Hydraulic power units provide pressurized flow to hydraulic motors, cylinders, and other hydraulic components. Hydraulic power units (HPUs) differ from pumps, as an HPU contains a fluid reservoir, multiple pump stages and coolers to keep fluid at a safe working temperature. Performance specifications, physical characteristics, and features are all important parameters to consider when searching for hydraulic power units.

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Performance Specifications

Performance specifications to consider when selecting hydraulic power units include operating pressure, flow, total power, and reservoir capacity.

The operating pressure is the pressure the power unit can deliver at the outlet. The power unit may be expressed as a single pressure rating, or it can be rated to operate over a range of pressure.

The fluid flow through the power unit may be a single rating, or have low and high rating points.

The total amount of power the motor / pump can draw or is rated to operate. Some power units have multiple power sources, and this specification is the power available from all sources. Power is measured in horsepower, or similar units.

The capacity of the power unit reservoir is measured in gallons or similar units. Some units may have interchangeable or modular reservoirs with a range of capacities.

Physical Specifications

Physical specifications to consider for hydraulic power units include the pump type, power source, cooling method, and unit weight.

All hydraulic power units have some type of integrated pump. Some units are available with multi-stage pumps, which perform like multiple pumps connected in series. Pump types available for hydraulic power units include single stage, double stage, three or more pump stages, and multiple pump units.

Power sources include electric motor, diesel engine, gasoline engine, and pneumatic compressor.

The cooling method can be none, heat exchanger, or fan-driven oil cooler.

The unit weight is also important to consider.

Standards

SAE J1689 - Hydraulic power units used on machine tools and equipment for the automotive industry.

SAE ARP1280 - Aerospace - application guide for hydraulic power transfer units.

References

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Griffin Pump & Equipment, Inc. | CS UNITEC | Alcoa Fastening Systems