R901003388 Bosch Rexroth Pressure relief valve

Pump safety blocks of types DBA/DBAW are pilot-operated pressure relief valves which are integrated into a block and intended to be mounted directly onto the SAE pressure port of pumps. They are used for limiting (DBA) or limiting and magnetically unloading (DBAW) the operating pressure. Pump safety blocks (DBA) basically consist of a valve block (1), main spool insert (3) and pilot control valve (2) with adjustment type for pressure adjustment. The valve housing has a port P for the hydraulic fluid input and port P1 for the output. In a branch of the through-bore between these two ports there is the main spool insert. When this is open there is a connection to port T (tank line). Pump safety block type DBA The pressure applied in the through-bore acts on the main spool (3). At the same time, pressure is applied to the spring-loaded side of the main spool (3) and to the ball (8) in the pilot control valve (2) via the control lines (6) and (7) which are equipped with nozzles (4) and (5). If the pressure in the through-bore exceeds the value set at spring (9), ball (8) opens against spring (9). The signal for this is provided internally from the through-bore via control lines (10) and (6). The hydraulic fluid on the spring-loaded side of main spool (3) now flows via the control line (7), nozzle bore (11) and ball (8) into the spring chamber (12). From here, it is fed into the tank, either internally for type DBA…– via control line (13), or externally for type DBA…Y via control line (14). Nozzles (4) and (5) cause a pressure drop to occur at the main spool (3), hence the connection from channel P to channel T opens. The hydraulic fluid now flows from channel P to channel T, whilst the set operating pressure is maintained. Port (15) can be used for remote control purposes. If a pressure load cell or a pressure gauge shut-off valve is to be connected here, then version SO616 – without nozzle (4) – must be ordered. This prevents delays in the pressure build-up or brief pressure drops when the pressure gauge shut-off valve is operated. Pump safety block type DBAR (with check valve) The integrated check valve maintains the system pressure when the pump is disconnected and prevents the hydraulic fluid from returning to the pump. If this valve is selected, no separate check valve is needed. Pump safety block type DBAW In addition, it can be switched from the pressure limiting function to depressurized circulation by controlling the built-on directional valve (16). Thus, a depressurized start-up of the pump is possible. Pump safety block with switching shock damping (sandwich plate) Version "S6E…R12" and "S6SM…B12" The opening of the connection from B2 to B1 or P2 to P1 is delayed by means of the switching shock damping valve (17). Pressure peaks and acoustic decompression shocks in the return line can thus be avoided. It is installed between the pilot control valve (2) and the directional valve (16). The degree of damping (decompression shock) is determined by the size of the nozzle (18). By default, a nozzle Ø1,2 mm is installed (ordering code "..R12.." or "..B12..").