By Jim Fitch
Machinery Lubrication Magazine
The approach of detecting and analyzing sludge and varnish problems in machinery is not the same as used oil analysis. In many instances this is because the evidence is not always in the oil. The sludge and varnish should be analyzed directly, using a completely different set of tests and evaluation parameters. Still, used oil analysis plays an important diagnostic role to help reveal candidate causes as well as to rule-out others.
The conditions that commonly lead to sludge and varnish problems vary, which complicates the process of identifying the root cause analytically. There are at least 25 unique lubricant degradation mechanisms leading to sludge or varnish formation.