Oxidation Fundamentals and Its Application to Turbine Oil Testing

The current turbine oil oxidation bench tests have been in place for many years. Recently, however, the basestocks used to formulate these lubricants have changed significantly. Traditional basestocks, containing high levels of aromatics and sulfur, have been substantially displaced by more highly refined basestocks, which have very low levels of aromatics and almost no sulfur. Over time it has become clear that the oxidation performance of the different basestock classes is quite different. One key question, however, remains unanswered. “What modifications are required in current bench tests to adequately mimic oxidation processes in modern turbine lubricants?” In order to adequately address this critical question, the fundamentals of lubricant oxidation and stabilization will be discussed. Data will be presented on the oxidation of different basestocks under varying conditions of temperature, metal catalysts and antioxidant type, using model bulk oil oxidation tests. The data highlights the fundamental oxidation mechanisms that can occur in turbine oil systems and new test methods are proposed.