In this study we measured the remaining useful life of a wide range of turbine lubricants by detecting directly the remaining activity and performance of phenolic and amine antioxidants, known as primary antioxidants. We applied a patented (linear) voltammetric technique. First we evaluated the accuracy of the voltammetric response (vs. weight %) for phenolic (BHT) and amine (PANA) types of antioxidants. The next step of the program included antioxidant performance testing using laboratory oxidation tests. The voltammetric test data were then correlated with other widely used analytical methods (RBOT, FTIR, and DSC). These tests enabled us to understand the performance of mixed antioxidant systems and their importance in the remaining useful life of the new generation of turbine lubricants.
Finally and in order to understand the chemical role of antioxidants in real life conditions we monitored several industrial steam and gas turbine lubricants (N. America and Europe) with voltammetric analyses to observe the antioxidants' depletion trends. Voltammetric analysis correlated well with the RBOT (as per ASTM D-2272), and standard physico-chemical analysis methods (TAN, viscosity, color,...). These results show that antioxidant monitoring adds valuable information to RBOT and DSC measurements for the new type of turbine lubricants. This will allow the user to enhance the management of the oil on-site; to detect abnormal equipment/usage and consequently to improve the planning of maintenance actions resulting in a more efficient oil management.