditions.

Selection

The selected electric actuator must meet working conditions, valve switching torque, time (speed), and control requirements. It must be capable of handling various types of valves, such as electric actuated ball valves and solenoid valves.

Ambient Temperature

Electric actuators are enclosed, leading to poor heat dissipation. Using actuators outside their temperature range can affect insulation, output torque, and lifespan. Ensure the temperature range is appropriate for high-temperature environments.

Protection Level

Protection levels, indicated by "IP" followed by two digits, measure dust and water resistance. Indoor environments typically use IP54 or IP55, while outdoor environments use IP55 or IP65. In dusty conditions, higher protection levels like IP65 or IP67 are needed. For immersion in water, use IP67 or IP68, with IP68 indicating submersion at 3m depth for 72 hours without water ingress.

Control Type

Refers to whether the actuator is integrated or split. Intelligent integrated actuators are commonly used, featuring LCD display, electronic position and torque sensors, valve position feedback (4-20mA), auto phase correction, reverse protection, jam protection, data recording, auto diagnosis, and optional field bus communication. Selection depends on working conditions and budget.

Torque

Calculate the maximum torque required for valve operation before selecting the actuator. Actuators have torque protection; an oversized torque can damage the valve if obstructions occur before the protection activates.

Speed

Output speed affects valve operation time. Some conditions specify valve operation time, necessitating appropriate speed selection. Even if not specified, actuator motors operate in short cycles, typically no more than 10-15 minutes. Speed and torque must match.

Control Requirements

Control requirements depend on whether the actuator is for regulation or switching. Regulation actuators frequently start and handle 4-20mA signals for closed-loop control. Switching actuators only control valve opening/closing, with limited continuous operation time. Additional requirements may include valve status feedback to control rooms and control methods. When dealing with stainless steel ball valves, it is essential to ensure compatibility with the actuator's capabilities to handle higher pressures.

Conclusion

To ensure the reliability and durability of valve actuators, selection should consider installation position, usage requirements, pressure, diameter, cost-performance ratio, and protection level. Proper selection is crucial, whether for handling higher flows or ensuring the actuator efficiently closes the valve to maintain the desired flow path.

FAQs

1. What are the main components of an electric actuator?
   • Electric actuators consist of specialized motors, worm gears, torque detection mechanisms, and control components.
2. How are electric actuators classified based on structure?
   • They are classified into integrated and split types.
3. What is the significance of IP protection levels in actuators?
   • IP levels indicate the degree of protection against dust and water.
4. Why is torque calculation important in selecting an electric actuator?
   • Proper torque calculation ensures the actuator can handle the valve's operational requirements without damage.
5. What factors influence the choice between regulation and switching actuators?
   • Factors include operation frequency, signal handling capabilities, and specific control requirements.