Solenoid valve

Electromagnetic valve is an industrial equipment controlled by electromagnetism. It is an automatic basic component used to control fluid. It belongs to actuator and is not limited to hydraulic and pneumatic. It is used to adjust the direction, flow, speed and other parameters of the medium in the industrial control system. Solenoid valve can cooperate with different circuits to achieve the desired control, and the control accuracy and flexibility can be guaranteed. There are many kinds of solenoid valves. Different solenoid valves play a role in different positions of the control system. The most commonly used are one-way valve, safety valve, direction control valve, speed control valve, etc.

Working principle

There are closed cavities in the solenoid valve, and through holes are opened at different positions. Each hole is connected with different fluid medium pipes (such as compressed air or oil). The piston is in the middle of the cavity, and two electromagnets are on both sides. The valve body will be attracted to which side when the magnet coil is energized. The valve body can be opened or closed by controlling the movement of the valve body If it is normally open, compressed air or hydraulic oil will enter different exhaust pipes or oil drain pipes, and then the piston of (air and oil) cylinder will be pushed by the pressure of medium (compressed air or oil). The piston will drive the piston rod, and the piston rod will drive the mechanical device. In this way, the mechanical movement is controlled by controlling the current of electromagnet.

2 main classification

1. Solenoid valves are divided into three categories in principle

1) Direct acting solenoid valve:

Principle: when electrified, the electromagnetic coil produces electromagnetic force to lift the closing part from the valve seat and open the valve; when the power is off, the electromagnetic force disappears, and the spring presses the closing part on the valve seat, and the valve is closed.

Features: in vacuum, negative pressure, zero pressure can work normally, but the diameter is generally less than 25 mm.

2) Step by step direct acting solenoid valve:

Principle: it is a combination of direct acting and pilot type. When there is no pressure difference between the inlet and outlet, the electromagnetic force will directly lift the small pilot valve and the closing part of the main valve in turn, and the valve will be opened. When the inlet and outlet reach the start-up pressure difference, after power on, the electromagnetic force pilot small valve, the pressure of the lower chamber of the main valve rises, and the pressure of the upper chamber decreases, so as to push the main valve upward by using the pressure difference; when the power is off, the pilot valve uses the spring force or medium pressure to push the closing part and move downward to close the valve.

Features: it can also operate under zero pressure difference, vacuum and high pressure, but the power is large, so it must be installed horizontally.

3) Pilot operated solenoid valve:

Principle: when electrified, electromagnetic force will open the pilot hole, the pressure of upper chamber will drop rapidly, and it will be closed When the power is cut off, the spring force will close the pilot hole, and the inlet pressure will quickly form a low pressure difference around the valve closing piece, and the fluid pressure will push the closing piece to move downward to close the valve.

Features: the upper limit of fluid pressure range is high, which can be installed arbitrarily (need to be customized), but must meet the condition of fluid pressure difference.

2. According to the difference of valve structure and material and principle, the solenoid valve can be divided into six branches: direct acting diaphragm structure, step-by-step direct acting diaphragm structure, pilot diaphragm structure, direct acting piston structure, step-by-step direct acting piston structure and pilot piston structure.

3. Solenoid valves are classified according to their functions: water solenoid valve, steam solenoid valve, refrigeration solenoid valve, low temperature solenoid valve, gas solenoid valve, fire solenoid valve, ammonia solenoid valve, gas solenoid valve, liquid solenoid valve, micro solenoid valve, pulse solenoid valve, normally open solenoid valve of hydraulic solenoid valve, oil solenoid valve, DC solenoid valve, high-pressure solenoid valve, explosion-proof solenoid valve, etc.