Standard for evaluating filtration performance of a filter element in hydraulic systems (ISO 16889:2008(E)) defines preparation of a suspension of hydraulic oil and test dust for use in the test system. First the suspension needs to be mechanically agitated and then treated with ultrasound for elimination of potential agglomerates. Standard only defines power density of ultrasound , which needs to be between 3000 Wm-2 and 10000 Wm-2. Other parameters of a mixing process are not determined. Using commercially available hand blender and ultrasonic bath we met the conditions stated in standard and prepared suspension. At various mixing times we analyzed samples of suspension using microscope and computer program. We tried to determine the suitability of the preparing method of suspension. Results have shown that suspension in analyzed volume is suitable and that use of a rotor - stator mixer and ultrasonic bath is effective. Suitability of the whole volume of a suspension could not be determined.
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