Solenoid valves are divided into three main categories from the principle:
1. Direct-acting solenoid valves
Principle: when energized, the solenoid coil generates an electromagnetic force to lift the shut-off piece from the valve seat, and the valve opens; when de-energized, the electromagnetic force disappears, and the spring presses the shut-off piece against the valve seat, and the valve closes.
Features: in a vacuum, negative pressure, zero pressure can work normally, but the diameter is generally not more than 25mm.
2. Step-by-step direct-acting solenoid valves
Principle: it is a combination of direct-acting and pilot-type principle, when there is no pressure difference between the inlet and the outlet, the energized, the electromagnetic force directly to the pilot and the main valve closure of the valve upward in turn to lift the valve open. When the inlet and outlet to start the pressure difference, energized, electromagnetic force pilot small valve, the main valve lower chamber pressure rises, the upper chamber pressure drops, thus using the pressure difference to push the main valve upward; power failure, the pilot valve using spring force or medium pressure to push the closing member, move downward, so that the valve is closed.
Features: in zero differential pressure or vacuum, high pressure can also be * action, but the power is larger, the requirement must be installed horizontally.
3. Pilot operated solenoid valve
Principle: when energized, the electromagnetic force to the pilot hole open, the upper chamber pressure drops rapidly, the formation of a low pressure differential around the closure of low and high in the fluid pressure to promote the closure of the piece to move upward, the valve is open; power failure, the spring force to the pilot hole is closed, the inlet pressure through the by-pass hole rapidly chamber in the closure of the valve around the formation of a low and high in the fluid pressure to push the closure of the piece to move downward, the valve closes; the inlet pressure through the by-pass hole to form a low and high in the chamber pressure differential around the valve piece. The fluid pressure pushes the closing member to move downward and close the valve.
Features: the upper limit of the fluid pressure range is higher, can be arbitrarily installed (need to be customized) but must meet the conditions of the fluid pressure difference.
Solenoid valve from the valve structure and materials on the different principles of difference, divided into six branches of subcategories:
Direct diaphragm structure, step-by-step direct diaphragm structure, pilot diaphragm structure, direct piston structure, step-by-step direct piston structure, pilot piston structure.
Solenoid valve according to the function classification:
Water solenoid valve, steam solenoid valve, refrigeration solenoid valve, cryogenic solenoid valve, gas solenoid valve, fire solenoid valve, solenoid valve, ammonia solenoid valve, gas solenoid valve, liquid solenoid valve, miniature solenoid valves, pulse solenoid valves, hydraulic solenoid valves Normally open solenoid valves, solenoid valve, oil solenoid valves, DC solenoid valves, high pressure solenoid valve, explosion-proof solenoid valves and so on.
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