An Overview of Progress and New Developments in FTIR Lubricant Condition Monitoring Methodology

Fourier transform infrared FTIR spectroscopy has found an important analytical niche in the field of condition monitoring CM of lubricants, lubricant quality being a primary determinant of the wear and operational efficiency of engines and machinery. The ability to track a wide range of functional groups associated with chemical changes in lubricants by FTIR spectroscopy allows the overall quality of lubricants to be assessed and informed decisions made as to whether a lubricant needs to be replaced or not. Newer automated FTIR systems in centralized laboratories are now capable of analyzing oil samples at rates of 120 samples/h, providing trending information on soot, moisture, glycol, oxidative status, anti-wear additives, and nitration, amongst other measures. The current FTIR CM methodology is based on ASTM Standard Practice E2412-10 and is restricted primarily to petroleum or mineral oils; however, the ability to spectrally classify oils could overcome this limitation and broaden the scope of the methodology substantially. Quantitative FTIR methods have come to the fore to carry out more specific measures related to oil condition, specifically the determination of acid content and base content, as well as moisture. These methods have been designed to overcome some key limitations associated with the corresponding ASTM titrimetric procedures and expand the overall utility of FTIR instrumentation in centralized lubricant analysis laboratories. This paper provides an overview of FTIR CM, how it has been and can be further improved, and discusses the recent advances in the newer quantitative FTIR CM methods as well as the issues that need to be addressed to further enhance the utility of FTIR spectroscopy in relation to lubricant analysis.