What are the different types of hydraulic power units?

Hydraulic power units supply pressurized hydraulic fluid to power hydraulic systems and components.    

 

 

Auto hoist power units

There are several different types of hydraulic power units:
1.    Electric motor-driven - The most common type.    Uses an electric motor to drive a hydraulic pump which pressurizes the fluid.    Can provide high pressures and flow rates.    Requires an external power source and electric motor.
2.    Engine-driven - Powered by an internal combustion engine instead of an electric motor.    Used where electricity is unavailable.    Provides hydraulic power independent of external power sources.    However, exhaust fumes have to be properly vented.
3.    Hand-operated - Uses manual pumping to pressurize the hydraulic fluid.    For applications where electric or engine power is not needed or available.    Limited to relatively low pressures and flow rates due to the amount of human power available.
4.    Pressure intensifiers - Use hydraulic power or an air drive to boost the pressure of a hydraulic system.    The power source drives hydraulic pumps which feed a low-pressure side of the intensifier.    The intensifier then boosts this to a higher pressure on its output side.    Used when very high pressures beyond the capacity of standard pumps are required.
5.    Accumulator-based - Uses pre-charged accumulators as an energy source instead of pumps and motors.    Accumulators drive the hydraulic system until their stored energy is depleted, at which point they are recharged.    Very quiet and portable but limited duration of operation.    Only practical for intermittent or low-power applications.
6.    Air-driven - Uses compressed air as the power source to drive a hydraulic pump and generate hydraulic power.    Can provide hydraulic power independent of electrical sources but requires a supply of compressed air.    Limited to moderate pressures and flows due to the characteristics of compressed air.