Microdieseling occurs due to an implosion of entrained air bubbles that cause localized temperatures to spike - some as high as 1,800 degrees F. This high temperature actually cracks the oil, generating auto-oxidation and creating varnish.
Additive System Game Plan
Recently, a third strategy has been developed that can now be incorporated into maintenance professionals’ preventive programs. An additive system has been developed that actually keeps varnish from forming on metal components of hydraulic systems.
Fully-formulated anti-wear additive systems, such as Schaeffer Manufacturing’s VarniShield, combine carefully-selected additives to prevent the formation of varnish. Much like the additives in engine oil prevent the formation of sludge, these anti-varnish additive systems disperse and suspend varnish precursors and varnish as they are formed, thereby allowing the correctly sized filter to remove these deposits.
With any additives, the treated fluid should be closely monitored for oxidation during service life. Tests such as TAN (Total Acid Number), Varnish Potential, RULER (Remaining Useful Life Evaluation Routine) method or the FTIR (Fourier Transform Infrared spectroscopy) method will indicate the health of the hydraulic system. These test results need to be trended over time, as a snapshot or a single sample does not give the true picture of the system’s health.
Big or small, any hydraulic system can fall victim to varnish formation. Knowing how to evaluate the symptoms is key to identifying varnish development.
The best defense, however, is preventing varnish from forming in the first place.
Jim Carroll is vice president of technical services for Schaeffer Manufacturing (www.schaefferoil.com). Based in St. Louis, MO, it specializes in developing quality lubricants, fuel additives and chemicals for vehicles used in the mining, construction, trucking, marine and farming industries, as well as specialized lubricants and metalworking fluids for all types of machinery and equipment. Carroll holds a Certified Lubrication Specialist (CLS) from the Society of Tribologists and Lubrication Engineers (STLE) and is a retired Colonel in the U. S. Army Reserve with three deployments to the Middle East, all dealing with heavy equipment maintenance.