# Hydraulic Power Pack – Volume flow

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### Volume characteristic curve of a typical hydraulic power pack

We want to record the volume flow as a function of the pressure p. We increase the pressure in the system using a shut-off valve connected in series. For this, see the measuring circuit. We transfer the measured values Q = f(p), i.e. volume flow as a function of pressure p, to an Excel spreadsheet.

We calculate the hydraulic power. For this we use a numerical equation that is frequently used in practice:

Phydr = (p × Q) / 600                  p in bar,  Q in l/min,  P in kW Hydraulic Power Pack - Characteristic Curve - Volume Flow as a function of Pressure

• The volume flow is almost constant up to around 50 bars. However, if you look closely, you can see a slight drop. Explain it!
• Above around 50 bars, the volume flow in the hydraulic load circuit drops rapidly. What is the cause of this rapid drop in volume flow? Why does the performance curve also have this "kink" at 50 bars?

Template Excel file for recording the Volume flow characteristic curve of a Hydraulic Power Pack for download here:

Hydraulic Pump - Volume flow characteristic curve

The experiment is explained in the following video from minute 2:42, as well as the function of the pressure relief valve, which is installed in the hydraulic unit:

0:00 Introduction Hydraulic Power Pack

0:38 Components and its function within the Hydraulic Power Unit

1:58 Hydraulic Power Pack working

2:42 Function of the Pressure relief valve

4:07 Hydraulic Circuit with a cylinder as actor