What is HPU in hydraulics?

In the hydraulics industry, HPU is an abbreviation for Hydraulic Power Unit.
If you consider a hydraulic machine as a car, then the hydraulic power unit is the combination of the car's "engine" and "fuel tank." It doesn't perform the work directly (it doesn't push, pull, or rotate), but it is responsible for continuously supplying energy to the working components.

1. Its Role: Energy Supply Station

In a hydraulic system, cylinders (for extension and retraction) or motors (for rotation) alone are not enough; they need pressurized oil to operate. The task of the hydraulic power unit (HPU) is to convert ordinary electrical or mechanical energy into this pressurized "power oil."

2. What "Components" Does It Consist Of?

A standard hydraulic power unit usually consists of several key parts:

Oil Reservoir:

 A large metal box used to store hydraulic oil, ensuring that the system always has oil available and also helping to dissipate heat from the oil.

Drive Motor:

This is the "power source" of the entire unit, usually an electric motor or a gasoline/diesel engine.

Hydraulic Pump:

Directly connected to the motor. When the motor rotates, the pump starts to draw in oil and pressurize it before ejecting it.

Control Valves:

Like a series of "taps," controlling where the oil flows, how much pressure it has, and when it stops.

Accessories:

Including filters (to remove impurities), pressure gauges (to show the pressure), and level indicators (to show how much oil is left).

3. How Does It Work?

The process is actually very straightforward:

Start-up:

You switch on the power, and the motor drives the pump to rotate rapidly.

Oil Suction and Pressurization:

The pump draws in cool oil from the reservoir and, through its internal structure, transforms it into high-pressure oil with immense power.

Delivery:

The high-pressure oil flows through pressure-resistant pipes to the machine parts at the other end.

Return:

After the parts have completed their work, the used oil flows back to the reservoir through another pipe, where it settles, cools down, and is filtered, waiting for the next cycle.

4. Why is it often a "square box"?

You'll find that most hydraulic power units look like a metal box with a motor attached, and this is because:
Integration: All the parts are assembled together, making them easy to move and ready to use simply by connecting the pipes.
Protection:  Enclosing the components in a box prevents dust from entering the oil and also reduces some of the noise from the motor.

5. Where are they used?

They are used whenever you need a lot of power but don't want to install a huge motor:
Road construction sites: Behind the excavator or in road paving machines.
Factory workshops: In metal stamping presses and injection molding machines.
Everyday life: Underneath the lift used to raise cars in car repair shops, you'll usually find a small hydraulic power unit.