In order to choose your hydraulic unit correctly, it is important to start by defining what the nominal power required will be according to the desired flow rate and pressure in bars, which depends on the efforts to be applied:
- Nominal [TB1] power: indicated in watts (W) or kilowatts (kW), it is the power of the motor that drives the hydraulic pump.
- Nominal flow rate: expressed in liters per second (l/s) or liters per minute (l/min), it is the volume of liquid that the pump can send into the system in a given time.
- Nominal pressure: expressed in pascals (Pa) or bars, it is the force that the hydraulic unit can withstand and depends on the power of the engine.
It is important to properly calculate the power of your unit because, even if you may find it advantageous to have extra power, for example to meet other needs later on, excessive pressure can damage the components of your hydraulic system. However, if your hydraulic power unit is not powerful enough, the equipment it needs to supply will not be able to operate properly. You must also estimate the size of the tank, as its capacity must be sufficient to supply the entire hydraulic system according to the desired flow rate and utilization rate.
It is also essential to choose your hydraulic power unit according to its use (continuous or intermittent). Use beyond the operating rate specified by the manufacturer may result in overheating, evaporation of the hydraulic fluid and damage to the engine. DIN VDE 0530 defines the operating rates as follows:
- S 1: Continuous duty
- S 2: Short-term duty that generates little or no heating (running time depending on the load).
- S 3: Intermittent duty in order to control heating (running time as a percentage of a 10-minute cycle).
Depending on the available energy sources, you must then choose the type of motorization: electric, combustion or air-driven.
Finally, depending on the conditions your hydraulic power unit will have to operate in, you can determine the options you will need. For example, you must plan for oil preheating if the hydraulic power unit is to operate at negative temperatures.