Matej Kunavar, dipl. inž., Kolektor ETRA, d. o. o., Ljubljana – Črnuče;
Nejc Novak, mag. inž., doc. dr. Franc Majdič, univ. dipl. inž., oba Univerza v Ljubljani, Fakulteta za strojništvo

Abstract:
In the first part of the paper, the reasons for the appearance of particles inside the hydraulic liquid are presented. These are the four possible types of wear, two-body abrasive wear, three-body abrasive wear, erosion and cavitation. The newly formed particles migrate through the hydraulic fluid and further increase the wear. Filtration is therefore essential.

Test powder is expected to be used in standardized tests, but it is very abrasive to hydraulic components.

The aim of the present work was to show the difference between the standardized test powder and the actual particles present in the hydraulic fluid of an industrial plant.

We have developed a method to sample particles from a clogged hydraulic filter of SIJ iron plant Acroni Jesenice. Cut the filter material into smaller pieces, place it in a test tube, and rinse it with cleaning alcohol. If clean particles remain at the bottom of the tube, dry them and prepare them for observation on an optical and electron microscope.

The continuation of the article will appear in the next issue of Ventil magazine. In the second part, we will present the process of analyzing particle samples obtained from an industrial filter. We will show their shapes and material and compare them with standard test powder.

Key words:
hydraulics, hydraulic fluids, filtration, cleanliness, particles, wear, microscopy