Classification and working principle of solenoid valve

Tracing the history of the development of solenoid valves, so far, domestic and foreign solenoid valves from the principle is divided into three categories, namely: direct-acting, step-by-step direct-acting, pilot type .

First, direct-acting solenoid valve 

Principle: When energized, the solenoid coil generates electromagnetic force to lift the closing member from the valve seat, the valve opens; when disconnected, the electromagnetic force disappears and the spring force presses the closing member on the valve seat, the valve closes. 

Features: in the vacuum, negative pressure, zero pressure can work properly, but the general diameter does not exceed 25mm. 

Second, step-by-step direct-acting solenoid valve 

Principle: It is a combination of direct-acting and piloting principle, when the inlet and outlet pressure difference ≤ 0.05Mpa, when energized, the electromagnetic force directly to the pilot small valve and the main valve closure parts in turn upward lift, the valve open. When the inlet and outlet pressure difference > 0.05Mpa, when the power is applied, the electromagnetic force opens the pilot valve first, the pressure in the lower chamber of the main valve rises and the pressure in the upper chamber falls, thus using the pressure difference to push the main valve upward; when the power is off, the pilot valve and the main valve use the spring force or medium pressure to push the closing member and move downward to close the valve. 

Features: in zero differential pressure or vacuum, high pressure can also work reliably, but the power is larger, requiring vertical installation. 

Third, the pilot operated solenoid valve 

Principle: When energized, the electromagnetic force opens the pilot hole, the pressure in the upper chamber drops rapidly, forming a low pressure differential around the closing member, pushing the closing member to move upward and open the valve; when disconnected, the spring force closes the pilot hole, the inlet pressure through the bypass hole quickly into the upper chamber to form a low pressure differential around the closing member, pushing the closing member to move downward and close the valve. 

Features: the upper limit of the fluid pressure range is high, but must meet the fluid pressure differential conditions.

Fourth, the solenoid valve open and closed state

Commonly used solenoid valve is mostly diaphragm valve, its working principle is: the valve body is divided into two chambers, the middle for the diaphragm, under the same conditions of water pressure, due to the diaphragm up and down the force area is different and the pressure difference, to cut off the flow of water.

Burner solenoid valve open state: when the remote controller to give an electrical signal or manually rotate the solenoid head, drainage channel open, the upper diaphragm chamber water discharge, indoor pressure decreases, the pressure acting on the upper diaphragm becomes smaller, under the action of upstream pressure to push the diaphragm upward movement, open the pipeline channel.

Solenoid valve closed state: manually close or disconnect the solenoid head electrical signal, so that the drainage channel is closed, the upper diaphragm chamber slowly filled with water, wait until the diaphragm up and down the same pressure, due to the diaphragm on the upper side of the force area is larger, so that the diaphragm downward movement, close the pipeline channel.