In indirectly operated two-way solenoid valves, the solenoid controls a small-diameter auxiliary (pilot) valve, which then controls a piston or diaphragm that is connected to the main valve's closing element and has a larger area than the seat of the auxiliary valve, thereby amplifying the signal. This makes it possible to control large forces acting on the closing element on the seats of the main valve of larger clearances with a small power input of the electromagnet coil.
The basic position of the valve, to which the main closing element of the valve is adjusted after the cancellation of the electrical signal, is provided by a spring acting on the piston or membrane of the closing element with the help of the pressure of the medium, therefore, for the adjustment of the closing element from the basic position, the prescribed pressure difference between the inlet and outlet sides must be ensured valve, so-called minimum pressure difference.
