Is a hydraulic power unit a pump?

To put it bluntly: not exactly.
Although many people easily confuse the two, from a professional perspective, a hydraulic pump is only a core component within a hydraulic power unit.
You can understand it this way: if you compare a hydraulic system to a car, the hydraulic pump is like the "engine block," while the hydraulic power unit is the entire "engine," including the oil tank, lines, switches, and all the supporting facilities that make the system work.

Here's a detailed breakdown of their relationship:

1. Inclusion Relationship: One is a "part," the other is a "system"

Hydraulic pump: It is an independent mechanical component, mainly responsible for drawing in and pumping out oil. It cannot work on its own; someone must rotate its shaft.
Hydraulic power unit (HPU): This is a complete package. When you buy a hydraulic power unit, you get a power source that you can take home and connect the pipes to, and it already has a hydraulic pump installed.

2. Structural Differences: What does an HPU have that a pump doesn't?

A complete hydraulic power unit, in addition to the pump, also comes with many "accessories":
Power source: It usually comes with an electric motor or gasoline engine to drive the pump.
Reservoir (oil tank): The pump itself doesn't store oil, but the power unit has a large oil tank below it to store and cool the hydraulic oil.
Control center (valve block): The power unit is equipped with directional valves and pressure valves, which determine where the oil flows and how much pressure is applied.
Protector (filter): It also comes with a filter to ensure that the circulating oil is clean.

3. Functional Division of Labor

The function of a hydraulic pump is very simple: it only generates flow. If you only buy a pump, you still have to find a motor to drive it, weld an oil tank to hold the oil, and configure valves to control the pressure.
The function of an HPU is comprehensive: it is responsible for the entire process from oil suction, pressurization, pressure regulation, impurity filtration, to heat dissipation. It is the "backstage manager" of the hydraulic system.

4. A simple analogy

A hydraulic pump is like a "water pump head."
A hydraulic power unit (HPU) is like a complete "car wash machine." The car wash machine does indeed have a pump head, but it also includes a casing, wires, a switch, a water tank, and a spray gun.

5. Why do people often confuse them?

On construction sites or in workshops, to save time, people sometimes point to the buzzing square box and say, "The pump is broken," when they actually mean the entire hydraulic power unit has stopped working. However, when buying parts or performing repairs, it's crucial to distinguish between the two:
If the pump is broken, you only need to replace the rotating component inside.
If the entire power source is malfunctioning, it might involve a burnt-out motor or a leaking oil tank.