Solenoid valve is the use of electromagnetic principle to control the flow of fluid automation components. Its working principle is based on the suction and release of the solenoid, by changing the position of the valve spool to control the passage or direction of the fluid. When the coil is energised, an electromagnetic force is generated which causes the spool to move, thus changing the state of the fluid passage. The solenoid control principle is characterised by rapid response and precise control.

Different types of solenoid valves have different operating principles. For example, direct-acting solenoid valves directly drive the spool movement through electromagnetic force; step-by-step direct-acting solenoid valves use a combination of pilot and main valves to achieve high-pressure and large-diameter fluid control; pilot-operated solenoid valves use the pressure difference between the pilot hole and the main valve to control the fluid. These different types of solenoid valves have a wide range of applications in the field of industrial automation.

2. Structure of solenoid valves
The basic structure of the solenoid valve includes the valve body, spool, coil, spring and other components. Valve body is the main part of the fluid channel, bearing the fluid pressure and temperature; spool is the key part of the control of the fluid or direction, its movement determines the opening and closing of the fluid channel; coil is the part of the electromagnetic force, through the change of the current to control the spool of the valve movement; spring plays a role in resetting and maintaining the stability of the spool.

In the construction of the solenoid valve, there are some key components such as seals, screens and so on. Seals are used to ensure the sealing between the valve body and spool to prevent fluid leakage; screen is used to filter impurities in the fluid to protect the internal parts of the solenoid valve from damage.

3. Solenoid valve interface and diameter
Solenoid valve interface size and type according to the needs of the fluid pipeline and design. Common interface size G1/8, G1/4, G3/8, etc., interface types include internal thread, flange and so on. These interface sizes and types ensure the smooth connection between the solenoid valve and the fluid pipeline.

Through diameter refers to the diameter of the internal fluid passage of the solenoid valve, which determines the fluid flow and pressure loss. The size of the through diameter according to the fluid parameters and piping parameters to be selected to ensure the smooth flow of fluid inside the solenoid valve. Selection of the diameter also need to consider the size of the impurity particles in the fluid, to avoid particles blocking the channel. 4.

4. Solenoid valve selection parameters
In the selection, the first thing to consider is the pipeline parameters, including pipe size, connection, etc., in order to ensure that the solenoid valve can be smoothly connected to the existing piping system. Secondly, fluid parameters such as media type, temperature, viscosity, etc. is also a key consideration, they directly affect the solenoid valve material selection and sealing performance.

Pressure parameters and electrical parameters should not be ignored. Pressure parameters include the working pressure range and pressure fluctuations, which determines the solenoid valve pressure capacity and stability; and electrical parameters such as power supply voltage, frequency, etc., need to match with the site power supply conditions to ensure that the solenoid valve's normal operation.

The choice of action depends on the specific application scenarios, such as normally open, normally closed or switching type. Special requirements such as explosion-proof, anti-corrosion, etc., also need to be fully considered in the selection to meet the safety and use of specific environmental needs.

Solenoid valve selection guide
In the field of industrial automation, solenoid valve as a key component of fluid control, its selection is particularly important. A proper selection can ensure the stable operation of the system, while an improper selection may lead to equipment failure or even safety accidents. Therefore, in the solenoid valve selection, must follow certain principles and steps, and pay attention to the relevant selection matters.

1. Selection principles
Safety is the primary principle of solenoid valve selection. Must ensure that the selected solenoid valve in the process of work will not cause harm to personnel and equipment. Applicability means that the solenoid valve must meet the control requirements of the system, can reliably control the fluid on and off and flow. Reliability requires that the solenoid valve has a long service life and low failure rate, in order to reduce maintenance costs. Economy is to meet the above requirements, as far as possible under the premise of choosing a reasonable price, cost-effective products.

2. Selection steps
First of all, you need to define the working conditions and requirements of the system, including the nature of the fluid, temperature, pressure and other parameters, as well as the system's control mode, frequency of action, etc.. Then, according to these conditions and requirements to select the appropriate type of solenoid valve, such as two-position three-way, two-position five-way and so on. Next, determine the specifications and dimensions of the solenoid valve, including interface size, through diameter, etc.. Finally, according to the actual need to select additional features and options, such as manual operation, explosion-proof, etc..

3. Selection considerations
In the selection process, special attention needs to be paid to the following aspects: first of all, corrosive media and material selection. For corrosive media, should choose corrosion-resistant materials made of solenoid valves, such as plastic king or all stainless steel products. Secondly, the explosive environment and explosion-proof grade. In explosive environments, must be selected to meet the requirements of the corresponding explosion-proof level of solenoid valve. In addition, it is also necessary to consider the environmental conditions and the adaptability of the solenoid valve, the power supply conditions and the matching of the solenoid valve, the action reliability and the protection of important occasions, as well as brand quality and after-sales service considerations and other factors. Only comprehensive consideration of these factors, in order to select both safe and affordable solenoid valve products.