The acid number and base number of in-service oils are considered key indicators of oil quality and are used to monitor the accumulation of acid and the depletion of the base additive package. A significant rise in acid number or decrease in base number may reflect deterioration in oil quality either due to chemical reactions, oxidation, incorrect oils, additive depletion or contamination.
ASTM methods, including D664, D974, D2896 and D4739, are the current industry standard methods for measuring the acid and base number. These titration-based methods are slow and expensive to execute, require significant volumes of sample and solvent, and are prone to interferences. As a result, these methods have relatively wide repeatability and reproducibility limits, accounting for their significant inter-laboratory variability. The high cost and poor accuracy of these methods limit their usefulness and application to routine oil monitoring.
Craig Winterfield, and Frederik van de Voort, in cooperation with Thermal-Lube have developed an innovative new mixed-mode FTIR calibration used to accurately predict acid and base numbers with throughputs of up to 60 samples per hour and using significantly less sample and reagent volumes. The result is that FTIR users can benefit from less capital investment, less startup and maintenance time, more productivity and have less environmentally sensitive waste to dispose of.