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1.
On-line condition monitoring and evaluation of remaining useful lifetimes for mineral hydraulic and turbine oils
Vito Tič, Darko Lovrec, 2017, scientific monograph

Abstract: Condition monitoring of hydraulic and turbine oils, and especially their remaining useful life, is becoming an important strategic business advantage for plant owners, which benefits in environment protection and cost reduction. This monograph discusses the problem of condition monitoring of hydraulic fluids throughout their life-cycles. Particular emphasis is placed on assessing mineral-based oils’ conditions and their remaining useful lifetimes quantitatively. Practicality and usefulness are vital when developing and deploying various methods for condition monitoring systems within industrial environments. Therefore, it is important to know the oil degradation mechanisms and influencing factors, commonly used laboratory methods and oil ageing tests, as well as, for on-line condition monitoring system design, the available sensors with all their characteristics and restrictions. The proposed approach is based on a novel method for testing the durability and oxidation stability of different hydraulic and turbine oils. The developed mathematical model is based on data from previously conducted oil-ageing tests for the assessment of an oil's condition and its remaining useful lifetime. The method can also be used for comparison of different oils and selection of a more adequate oil with high oxidation stability and long service-lifetime.
Keywords: Hydraulic and turbine oils, degradation mechanisms, on-line condition monitoring, test methods, remaining useful lifetime
Published: 22.12.2017; Views: 896; Downloads: 232
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2.
Phenols, proanthocyanidins, flavones and flavonols in some plant materials and their antioxidant activities
Mojca Škerget, Petra Kotnik, Majda Hadolin Kolar, Andreja Rižner Hraš, Marjana Simonič, Željko Knez, 2005, original scientific article

Abstract: Methanol extracts prepared from five plant materials native to the Mediterranean area, namely olive tree (Olea europaea) leaf, St. John's wort (Hypericum perforatum), hawthorn (Crataegus laevigata), oregano (Origanum vulgare) and laurel leaf (Lauris nobilis), were examined for their phenolic components. Total phenolic content was determined by the Folin-Ciocalteu method. The content of proanthocyanidins in acid-hydrolysed extracts was determined spectrophotometrically. The contents of free flavones (apigenin andluteolin) and flavonols (kaempferol, myricetin and quercetin) were determined by HPLC analysis. The time of hydrolysis of flavones, flavonols andproanthocyanidins was optimised. Antioxidant activities of apigenin, luteolin, kaempferol, myricetin, quercetin and of plant extracts were examined. Antioxidative activities were studied in sunflower oil at 98 °C, by measuring peroxide value, and in an aqueous emulsion system of -carotene and linoleic acid by measuring the absorbance of the sample. Among flavones and flavonols investigated, only myricetin inhibited oxidation of sunflower oil. All other flavones and flavonols showed pro-oxidative activity. Oppositely, in the emulsion system, only apigenin showed pro-oxidative activity while otherflavones and flavonols and plant extracts inhibited oxidation of -carotene.
Keywords: chemical processing, extraction, plant material, fenolic content, hidrolysis, antioxidants, flavones, flavonols, proanthocyanidines, oils, emulsions
Published: 01.06.2012; Views: 1628; Downloads: 87
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3.
Concentration of free fatty acids in rapeseed oil
Petra Kotnik, Mojca Škerget, Željko Knez, 2012, published scientific conference contribution

Keywords: materials, methods, vegetable oils
Published: 01.06.2012; Views: 1298; Downloads: 17
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