Basic knowledge: Principles and types of solenoid valves

In the history of the development of solenoid valves, so far, the solenoid valves at home and abroad are divided into three major categories (ie, direct-acting, step-by-step pilot), and the differences in valve structure and materials. The difference in principle is divided into six sub-categories (direct-acting diaphragm structure, step-and-repeat structure, pilot-membrane structure, direct-acting piston structure, step-by-step direct-acting piston structure, and pilot piston structure).

Direct acting solenoid valve:

Principle: When energized, the electromagnetic coil generates electromagnetic force to lift the closing member from the valve seat, and the valve is opened; when the power is off, the electromagnetic force disappears, the spring presses the closing member against the valve seat, and the valve is closed.

Features: It can work normally under vacuum, negative pressure and zero pressure, but the diameter is generally not more than 25mm.

Distributed direct-acting solenoid valve:

Principle: It is a combination of direct motion and pilot type. When there is no pressure difference between the inlet and the outlet, after energization, the electromagnetic force directly lifts the pilot small valve and the main valve closing member upward, and the valve opens. When the inlet and outlet reach the starting pressure difference, after the energization, the electromagnetic force leads the small valve, the pressure of the lower chamber of the main valve rises, and the pressure of the upper chamber drops, so that the main valve is pushed upward by the pressure difference; when the power is off, the pilot valve uses the spring The force or medium pressure pushes the closure and moves down to close the valve.

Features: It can also be operated at zero differential pressure or vacuum or high pressure, but the power is large and requires horizontal installation.

Pilot solenoid valve:

Principle: When energized, the electromagnetic force opens the pilot hole, the pressure in the upper chamber drops rapidly, and a pressure difference between the lower part and the lower part is formed around the closing member. The fluid pressure pushes the closing member upward to move the valve to open; when the power is off, the spring force leads the pilot. The hole is closed, and the inlet pressure passes through the bypass hole. The rapid chamber forms a lower high and high pressure difference around the valve closing member, and the fluid pressure pushes the closing member downward to close the valve.

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