Do you know the pressure relief valve?
The purpose of hydraulic pressure relief valves is to limit the discharge pressure of the active pump to the permitted value. To do so, the valve lets the hydraulic oil escape out of the hydraulic chamber and into the reservoir upon reaching a certain pressure level. As a result, the displacer can no longer cause another pressure increase.
Most hydraulic pressure relief valves integrated into the pump head are used primarily to protect the pump head and drive unit and not to protect the system in which the pump is being operated. Without pressure limitation, if the permitted discharge pressure is exceeded, this would result in leaks at the pump head, damage to components or overloading of the drive. In principle, pressure relief valves are designed so that the entire stroke volume of the pump head can be discharged without causing additional, impermissible pressure increases.
Pressure relief valves are available in different designs, both with regard to their response behavior as well as their constructive design. A few designs are shown in the figure. During flow, pressure relief valves may exhibit a proportional characteristic with respect to the ratio of flow rate to pressure difference, or what is called a high-stroke characteristic, which entails a significant drop in pressure difference after activation.
Depending on the application, pressure range and seal technology used, pressure relief valves can be screwed in, flange-mounted or integrated into the housing. Combinations with other hydraulic valve functions may also be implemented in a housing or assembly.