1, solenoid valves are divided into three categories in principle:
Direct acting solenoid valve
Principle: When electrifying, the electromagnetic coil generates electromagnetic force to lift the closing piece from the valve seat and open the valve; When the power is cut off, the electromagnetic force disappears, the spring presses the closing piece on the valve seat, and the valve closes.
Features: It can work normally under vacuum, negative pressure and zero pressure, but its diameter is generally less than 25mm.
Stepping direct-acting solenoid valve
Principle: It is a combination of direct-acting and pilot-acting. When there is no pressure difference between the inlet and outlet, the electromagnetic force directly lifts the pilot small valve and the main valve closing piece in turn, and the valve opens. When the inlet and outlet reach the starting pressure difference, the electromagnetic force guides the small valve, and the lower chamber pressure of the main valve increases and the upper chamber pressure decreases, so that the main valve is pushed upward by the pressure difference; When power is cut off, the pilot valve uses spring force or medium pressure to push the closing piece to move down and close the valve.
Features: It can operate under zero pressure difference, vacuum and high pressure, but it has high power and must be installed horizontally.
Pilot solenoid valve
Principle: When the power is on, the electromagnetic force opens the pilot hole, and the pressure in the upper chamber drops rapidly, forming a pressure difference between the upper and lower parts around the closing part, and the fluid pressure pushes the closing part to move upward, thus opening the valve; When power is cut off, the pilot hole is closed under the action of spring force, the inlet pressure quickly forms a low-high pressure difference around the closing valve through the bypass hole, and the fluid pressure pushes the closing piece to move downwards to close the valve.
Features: The upper limit of the fluid pressure range is high, and it can be installed (customized) at will, but the fluid pressure difference condition must be met.
2. According to different valve structures, materials and principles, solenoid valves can be divided into six 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 by function: 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, oil solenoid valve, DC solenoid valve, high pressure solenoid valve, explosion-proof solenoid valve, etc.