What is the working principle of the pilot solenoid valve?

What is a pilot solenoid valve?
　　
Pilot solenoid valve, when energized, the valve stem is lifted by electromagnetic force, and the pilot valve port is opened. At this time, the upper cavity of the solenoid valve is relieved through the pilot hole, forming a high pressure difference around the main valve core, which acts on the pressure difference. When the power is turned off, under the action of the spring force and the gravity of the main spool, the valve stem is reset, the pressure in the upper chamber of the solenoid valve rises, and the fluid pressure pushes the main spool. Moving down, the main valve port is closed.

Principle of pilot solenoid valve
For medium with zero pressure difference or self-flow, direct-acting solenoid valves are generally used for small diameters; there is a pressure difference before and after the valve, and pilot solenoid valves are used for large diameters.

Features of pilot solenoid valve
The upper limit of the fluid pressure range is high, and it can be installed arbitrarily (customization is required) but must meet the fluid pressure difference condition.
Pilot diaphragm structure, low function.
The protective diaphragm structure design extends the service life twice.
The piping method can be installed at any angle. In order to enhance the life, it is best to connect the horizontal pipe with the coil facing upward.
The coil protection grade is IP65.
Applicable medium: liquid, water, hot water, gas, oil, gas, etc.