The importance of oxidation-resistant turbine oils in the various applications in which turbines are used is difficult to understate. Turbines in themselves are very costly energy-converting mechanisms which, among many other applications, provide much of the electricity for the power grids of modern society. Most critical to these turbines are the lubricants that are essential to their operation in long, dependable service. Equally critical, then, are the tests that determine the acceptability of these turbine oils and the understanding of the oxidation mechanisms that cause these oils to form deposits and otherwise lose their ability to properly lubricate the turbine. This paper is a first report on a new dry-bath approach to not only determine antioxidation characteristics of turbine oils in the well-known Rotating Pressure Vessel Oxidation Test (RPVOT) but to enable the direct study and modification of the oxidation process as it occurs. The instrument not only eliminates the hot oil-bath associated with the RPVOT but also allows the test fluid to be available for direct monitoring of temperature, chemical content, and the effects of injecting reactants. In the process of gathering the preliminary information for this paper, it was found that significant exotherms may develop in the turbine oil at a critical stage of oxidation response. These exotherms can vary in duration and temperature rise depending on the nature of the antioxidant system and other properties of the formulated turbine oil. Moreover, the fact that these exotherms seem to mark a certain level of the oxidation process, brings the opportunity to more thoroughly investigate and understand oxidation processes as well as the chemistries of other lubricants.

Four turbine oils formulated with varying types and concentrations of antioxidants were aged via D 943 exposure and examined extensively at 1000, 2000, 5000, and 10 000 h. Acid number, Rotary Pressure Vessel Oxidation Test (RPVOT), High Pressure Differential Scanning Calorimetry (HPDSC)RP, and sludge determinations were made at each time interval. Only a combined evaluation of the test results for the 10 000 h oil samples (a "Total Oxidation Products" approach) gave a reasonable estimation of the true oxidative state of the fluids. One shorter term test, ASTM D 6514, was found to give a fair prediction of the overall quality of the fluids at 10 000 h.

Four turbine oils formulated with varying types and concentrations of antioxidants were aged via D 943 exposure and examined extensively at 1000, 2000, 5000, and 10 000 h. Acid number, Rotary Pressure Vessel Oxidation Test (RPVOT), High Pressure Differential Scanning Calorimetry (HPDSC)RP, and sludge determinations were made at each time interval. Only a combined evaluation of the test results for the 10 000 h oil samples (a "Total Oxidation Products" approach) gave a reasonable estimation of the true oxidative state of the fluids. One shorter term test, ASTM D 6514, was found to give a fair prediction of the overall quality of the fluids at 10 000 h.

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.

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.