Hydraulic Powerpack Design Considerations

Hydraulic power packs are the very heart of your hydraulic circuit, so they need to be designed correctly.

Hydraulic power packs come in many different shapes and sizes; from very large (and generally stationary) industrial units through too much smaller and compact packs designed for mobile applications. To ensure your power pack provides consistent and reliable performance, we first need to understand the application in which it will be used.

The following elements will all have an influence on the final power pack design: Operating Environment (ambient temperature) The number of cycles performed by the actuator/motor, pressure, and flow requirements and finally, availability of a suitable power source for the primary driver (Electrical Motor or Engine)

The key elements for the Hydraulic Power Pack are described below

Oil Reservoir

The hydraulic fluid reservoir holds excess hydraulic fluid to accommodate volume changes from: cylinder extension and contraction, temperature driven expansion and contraction, and leaks. The reservoir is also designed to aid in separation of air from the fluid and work as a heat accumulator to cover losses in the system when peak power is used.

Design engineers are always pressured to reduce the size of hydraulic reservoirs, while equipment operators always appreciate larger reservoirs. Reservoirs can also help separate dirt and other particulate from the oil, as the particulate will generally settle to the bottom of the tank. Some designs include dynamic flow channels on the fluids return path that allow for a smaller reservoir.

View our range of oil reservoirs here.

Primary Driver

The primary driver is the component that will drive the hydraulic pump and in turn, develop a flow of hydraulic oil. Choice of primary driver will be dictated by the application in which the hydraulic power pack is used.  For mobile applications, typically we utilise the combusion enginer output due to a lack of available electric power. Industrial power pack applications generally utilise electrical motors as their primary drivers. Electric motors provide instant torque, smooth running and quiet operation. 

 All primary drivers must be sized specifically for the power pack application; it will be their job to provide sufficient horsepower to drive a hydraulic pump capable of delivering the required flow and pressure for the hydraulic circuit.

To calculate the size of the primary mover (typically an electric motor or engine), we must first establish the size of the hydraulic pump to give the required flow for the system. Once we have sized the pump, we then know the power required to drive the pump and specify the correct size motor or engine.

View our range of electric motors here. 

Hydraulic Pump

The choice of Hydraulic Pump will depend on various factors including, pressure, flow, and duration of cycle. A simple fixed displacement gear pump can be utilised for applications that require a constant flow and pressure (driving a hydraulic motor at a fixed speed for example)

Pressure compensated pumps provide a greater level of efficiency by providing pressure only when required. These pumps are generally more expensive but will give improved performance. Using a variable-displacement, pressure-compensated pump rather than a fixed-displacement pump reduces circuit horsepower requirements dramatically.

When calculating the power input to the pump, the total pump efficiency must be included. This efficiency is the product of volumetric efficiency. The average for axial piston pumps = 0.87. The formula shown on our fluid power formula page allows for an efficiency of 80%

View our range of hydraulic pumps here.

Filtration Requirements

Filter efficiency is the most important but not the only factor involved when evaluating the filter design. A filter can be ineffective if it is installed in the wrong place and if it is given the wrong job.

When creating a filtration concept, some fundamental rules play a crucial role. For example, the hydraulic filter is always to reduce wear which means it should filter to a finer level than the critical tolerances. Filters should be used with the highest possible flow rate.

Suitable seals on cylinders and on breather filters should prevent contamination from entering the system etc. Therefore, we can distinguish between protective filters and working filters.

View our range of hydraulic filters here.

If you would like to learn more about Hydraulic Power Pack solutions available from Zeus, please click here

To view the full range of standard Hydraulic Power Pack units, please click here