Solenoid valve is an automatic basic element used to control the direction of fluid, belonging to actuator; It is usually used in mechanical control and industry
Above the valve, the medium direction is controlled, so as to control the valve switch.

Solenoid valves are divided into three categories in principle:

1)    direct acting solenoid valve:

Principle: when energized, the solenoid coil generates electromagnetic force to lift the closing part from the valve seat and open the valve; when powered 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.

2)    distribution solenoid valve 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 solenoid force will directly lift the small pilot valve and the closing parts of the main valve upward and open the valve. When the inlet and outlet reach the starting pressure difference, the solenoid 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 fall, so as to facilitate the opening of the valve Push the main valve upward with differential pressure; when power is 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 act when there is zero differential pressure or vacuum and high pressure, but the power is large, so it must be installed horizontally.

3)    pilot solenoid valve:

Principle: when power is on, the solenoid force opens the pilot hole and the pressure in the upper chamber drops rapidly, The pressure difference between the lower part and the higher part is formed around the closing part, the fluid pressure pushes the closing part to move upward, and the valve opens; in case of power failure, the spring force closes the pilot hole, the inlet pressure quickly forms the pressure difference between the lower part and the upper part around the valve closing part through the bypass hole, and the fluid pressure pushes the closing part to move downward to close the valve.

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