Bosch Rexroth R901220879

General information Pressure valves type KAV are pilot-operated pressure cut-off valves with steplessly adjustable switching pressure differentials. They basically consist of pilot control stage (1) and main stage (2). Function The pump flow (main port ➀) is introduced into the accumulator of the system via main port ➂. If the pressure at the actuator in main port ➂ exceeds the set top switching pressure, the connection to Y (main port ➃) and T (main port ➁) is opened and the pump flow is switched to depressurized circulation (➀ to ➁). If the pressure at the actuator in main port ➂ falls below the set bottom switching pressure, the connection to Y (main port ➃) and T (main port ➁) is closed and the pump flow is directed back into the accumulator of the system. If used as accumulator charging valve, an additional check valve (7) is required to block the connection from main port ➂ to main port ➀ to prevent return flow of the accumulator volume. If used for depressurized pump start-up, an additional bore Z is required in the mounting cavity (see mounting cavity) for use of port Z at the valve. Between Z and Y (main port ➃), a directional valve (8) is to be switched to enable remote-controlled shut-off (from main port ➀ to main port ➁) under the set switching pressure. Setting the switching pressure differential: Notice! At the factory, the valves are set at nominal pressure to a switching pressure differential of approx. 10 % to 12 %. A setting of 8 % to 50 % of the nominal pressure is possible. On delivery, the adjustment spindle (3) is set to the minimum adjustable top switching pressure, i.e., the adjustment spindle is screwed out up to the limit stop. By screwing in the adjustment spindle (3), the top switching pressure may be increased. By screwing in the adjustment spindle (4), the bottom switching pressure is increased and the switching pressure differential reduced. Screwing out the adjustment spindle (4) reduced the bottom switching pressure and the switching pressure differential is increased. The pressure adjustment is secured by means of the clamping screw (6) and the lock nut (5). Possible setting range, refer to characteristic curve "switching pressure differential".

➀	Main port 1 (P)
➁	Main port 2 (T)
➂	Main port 3 (X, A)
➃	Main port 4 (Y)

1) Port Z can be applied in case of use for depressurized pump start-up in connection with a directional valve (see mounting cavity).