Ningbo Zhanyue Hydraulic explained the working principle and classification of solenoid valves:
Solenoid valve is an industrial equipment controlled by electromagnetism and is an automatic basic element used to control fluid. It belongs to actuator and is not limited to hydraulic and pneumatic. It is used in industrial control system to adjust the direction, flow, speed and other parameters of medium. The solenoid valve can cooperate with different circuits to achieve the expected control, and the control accuracy and flexibility can be guaranteed. There are many kinds of solenoid valves. Different solenoid valves play different roles in different positions of the control system. The most commonly used are one-way valves, safety valves, directional control valves, speed control valves, etc. The solenoid valve has a closed cavity with through holes at different positions. Each hole is connected with different oil pipes. The piston is in the middle of the cavity, and two electromagnets are on both sides. The magnetic coil on which side energizes the valve body will be attracted to which side. Different oil drain holes will be opened or closed by controlling the movement of the valve body. The oil inlet hole is normally open, and the hydraulic oil will enter different oil drain pipes, and then the oil pressure will push the fire plug of the cylinder, The piston drives the piston rod, which drives the mechanical device. In this way, the mechanical movement is controlled by controlling the current of the electromagnet.
Direct acting solenoid valve
Principle: When energized, the solenoid coil generates electromagnetic force to lift the closing part from the valve seat, and the valve opens; When the power is cut off, the electromagnetic force disappears, the spring presses the closing part on the valve seat, and the valve closes.
Features: It can work normally under vacuum, negative pressure and zero pressure, but the diameter generally does not exceed 25mm.
Step-by-step direct-acting solenoid valve
Principle: It is a combination of direct-action and pilot type. When there is no pressure difference between the inlet and outlet, the electromagnetic force will directly lift the pilot small valve and the main valve closing part upward after energizing, and the valve will open. When the inlet and outlet reach the starting pressure difference, the electromagnetic force will pilot the small valve, the pressure in the lower chamber of the main valve will rise, and the pressure in the upper chamber will drop, so as to push the main valve upward by using the pressure difference; When the power is cut off, the pilot valve uses spring force or medium pressure to push the closing part and move downward to close the valve.
Features: It can also operate at zero differential pressure, vacuum and high pressure, but the power is large, so it must be installed horizontally.
Pilot solenoid valve
Principle: when energized, the electromagnetic force opens the pilot hole, and the pressure in the upper chamber drops rapidly, forming a high and low pressure difference around the closing part. The fluid pressure pushes the closing part upward, and the valve opens; When the power is cut off, the spring force closes the pilot hole, and the inlet pressure rapidly forms a pressure difference of lower and higher around the valve closing parts through the bypass hole. The fluid pressure pushes the valve closing parts downward to close the valve.
Features: The upper limit of the fluid pressure range is high, and can be installed arbitrarily (customized), but the fluid pressure differential condition must be met.
2. According to the difference in valve structure and material and principle, the solenoid valve can be divided into six sub-categories: 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, hydraulic solenoid valve normally open solenoid valve, oil solenoid valve, DC solenoid valve, high-pressure solenoid valve, explosion-proof solenoid valve, etc.
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