top of page

Varnish Removal Services


Lubricant varnish has become a significant maintenance problem in many critical hydraulic and lubrication oil applications, such as gas turbines, paper machines and compressors. Turbine oil varnish has been a particularly high profile issue over the last decade. A very small amount of varnish that settles in a susceptible zone, such as a fuel control or IGV valve, can prevent the system from starting properly, resulting in a fail-to-start condition or in some cases a unit trip.



  1. Decrease the effectiveness of heat exchangers, making it more difficult to control fluid temperature.

  2. Increase the wear rates of valve components, load gears, and in some cases, bearing surfaces.

  3. Shorten the lubricant’s life by reacting with the anti-oxidant system

  4. Cause premature filter change-outs and oil flow restrictions

  5. Reduce seal life and increase oil leakage


varnish removal service
Field Services - varnish removal

When varnish contamination is severe and causing operational issues (stuck servo-valves, high bearing temperatures, etc.) a “Varnish Flush” is often the only way to bring a hydraulic or lube oil system back to “like new” cleanliness conditions.


OFS has both the equipment and the experience needed to quickly remove varnish that has plated out on the metal surfaces within a hydraulic or lube oil system. 


An appropriate “system cleaner” is typically mixed with the oil to act as a solvent to break up solid deposits that have accumulated in the piping and reservoir, and after recirculation within the system for a period of time, the contaminated oil/solvent mixture is eventually drained out of the system and disposed of.  Depending on several factors, a “scavenging” oil is sometimes used to rinse the system, and a new fill of filtered oil is then pumped into the system. 


After a “Varnish Flush” has been performed, OFS can then provide a Varnish Removal System that continually recirculates the oil and prevents varnish from accumulating in the system over time. 


OFS will work with your team to develop a custom Flush Plan that best suits your application, time-line, and budget.

Varnish Removal In Solar Titan 130 Gas Turbine

Maintenance personnel at the Power House of a major university in New York noticed discoloration of the Mobil SHC 32 Lube Oil in their Solar Titan 130 Gas Turbine Generator after several years of operation. This prompted them to conduct oil analysis, and the lab results revealed an elevated varnish potential number of MPC 53. If left untreated, operators were worried that varnish would eventually plate out on the metal surfaces within the lube oil system, causing elevated bearing temperatures and possible premature wear and failure.

Read the full case study here.

Varnish Contamination in Hydraulic & Lube Oil Systems

Varnish is a soluble and insoluble contaminant made up of by-products of oil degradation. It can appear as a sticky or gel-like substance in the oil, or which plates out on the metal surfaces of lube systems. This can cause ‘stiction’ on servo-valves, and it can affect clearances and tolerances in bearings and hydraulic control systems. As oil degrades, waste by-products from the additive package are formed, thus creating varnish. This is commonly observed in hydraulic components, in - side engine rocker covers, and on journal bearings.

Read the full case study here.

bottom of page