Overview of pneumatic systems

Gas exists in space in a certain state, which is usually represented by three parameters: pressure, temperature, and volume. The process of a gas changing from one state to another is called the gas state change process. The relationship between various parameters during or after a gas state change in equilibrium is described using the gas state equation. Natural air can be regarded as an ideal gas (regardless of viscosity).

Pneumatic transmission and control use dry air (air that removes moisture and does not contain water vapor) as the working medium.

Air source power device refers to a device that provides the pressure and flow rate of compressed air required for execution or work purposes. It is the core component of pneumatic transmission and control systems, usually referring to an air compressor. Generally, airflow conveying machinery with an exhaust pressure higher than 0.2Mpa is called an air compressor (referred to as an air compressor). Air compressors can be divided into two types based on their working principles: speed type and solvent type. Compressed air is compressed from the atmosphere, which is mixed with impurities such as dust and water vapor. After compression, it is mixed with compressed air. The compressed air output by the air compressor must be purified and dried, that is, to remove impurities such as dust, water, and oil mixed in the compressed air before it can be used as a power source for the pneumatic system.

The pressure at the inlet and outlet is relatively high, forming a negative pressure (vacuum) at the inlet, and the airflow conveying machinery that is directly connected to the atmosphere at the exhaust is called a vacuum pump. It is used as a power source in the vacuum adsorption system.

Pneumatic actuators are divided into oil fed pneumatic actuators, oil free pneumatic actuators, and oil free lubricated pneumatic actuators in the form of lubrication. According to the nature of motion, it can be divided into cylinders, pneumatic motors, and swing motors. The pneumatic actuator is a transmission device that converts the pressure energy of compressed air into mechanical energy, enabling linear reciprocating motion, swinging, rotating motion, or impact action.

Pneumatic control components are various pneumatic devices used for signal sensing and conversion, logic control, parameter adjustment, etc., to ensure that the pneumatic actuator operates correctly and reliably according to the program specified in the pneumatic control system. Pneumatic control can usually be divided into two categories: intermittent control and continuous control.

In intermittent control (also known as switch control) systems, pressure and flow regulation, as well as control of airflow direction and on/off program, are usually required. Pressure control valves, flow control valves, switch type directional control valves, and pneumatic logic components are used, respectively. In a continuous control system, in addition to pressure and flow regulating control valves, servo/proportional control valves should also be used for continuous control of the system. Pneumatic sensing components and conversion components are pneumatic sensing components that detect controlled parameters and convert them into pressure signals (such as various sensors and stroke valves), as well as components that convert gas signals into electrical, hydraulic, and other signals.

Pneumatic auxiliary components are devices required for purifying, lubricating, silencing compressed air, and for connecting components. Such as filters, oil misters, blowers, mufflers, converters, and pipe fittings.

Pneumatic system is a transmission system that uses air as the working medium. In general pneumatic control systems for pneumatic transmission, in order to achieve the purpose of automatic control in scientific research and production processes, it usually consists of several parts of devices and components such as pressure generation devices, air source processing devices, pneumatic control components, pneumatic execution components, and pneumatic accessories. Including two parts: pneumatic transmission system and pneumatic control system.

The pneumatic transmission system is divided into compressor direct supply, storage tank supply, and pipeline supply according to the gas supply method; According to the motion characteristics of the actuator, it can be divided into: direct reciprocating motion, rotary motion, and swinging motion; According to the working medium circulation method, it can be divided into open circulation and closed circulation.

The air pressure control system includes an air valve control system (including both electronic and pneumatic control), a logic component control system, and a jet component control system. A typical pneumatic system consists of an electric motor, an air compressor, a pressure control valve, a directional control valve, a flow control valve, a stroke valve, logic components, cylinders, silencers, oil mist eliminators, oil-water separators, shut-off valves, pneumatic sensors, pressure gauges, air storage tanks, safety valves, etc.

Advantages and disadvantages of pneumatic systems

Advantages:

Simple structure, easy maintenance, low cost, fast investment recovery, and good adaptability to working environment; Can work reliably in environments with a wide range of temperature changes, high humidity, high dust, vibration, etc; Slight leakage will not pollute the environment, there is no risk of fire and explosion, and it is safe to use; Long working life, electromagnetic valve life can reach 30-50 million times, and cylinder life can reach 2000-600km; The output speed of the actuator is high, and the linear motion can reach 15m/s; Equipped with overload protection capability, the actuator will automatically stop when overloaded, without any risk of damage, and will remain stationary under load when the power is insufficient. Disadvantages:

Due to the compressibility of air, the stability of the movement speed of working components is poor; Low working pressure, the output thrust of pneumatic actuator is smaller than that of hydraulic transmission; The speed of long-distance signal transmission is relatively slow, and the transmission of atmospheric pressure signals is not suitable for complex circuits with high-speed transmission; Due to low working pressure and unsuitable structural dimensions, the output force is usually not greater than 10-40kN.