Pilot-operated solenoid valve, when powered on,relying onthe electromagnetic force to lift the valve stem, pilot valve portopen. At this time, the upper chamber of the solenoid valvedepressurized through the pilot hole, forming an upper lowerheight around the main valve core. Under the pressure differ-ence, the fluid pressure pushes the main spool upward todrive main valve port open. When power goes off, under theaction of spring force and main spool gravity, the valve stemis reset, the pilot hole is closed, the spool moves down, andthe main valve port is closed. The pressure in the upperchamber of the solenoid valve increases, the fluid pressurepressurizes the main spool, and the seal is better.