Development of a Self-Lubricated High-Pressure Pump for Operation with Clear Water

  CAD Image of an Axial Piston Pump

The pressure range of water hydraulic systems is limited by the stress on the tribological contacts in the components. State of the art pumps reach 160 to 210 bar. Therefore, the research objective of this project was to design the contacts of a water-hydraulic pump for higher loads.

Benefit Procedure
Larger pressure range of water hydraulic systems Evaluation of pump concepts for water hydraulics
Higher power-to-weight ratio of components Construction of a simulation model for the pressure in the lubrication gap of piston shoes
Increasing the competitiveness of water hydraulic drive solutions Design of a tribological contact for lubrication with the medium water



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High Pressure in Water Hydraulic Applications

Today, water hydraulics is used in presses and mining as well as in the food and pharmaceutical industries. These applications rely on the advantages that the medium is non-flammable and non-toxic. In comparison with oil hydraulics, the pressure level is limited to 160 to 210 bar. This results from the lubrication of the tribological contacts with water.

The objective of this project was to develop a water-hydraulic high-pressure pump to increase the pressure range for applications with the medium clear water. As a result, the power density of water-hydraulic drives and the competitiveness compared to classical oil hydraulics should be increased.


Lubrication with Clear Water

Deformation of a Piston Shoe (Ansys FEM) Deformation of a Piston Shoe (Ansys FEM)

During development, the contact between piston shoe and swash plate of axial piston machines during water lubrication was observed. For the material pairings, plastics are often used whose deformation under pressure is a limitation for the pressure level. As an example, the figure shows the deformation of a piston shoe at 100 bar. The magnitude of the deformation is in the same order of magnitude as the actual gap height.

  Gap Height (left) and Leakage (right) of a Piston Shoe Gap Height (left) and Leakage (right) of a Piston Shoe

Furthermore, the deformation at higher pressures leads to an increase in the gap height, as the load-bearing capacity increases. Thus, the leakage from the sliding shoe contact also increases, in the selected example by a factor of 5 between 200 and 300 bar. This limits the maximum pressure caused by the leakage.



The research project was funded by the Federal Ministry of Economic Affairs and Climate Action with the registration number ZF4199603KO6 as a cooperation project between the Institute for Fluid Power Drives and Systems (ifas) of the RWTH Aachen University and the company Hauhinco Maschinenfabrik GmbH & Co.KG. The authors would like to thank for the support.

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Schoemacker, F., Schmitz, K.: Piston Slippers for Robust Water Hydraulic Pumps, 2018, 11th International Fluid Power Conference, Aachen