The working principle of solenoid valve

In principle,solenoid valves  are divided into three categories: direct-acting, stepwise direct-acting, and pilot-operated. The difference in valve structure and material and the difference in principle are divided into six sub-categories: direct-acting diaphragm structure, step-by-step direct-acting diaphragm structure, pilot diaphragm structure, direct-acting piston structure, and step-by-step Direct-acting piston structure, pilot piston structure.

1. Direct-acting solenoid valve

Principle: When energized, the solenoid valve coil generates electromagnetic force to lift the closing member from the valve seat, and the valve opens; when the power is off, the electromagnetic force disappears, and the spring force presses the closing member 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. Step-by-step direct-acting solenoid valve

Principle: It is a principle that combines direct action and pilot type. When there is no pressure difference between the inlet and the outlet, the electromagnetic force directly lifts the pilot small valve and the main valve closing member upwards in turn, and the valve opens. When the inlet and outlet reach the start-up pressure difference, after energization, the electromagnetic force first opens the pilot small valve, the main valve pressure rises, and the upper cavity pressure drops, so that the spring force or medium pressure is used to push the closing piece and move downward to close the valve. . Features: It can operate reliably under zero pressure, vacuum, or high pressure, but the power is large, and it must be installed horizontally.

Three, pilot solenoid valve

Principle: When the power is turned on, the electromagnetic force opens the pilot hole, the pressure in the upper chamber drops rapidly, and a high pressure difference is formed around the closing part. The fluid pressure pushes the closing part to move and the valve opens; when the power is off, the spring force pushes the pilot hole When closed, the inlet pressure quickly enters the upper chamber through the bypass hole to form a lower and upper pressure difference around the valve closing member, and the fluid pressure pushes the closing member to move downward to close the valve. Features: The upper limit of the fluid pressure range is high, and it can be installed arbitrarily (customization is required), but the fluid pressure difference condition must be met.