COMPARING DIFFERENT ANALYTICAL TECHNIQUES TO MONITOR LUBRICATINGGREASE DEGRADATION

摘要

During lubricant operation temperature, pressure and load are well known as the main factorsenhancing degradation. To monitor this degradation process in lubricating oils, the industry has definedspecific test methods involving correct sampling techniques and analytical techniques to provide efficientinformation on the correct oil change interval. Moreover, modern oil-lubricated systems apply specific oilmonitoring procedures as part of condition based maintenance practices to detect root cause failuresand prevent equipment damage (1)(2).Applying these condition monitoring practices on lubricating greases is much more complex as oncethese greases are put into service, it becomes rather difficult for end-users to perform on-site greasecondition monitoring, and define the correct frequency for re-greasing bearings. This explains whyindustry relies for grease-lubricated systems procedures on time-based intervals (preventivemaintenance). In this study, work has been done using greases primarily based on mineral oil with alithium soap thickener.The grease was oxidized to produce samples at different intervals in order to evaluate differentanalytical techniques. More specifically: Acid Number (AN), LSV (linear sweep voltammetry - RULER)and FTIR tests were done on the grease and on its corresponding oil tests such as viscosity, ICP andDSC were performed. Besides the maximum information that each selected analytical techniques shouldcould provide on the grease condition, the program was also used to evaluate the minimum quantity ofsample required, time taken as well as the cost of analysis.