Pressure relief valve for the primary pressure setting at the hydraulic pumps and the pressure protection of the hydraulic drives, hydraulic components.

In the basic valve position, the hydraulic power of the hydraulic accumulator (7) acts on the piston valve (4) and transfers it to the valve piston (3). The valve seat (2) and the valve piston (3) form the valve seal at the conical surface. On the gas side, the hydraulic accumulator (7) has been prefilled with nitrogen and is preloaded hydraulically with the pressure setting on the liquid-side until the requested preset pressure «Pe» is reached. The gas within the accumulator is compressible and acts as a flexible spring.

Within the operation of the valve, the system pressure «Ps» enters the valve body (1) at the P-connector generating a hydraulic (opening) force at the valve seat area of the valve piston (3). The piston valve (4) maintains the valve piston (3) in the shut off basic position as long as the hydraulic opening force is < than the closing force at the piston valve (4). If the system pressure «Ps» increases to the extent that the force ratio reverses to be opening force > closing force, then the valve piston (3) is pressed out of the basic position, lines P and T are connected thus opening the valve. The valve opening increases proportionally with increasing system pressure until the maximum admissible volume flow for the valve has been reached, see Valve characteristic.

The pressure of the valve is set via the adjustment valves (5, 6). Thus, the pressure of the accumulator (7) is set. Depending on the pressure setting of the accumulator a hydraulic power is generated, which is transferred to the valve piston (3). From the control ratio «SK» (see Technical data) and the preset pressure «Pe» follows the required accumulator pressure «Pap».