Pressure relief valve Bosch Rexroth DB20K

Pressure valves type DB..K.. are pilot-operated pressure relief valves for block design installation. They are used for system pressure limitation. The system pressure can be set via the adjustment type (4).
In the initial position the valves are closed. The pressure in main port 1 acts on the spool (1). At the same time, pressure is applied to the spring-loaded side of the spool (1) via nozzle (2) and to the pilot poppet (6) via nozzle (3). If the pressure in main port 1 exceeds the value set at spring (5), the pilot poppet (6) opens. Hydraulic fluid flows from the spring-loaded side of the spool (1) via nozzle (3) and channel (7) into the main port 3. The resulting pressure drop moves the spool (1) and thus opens the connection from main port 1 to 2 while maintaining the pressure set at spring (5).
Die pilot oil return from the two spring chambers is effected externally, via main port 3.
Notice:
Counter pressures (main port 3) add up to the set pressure.
Type DB 10 K2-4X/.YV