Basics of Hydraulic Power Units(HPU)

How important hydraulic fluid is, likewise is the hydraulic power unit. Most of the hydraulic systems that we commonly use will be having a hydraulic power unit. The primary function of this hydraulic power unit includes converting the mechanical energy to hydraulic energy. hese HPU’s assist to generate fluid flow in the system. Common applications that utilize hydraulic power units include tractor-mounted excavators, aerial work platforms, lifters, log loaders and more.

The HPU’s are self-contained units with interconnected components that are used when heavy lifting or repeated directional force are required. The major components of a hydraulic power unit are a primary power source, that can be either an AC/DC motor or an internal combustion engine; a hydraulic gear/vane/piston pump; a hydraulic reservoir that suits with your fluid requirements; filtration units and valves.

How does the hydraulic power unit work? The central part of this hydraulic power unit is the pump, which is driven by the primary power source(motor or internal combustion engine). The primary power source will convert the mechanical energy to fluid flow and the hydraulic fluid will be pumped to the hydraulic pump from the reservoir. The reservoir is selected on the basis of the desired application and the hydraulic pump selection depends on the pumping rate, pressure limits, and environment. This fluid will pass through filters and different control elements like check valves, directional control valves, pressure relief valves, etc… for maintaining the required direction and flow rate.


Based on the construction, hydraulic power units(HPU‘s) are classified into a single-acting hydraulic power pack and double-acting hydraulic power pack. The major difference between these two types of hydraulic power pack includes: in single-acting HPU, fluid pressure is applied only in any one end and the required power to push back the piston to its original position is provided by an external force. But in double-acting HPU, fluid pressure is applied alternatively on both ends of the piston for its extension and retraction.

Another classification of this hydraulic power unit(HPU) is based on its size. Micropower pack units, mini power pack units, standard hydraulic power pack units, and hydraulic power unit stations are the major categories on the basis of size. As the name suggests, the micropower pack units are compact in size and flexible. This HPU can easily integrated with single or double-acting without using a solenoid control valve. The mini power pack units are small HPU’s that appear slightly larger than the micropower pack units and are suitable for mobile applications. The HPU‘s that are suitable for industrial applications, mainly for in-plant operations are called standard hydraulic power pack units. Such standard HPU‘s are suitable for handling large-scale operations with heavy load and pressure ratings. The hydraulic power unit stations are considerly larger in size and are designed for specific applications.

How to choose the right hydraulic power pack suitable for your application? The HPU specifications that need to be considered are flow rate, working pressure, motor power, hydraulic oil type, reservoir capacity and more. It is also necessary to understand how often you use the application and whether it causes any system failure or not. Similar to all other hydraulic systems, the HPU also requires proper maintenance to improve its performance and life. As a part of maintenance, the HPU needs to be monitored regularly for understanding leakage, overheating, over pressure and other related problems.

Post time: Jul-21-2022