Actuators generally include three types: pneumatic actuators, electric actuators, and hydraulic actuators. The broadest definition of an actuator is: a driving device that can provide linear or rotary motion, using driving energy and under the action of control signals to automatically operate some equipment and devices, control their switching and adjustment, and replace manual work. The execution unit is the terminal control unit in the process control industry, usually composed of valves and actuators. This article mainly discusses the differences, advantages and disadvantages between electric actuators and pneumatic actuators. It takes 5 major aspects and 20 points to help you understand the differences between the two.
This article comes from "Valve matching, choose electric actuator or pneumatic actuator, analyze it for you from 20 points! 》
?1) Driving energy 1.1 Ease of obtaining driving source Electric actuator: The driving source is power supply, whether it is three-phase power supply or single-phase power supply, it is very easy to obtain at industrial sites. Pneumatic actuator: The driving source is the air source, which requires a special air source station and pipeline laying. The construction is more cumbersome and increases the budget. The air source is generally compressed air, so it must be equipped with a large air compressor. DeRui Automation Comment: Power supply is easy to obtain at various types of industrial sites. It is more convenient to use electric solutions for actuators of some small equipment (usually small equipment does not have compressed gas, such as plate presses, shield machines, etc.) 1.2 Requirements for driving sources Electric actuators: power supply voltage within a certain range The motor can work normally during fluctuations. The general fluctuation range is ±10% of the rated voltage. Pneumatic actuator: the air source must not contain oil, water, or impurities. Unclean gas will affect the normal operation and life of the actuator and valve positioner. DeRui Automation Comment: Power supply makes it easier to ensure power supply quality. The gas source requires a gas filtering device, which requires more maintenance and testing work, but now most factories will have a gas source.
1.3 Energy saving Electric actuator: Only when changing the opening of the control valve, the motor needs to be driven. When the required opening is reached, the motor is powered off. In standby mode, only a small amount of power is needed to maintain the operation of the control unit.
Pneumatic actuator: A certain air pressure is required during the entire control valve operation and standby state. When the air pressure drops, the compressor will run to increase pressure. DeRui Automation Comment: Generally speaking, electric actuators are more energy-saving than pneumatic actuators.
?2) Application scope
2.1 Action mode Electric actuator: flexible configuration, action modes include: straight stroke, angular stroke, multi-turn. Can be used to control all types of valves. Pneumatic actuators: usually only have two types: straight stroke and angle stroke. They are usually used to control straight stroke regulating valves, butterfly valves, ball valves, etc. Generally, they cannot control gate valves, globe valves and other valves. DeRui Automation Comment: Electric actuators can easily realize multi-turn actions, and their structural forms are relatively flexible. They are especially used to control gate valves, globe valves and other valves that are widely used in industrial sites. Pneumatic actuators generally cannot control the above valves. 2.2 High torque angle stroke valve control Electric actuator: It can achieve a maximum torque of hundreds of thousands of Nm, and the combination is flexible, the volume is relatively small, and it is easy to implement.
Pneumatic actuator: It can also achieve tens of thousands of Nm of torque, but the volume will be very large and inconvenient to install and use. DeRui Automation Comment: For 90° rotary valves with larger torques (more than 10,000 Nm), it is usually more appropriate to use electric actuators. 2.3 Explosion-proof situations Electric actuators: Electrical and electronic components such as motors and control units may generate sparks when in fault conditions, and require special explosion-proof treatment before they can be used in flammable and explosive situations.
Pneumatic actuator: The driving energy is a gas source (air or inert gas), there are no high-voltage and strong electric components, it is not easy to generate sparks, and it has high safety performance. Derui Automation Comment: Some main equipment in petrochemical, metallurgy, coal chemical and other industries often contain flammable and explosive media such as oil, natural gas, and coal gas. For safety reasons, pneumatic actuators are usually used.
Explosionproof electric actuators are usually used in oil depots, tank farms, oil and gas pipelines, gas pipelines and other places where it is inconvenient to lay gas lines. 3) Product performance
3.1 High-temperature-resistant electric actuator: Even if the controller is installed separately, the normal operation of components such as motors and sensors in the main transmission structure is limited by the ambient temperature, and the ambient temperature resistance is average. Not exceeding 80℃. Pneumatic actuator: After the valve positioner is installed separately, the main body (cylinder) can be selected as a high-temperature resistant product, which can withstand high ambient temperatures up to 100°C or higher. DeRui Automation Comment: The working environment temperatures of intelligent integrated electric and pneumatic actuators are almost the same. However, after the control unit and the main body are installed separately, the pneumatic actuator is more resistant to high temperatures than the electric actuator. 3.2 Anti-seismic performance
Electric actuator: It is composed of a large number of mechanical and electronic components, and its normal operation and life are greatly affected by vibration. Pneumatic actuator: The overall structure is simple, there are few movable parts, and it is not sensitive to vibration. DeRui Automation Comment: Pneumatic actuators are more resistant to shocks. 3.3 Operating speed Electric actuator: After deceleration through different types of gearboxes, different models of products have different output speeds, and the operating speed is generally not adjustable. Pneumatic actuator: The air source signal is used to adjust the operating speed according to the usage requirements, and can achieve faster operating speeds. DeRui Automation Comment: The pneumatic actuator can achieve fast action response, and the speed is adjustable, improving the adjustment efficiency. Electric actuators require special motors and variable speed control modules to achieve variable speed operation. 3.4 Overload capacity and lifespan
Electric actuator: When the motor moves frequently or is overloaded beyond the usage conditions, it is easy to generate heat, resulting in thermal protection and shutdown midway. Long-term heavy load will also increase the wear of the transmission gear. . Pneumatic actuator: adapts to frequent full-load actions and has long operating life. The valve may increase the starting torque due to medium deposition. Using pneumatic components can increase the working pressure and force within a certain range. DeRui Automation Comment: Pneumatic actuators are more adaptable to frequent and large-load adjustment actions. Adjustable pneumatic actuators have a longer service life, up to 2 million actions. The operating cycle of the regulating electric actuator can reach up to 1.8 million operations.