The change in pressure in a hydraulic system without throttling or storage corresponds to the related change in load pressure (taking into account the pressure losses).
On accumulator supplies, however, this statement no longer applies, as the accumulator is generally pre-charged to the nominal pressure of the system. As on the hydropneumatic accumulators used today the accumulator pressure drops on the drawing usable volume (corresponds to the ratio of gas capacity to usable volume), the system pressure changes accordingly on drawing. The term impressed (pre-defined) pressure (Figure E 5) is used.
The term "constant pressure system" often used is not correct here, as the pressure does not remain constant. The system with impressed pressure is also termed a "(constant) pressure source".
Figure E 5: System with impressed pressure