working principle:
1. Direct acting solenoid valve
Principle: When a normally closed direct acting solenoid valve is energized, the solenoid coil generates electromagnetic suction to lift the valve core, causing the sealing element on the valve core to leave the valve seat and open the valve; When the power is cut off, the electromagnetic force disappears, and the sealing element on the valve core is pressed against the valve seat by the spring force, causing the valve to close. Characteristics of the normally open type: It can work normally under vacuum, negative pressure, and zero pressure difference. The larger the valve diameter, the larger the volume and power of the electromagnetic head. The direct acting solenoid valve produced by our company with imported technology can be used for 1.33 × 10-4 Mpa vacuum.
2. Step by step direct acting solenoid valve (i.e. recoil type)
Principle: Its principle is a combination of direct action and pilot action. When powered on, the solenoid valve first opens the auxiliary valve. The lower chamber pressure of the main valve is greater than the upper chamber pressure, and the valve is opened by the simultaneous action of pressure difference and electromagnetic force; When the power is cut off, the auxiliary valve uses spring force or medium pressure to push the sealing element to close and move downwards to close the valve port. Characteristics: It can work reliably even at zero pressure difference or at a certain pressure. Generally, the working pressure difference does not exceed 0.6 MPa, but the electromagnetic head has a large power and volume, requiring vertical installation.
3. Pilot operated solenoid valve
Principle: When powered on, the electromagnetic force drives the pilot valve to open the pilot valve. The pressure in the upper chamber of the main valve rapidly decreases, forming a pressure difference in the upper and lower chambers of the main valve. With the help of the medium pressure, the main valve closing member moves upward, and the valve opens; When the power is cut off, the spring force closes the pilot valve, and the inlet medium pressure quickly enters the upper chamber of the main valve through the throttle hole, forming a pressure difference in the upper chamber and causing the main valve to close. Features: Small size, low power, but limited range of medium pressure difference, meeting the pressure difference condition (0.01MPa).
Electromagnetic valve is an industrial equipment controlled by electromagnetic force, used as an automation basic component for controlling fluids. It belongs to actuators and is not limited to hydraulic and pneumatic systems. Electromagnetic valves are widely used in many products due to their precision and flexibility in control. As a gatekeeper for circuit safety, the selection and application of solenoid valves should be safe and reliable. The required model and function of solenoid valves may vary in different control systems, so choose the appropriate solenoid valve based on practical requirements.
Four major selection principles
Security:
1. Corrosive media: Plastic king solenoid valves and all stainless steel (316) should be selected; For strongly corrosive media, use isolation membrane type. Neutral medium, copper alloy can also be used as the valve body material for solenoid valves. Ammonia valves cannot use copper materials.
2. High temperature steam medium: Stainless steel or cast steel valve bodies should be selected, and polytetrafluoroethylene seals should be used. Copper alloy valve bodies can also be used for ordinary high temperatures (below 180 degrees). High temperature (350 degrees) thermal oil and steam are sealed with hard seals and heat sinks are added.
3. Explosive environment: Choose products with corresponding explosion-proof levels, and choose waterproof and dustproof varieties for outdoor installation or dusty occasions.
4. The working pressure of the solenoid valve should exceed the high working pressure inside the pipe
Applicability：
1. The selection of electromagnetic coils for products with different medium temperatures will also vary (for example, high-temperature solenoid valves must be equipped with high-temperature coils), otherwise the coils will burn out, seriously affecting their lifespan.
2. Working pressure difference: Pilot operated solenoid valves can be selected for low working pressure differences above 0.03Mpa; Select direct acting or step-by-step direct acting solenoid valves for low working pressure differentials close to or less than zero.
3. Select the nominal diameter (DN) based on the flow rate and valve Kv value, or choose the same pipe inner diameter.
4. In environments with high relative humidity and water droplets and rain, waterproof solenoid valves should be selected.
5. The voltage specification should preferably use AC220V or DC24V.