Design of hydraulic power packs
TFS expertise in hydraulic power units
A hydraulic power pack (also called a hydraulic power unit, or HPU) is the assembly that generates and regulates the fluid power of a system: it converts electrical or thermal energy into pressure and flow, and delivers it to the machine actuators. It is the heart of every hydraulic system.
How a hydraulic power pack works
The operation of a hydraulic power unit follows four steps. The motor (electric or combustion) drives the pump; the pump draws oil from the reservoir and pressurises it, generating the required flow; the control valves regulate pressure, flow rate and flow direction towards the actuators (cylinders or hydraulic motors); the return oil flows back into the reservoir through the filters and, where fitted, the heat exchanger. The power pack does not produce motion by itself: it supplies the hydraulic energy that the machine cylinders and motors convert into work.
Hydraulic power pack diagram: the components
The layout of a hydraulic power unit typically comprises the following elements, each to be sized according to the duty cycle:
- Motor — constant-speed electric motor or, on mobile and emergency systems, a combustion engine
- Pump — gear, vane or piston type, fixed or variable displacement depending on the required flow profile
- Reservoir — sized for settling, heat dissipation and air separation, with supply and return lines
- Filtration — pressure, return and breather filters, to maintain the contamination class required by the components
- Control valves — pressure relief, flow control, directional valves, proportional valves or servo valves
- Distribution manifold — the block that collects and routes the lines to the consumers
- Heat exchanger and instrumentation — oil cooling, pressure gauges, pressure switches, thermostats, level sensors
Custom power pack or standard unit?
For standard applications there are compact off-the-shelf power packs — such as the ABPAC units by Bosch Rexroth, pre-configured power units covering the most common power ratings and flow rates with short lead times. They are the right choice when the duty cycle falls within the catalogue sizes.
A custom hydraulic power pack — a dedicated hydraulic power unit — becomes necessary when constraints arise that the standard product does not cover: envelope and layout dictated by the machine, cycles with multiple consumers at different pressures, noise requirements, strict filtration classes, sector certifications (marine, ATEX, fire-fighting), or the integration of electronic control and remote diagnostics. In these cases TFS designs the unit starting from the actual duty cycle, not from a predefined size.
Sizing: the parameters that matter
Design always starts from the application data: maximum and working pressure, flow rate required by the consumers and their simultaneity, duty cycle (continuous or intermittent) and the resulting thermal balance, fluid used and contamination class permitted by the components, available space and installation constraints, available electrical supply. An undersized reservoir or heat exchanger is among the most frequent causes of premature oil degradation and pump failure.
Service and maintenance of hydraulic power units
A well-designed power pack still needs to be maintained: servicing of hydraulic power units covers oil analysis and replacement, filter element changes, verification of pressure settings, condition checks on pumps and valves, accumulator recharging and diagnosis of thermal anomalies. TFS works both on power packs it has built and on units from other manufacturers, with scheduled maintenance agreed around the customer production cycle, on-site support, and repair or overhaul of components on the Bosch Rexroth certified test bench.
TFS expertise
TFS designs and manufactures custom power packs for every sector — industrial, marine, presses, steel, oil & gas, hydroelectric — selecting the optimal components among its partner brands and integrating filtration, cooling and electronic control. As a Bosch Rexroth Certified Excellence Partner in the Distribution, Solution and Service areas, TFS covers the whole cycle: design, manufacturing, commissioning, testing and service.
TFS technologies and services involved
Do you have a hydraulic project to tackle?
Tell us about your needs: the TFS technical team is here to help.
Contact us →