FTIR Condition Monitoring of In-Service Lubricants: Ongoing Developments and Future Perspectives

Condition monitoring of used lubricants by Fourier transform infrared (FTIR) spectroscopy is reviewed and placed in context of the recently approved ASTM Practice E 2412-04 developed by the Joint Oil Analysis Program (JOAP) as a standardized means of trending oil/lubricant condition. A new spectral reconstitution procedure is presented and evaluated as an alternative means of executing this ASTM practice, its objective being to minimize sample handling issues associated with the high viscosity of most in-service oils. Used diesel crankcase oils were analyzed in both their neat and diluted forms in 100 and 200 μ m KCl cells, respectively, and the coefficient of variation (CV) for accuracy of the spectral reconstitution procedure was < 5% for all the parameters evaluated. Spectral reconstitution simplifies and facilitates sample handling, avoiding the need for peristaltic or syringe pumps and allowing up to 120 samples/h to be analyzed. The need for a solvent rinse between samples is also avoided, and cell clogging and tubing wear are effectively eliminated. The spectral reconstitution technique also makes the ASTM practice compatible with newer FTIR systems which are capable of quantitative determination of AN, BN, and moisture. KEY WORDS: Condition MonitoringFTIR SpectroscopySpectral ReconstitutionASTMAutomated AnalysisLubricant Analysis Review led by Cyril Migdal Notes A Reporting values in absorbance/0.1 mm.