Technical Cleanliness of Assembled Fluid Power Components

The demands on the cleanliness of fluid power systems increase continuously. The KompuNW project, which was launched in 2011, aimed to find out the technical cleanliness of fluid power components in Finland, and the technical cleanliness was measured with commercial cleanliness cabinets. These cabinets apply well for hydraulic components where a rinsing pen should reach the test component surfaces that need to be controlled. In some cases the flow rate or the pressure produced by the cleanliness cabinets is insufficient for detaching particles from the surfaces of hollow components e.g. hydraulic cylinders or oil reservoirs. For this reason the functional test bench, designed and constructed in IHA, uses low viscosity hydraulic oil to extract contaminants from the assembled fluid power components. The extracted particles can then be analysed in the test bench with a microscope or an inline particle counter. This paper has several aims. First the backgrounds of fluid power components are described. Then this paper will present the differences in the definitions and codes of oil cleanliness (ISO 4406:1999, SAE AS4059E:2005) and component cleanliness (ISO 16232:2007). In addition, the differences between the test bench and the commercial cleanliness cabinets are presented. Standards ISO 16232:2007-5 and ISO 18413:2002 were applied in the design of the test bench. The main points of these standards are introduced in this paper, too. Finally the extraction procedures of a hydraulic cylinder and oil reservoir are shown with examples of the extraction curves of these components.