Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/1399684
18 | July - August 2021 | www . machinerylubrication.com Complete Guide to Lubricant Deposit Characterization Dave Wooton, PhD, Wooton-Consulting | Greg Livingstone, Fluitec, International OIL ANALYSIS e current practice for the users of industrial lubricants has been to assume that all deposits or varnishes are created equal. One tends to look at the color of a deposit and assume that, since it is brown, it must be the same as the brown sample previously observed. is assumption can be far from correct and can lead to taking the wrong corrective actions. ere are many chemistry types in varnish materials. When one thinks of sludge or varnish, the concept needs to be broadened. is material is not simply the oxidation or degradation products from the lubricant — more generally, it is the material coming out of the fluid with the potential to cause operational issues. Equipment reliability issues are not only caused by fluid degradation and varnish deposits but by any mate- rial that is not a homogenous single phase with the lubricant. erefore, any foreign material causing deposits in the lubricant can potentially be defined in this category. Deposit Characterization Process e characterization of deposits becomes the path toward the root cause of its formation. ere are a wide variety of testing technologies available for determining the chem- istry of the deposits. However, it is sometimes challenging for opera- tional plants to obtain samples of deposits to allow for these analyses. It is much easier to get a sample of the in-service lubricant. In this case, the first step is separating the oil degradation products believed to be responsible for generating the deposits from in-service oil samples. e separation step developed can be accomplished physically, mechani- cally or chemically. e next step is to determine the organic and inorganic composition of the deposit. Two useful tests for analyzing the lubricant are elemental spectroscopy and Fourier Trans- form Infrared spectroscopy (FTIR). Common deposit characterization tests used in these studies are FTIR and X-ray Florescence spectros- copy (XRF). ese results are then compared to provide a chemical characterization of the deposit, as well as allow for a possible root cause, to be determined. ese steps are presented in Fig. 1. " One tends to look at the color of a deposit and assume that, since it is brown, it must be the same as the brown sample previously observed."