Introduction to Basic Types of Pneumatic Actuators
On this page
Pneumatic actuators are devices that utilize air pressure to drive the opening and closing or adjustment of control valves, also known as pneumatic actuating mechanisms or pneumatic devices, commonly referred to as pneumatic heads. They play a crucial role in industrial automation, enabling precise control of control valves. The core functions of pneumatic actuators include the opening and closing and adjustment of valves, with the actuating mechanisms mainly divided into three types: diaphragm, piston, and rack-and-pinion.
Diaphragm Actuators
Diaphragm actuators are the most common type of pneumatic actuator, widely used in various control valve drive systems. They utilize pneumatic pressure to drive the deformation of the diaphragm, thereby achieving precise control of the valve.
1. Working Principle
The core component of the diaphragm actuator is a diaphragm. When pneumatic signal pressure is applied to the diaphragm, it deforms. The push rod on the diaphragm moves with the deformation of the diaphragm, pushing the valve core to displace and thus changing the valve opening. The specific process is as follows:
Signal pressure application: Pneumatic signal pressure is applied to one side of the diaphragm.
Diaphragm deformation: The diaphragm deforms under the pressure.
Push rod movement: The deformation of the diaphragm moves the push rod.
Valve core displacement: The movement of the push rod causes the valve core to displace, adjusting the valve opening.
2. Main Advantages
Diaphragm actuators have the following advantages:
Simple structure: The design and manufacturing process is relatively simple, reducing the likelihood of faults.
Economical price: Compared to other types of pneumatic actuators, diaphragm actuators are usually less expensive.
Easy maintenance: The simple design makes maintenance and part replacement easy.
Wide application: Suitable for occasions requiring precise control but with small thrust, such as small valves and light-load applications.
3. Actuation Forms
Direct-acting actuator: When the signal pressure increases, the valve stem moves downward. Signal pressure is introduced into the chamber above the corrugated diaphragm.
Reverse-acting actuator: When the signal pressure increases, the valve stem moves upward. Signal pressure is introduced into the chamber below the corrugated diaphragm. By changing parts, diaphragm actuators can be interchanged between direct and reverse action, increasing their flexibility and application range.
Piston Actuators
Piston actuators are pneumatic actuators that generate thrust through the movement of the piston inside the cylinder. Compared with diaphragm actuators, they can provide greater output force and are suitable for occasions requiring large thrust.
1. Working Principle
The main components of the piston actuator include the cylinder, piston, and push rod. The working principle is as follows:
Signal pressure application: Pneumatic signal pressure is applied to one side of the cylinder, causing the piston to move inside the cylinder.
Piston movement: The signal pressure generates thrust and moves the piston along the axis of the cylinder.
Push rod action: The movement of the piston is transmitted to the valve through the push rod, pushing the valve to open or adjust.
Valve action: The movement of the push rod causes the valve opening to change, thereby regulating the flow or pressure of the fluid.
2. Main Advantages
Piston actuators have the following advantages:
High thrust output: Capable of providing significant thrust, suitable for applications requiring a large torque.
Stability: Offers stable operation and high reliability due to its structure and working principle.
Wide application range: Suitable for large-caliber, high-pressure drop control, or butterfly valves that require a large thrust.
3. Basic Types
Two-way type: The piston moves between the high-pressure and low-pressure sides, mainly operated according to the input pressure difference.
Proportional type: Based on the two-way type, it adds a valve positioner, making the displacement of the push rod proportional to the signal pressure, improving control accuracy.
Rack-and-Pinion Actuators
Rack-and-pinion actuators are pneumatic actuators that drive the rotation of a small gear by the linear movement of the piston. They are widely favored for their compact structure, stable operation, and durability, suitable for various industrial application environments.
1. Working Principle
The rack-and-pinion actuator controls the valve through the following process:
Pneumatic drive: Pneumatic signal pressure acts on the piston inside the cylinder, causing it to move linearly.
Piston movement: The linear movement of the piston is transmitted to the small gear through the connected rack.
Gear rotation: The meshing of the rack with the small gear converts the linear movement of the piston into the rotational movement of the small gear.
Valve control: The rotation of the small gear drives the connected valve to open or close. This mechanism enables the rack-and-pinion actuator to efficiently convert pneumatic pressure into precise control of the valve.
2. Main Advantages
Rack-and-pinion actuators have the following advantages:
Compact structure: The design is compact, saving space, suitable for installation in narrow spaces.
Stable operation: Operates smoothly and reliably, suitable for various industrial environments.
High efficiency: Provides stable output force and precise control.
Durability: Uses advanced anti-corrosion treatment technology, capable of long-term operation in harsh environments.
Strong adaptability: Can cope with high and low temperatures as well as various special stroke application scenarios.
Pneumatic actuators play an important role in industrial automation, with different types of actuating mechanisms meeting various application needs. Diaphragm actuators are suitable for occasions requiring small thrust and high precision, piston actuators are suitable for applications requiring large thrust, and rack-and-pinion actuators are widely used in various operating environments with their efficient, reliable, and durable characteristics. Choosing the right pneumatic actuator can significantly improve the efficiency and stability of the system.
