Pilot operated valves are characterized by their simple, solid design. As sealing elements, the options are a diaphragm for pressure up to 20 bar or a piston for pressure up to 40 bar.
Valves of this type need a pressure differential of the operating pressure for opening and closing. The minimum required pressure is specified as minimum pressure in the technical data sheet.
The solenoid system only has a pilot function which relieves the main sealing element, i.e. the diaphragm or the piston. The medium pressure or the present pressure differential lifts the main seal.