Abstract
PurposeApart from the basic material properties of liquid lubricants, such as, e.g., the viscosity and density of the hydraulic fluid, it is also important to have information regarding the electrical properties of the fluid used. The latter is closely related to the purpose, type, structure, and conditions of use of a hydraulic system, especially the powertrain design and fluid condition monitoring. The insulating capacity of the hydraulic fluid is important in cases where the electric motor of the pump is immersed in the fluid. In other cases, on the basis of changing the electrical conductive properties of the hydraulic fluid, we can refer its condition, and, on this basis, the degree of degradation.Design/methodology/approachThe paper first highlights the importance of knowing the electrical properties of hydraulic fluids and then aims to compare these properties, such as the breakdown voltage of commonly used hydraulic mineral oils and newer ionic fluids suitable for use as hydraulic fluids.FindingsKnowledge of this property is crucial for the design approach of modern hydraulic compact power packs. In the following, the emphasis is on the more advanced use of known electrical quantities, such as electrical conductivity and the dielectric constant of a liquid.Originality/valueBased on the changes in these quantities, we have the possibility of real-time monitoring the hydraulic fluid condition, on the basis of which we judge the degree of fluid degradation and its suitability for further use.
Highlights
Good knowledge of the physico-chemical properties of hydraulic fluid is a prerequisite for the correct, long-term, economically and environmentally sustainable use of the fluid built into a hydraulic system
On the basis of known electrical values, we can decide on the design of the hydraulic unit, or on the basis of changing electrical values, we can conclude on the state of the installed fluid (Ticand Lovrec, 2017; Carey and Hayzen, 2001)
Accurate absolute values of the dielectric constant and electric conductivity for the concerned mineral hydraulic oil were first measured with a precise laboratory device and, in the step, the on-line sensors were calibrated to the determined values
Summary
Good knowledge of the physico-chemical properties of hydraulic fluid is a prerequisite for the correct, long-term, economically and environmentally sustainable use of the fluid built into a hydraulic system. Less in use fluid acidity monitoring, FTIR analysis and wear particle analysis are used for more detailed condition analyses. These are more limited to laboratory tests. On the other hand, knowing and monitoring the changes in the electrical values such as dielectric constant and electric conductivity of a hydraulic fluid provides a more detailed insight into the physical and chemical condition of the fluid, its degree of degradation and the prediction of the remaining service life (Meindorf, 2005). The authors are thankful to all colleagues in both companies who provided their expertise and skills that assisted this study greatly
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