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DIN Standards Committee Materials Testing

Overview

This document has been prepared by Working Committee NA 062-06-52 AA "Schmierfette: Anforderungen und Prüfung" ("Lubricating greases: requirements and testing") at Technical Committee "Mineralöl- und Brennstoffnormung (FAM)" ("Standardization of mineral oils and combustible materials") at DIN Standards Committee Materials Testing (NMP). This document specifies a method for the accelerated determination of the Arrhenius activation energy of the thermo-oxidative degradation of lubricating greases in contact with catalytically active metallic materials and catalytically inactive glass. Knowledge of the Arrhenius activation energy is a prerequisite for the targeted determination of the grease service life under known temperature conditions of an application. The complete consumption of antioxidants in the lubricating grease is used to determine the activation energy. This is determined from the pressure curve during the measurement. The calculation of the Arrhenius activation energy is based on the determination of the oxidation induction time. The precision specification of the Arrhenius activation energy is limited, as a ring test to determine the precision of the oxidation induction time (OIT) has only been carried out for one temperature (150 °C). However, studies have shown that the precision of the OIT is relatively constant over the range considered from 130 °C to 160 °C, so that it can be assumed as a first approximation that the precision of the oxidation induction time is the determining factor. Detailed results of a laboratory study with different measurement temperatures can be found in an annex to the document.

Responsible national committee

NA 062-06-52 AA - Lubricating greases: requirements and testing