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Controlling Varnish in Your Compressor

Controlling Varnish in Your Compressor


Varnish is something that is an antagonist to all compressor gearcases. How is varnish formed, and what causes it to coat bearings; more importantly, what can you do to prevent it?

What Causes Varnish Buildup?

A driving factor behind varnish buildup lies within an unclean, unmaintained compressed air system. A unit that hasn’t followed regularly scheduled maintenance will create a perfect environment for particulates, such as dirt or rust, to enter and mix with the lubricant. These particulates will saturate the compressor oil, which leads to varnish within the system. Filters that have not been regularly replaced are a prime example of where this dirt could be coming from. Any compound that can add as an oxidizing agent can contribute to the creation of varnish.

The quality of lubricant that is being used can also contribute to varnish buildup. Mineral oil and PAG (polyalkylene glycol) lubricants are prone to oxidation, are less stable under high temperatures reducing viscosity, and offer less protection for metal components of the air compressor. These lubricants also provide less protection against rust, corrosion, and varnish.  

One important factor mentioned above that affects varnish is heat. The higher the temperature, the more it will raise oil oxidation levels (this is where oxygen and oil molecules collide). In fact, every 10°C (18°F) increase in the oil’s operating temperature will see the rate of oil oxidation doubled. Alongside this, for every 10°F over design operating temperature, the operating service of the lubricant will be cut in half. These higher temperatures are often unavoidable when operating air compressors, which is why choosing a high-quality lubricant that is specifically designed for higher heat tolerance is essential to fighting varnish.

What Steps Can You Take In Preventing Varnish Buildup?

Luckily, preventative measures can be taken to reduce the amount of possible varnish buildup within your air compressor! One is to follow regularly scheduled maintenance guidelines consisting of inspections, cleaning, replacement of filters, and overall maintenance to diminish excess particulates and dirt from contaminating the lubricant. 

Testing lubricant each quarter is a crucial maintenance routine. By regularly analyzing the fluids in your compressor, you will gain valuable insight into the overall health of your unit. For this reason, FS-Elliott’s warranty programs, SteadiAIRTM 5 and SteadiAIREND 3 require quarterly fluid analysis on each unit to ensure that each air compressor is running as efficiently as possible.

If an air compressor is already contaminated and showing signs of varnish, the best solution is to utilize a cleaning solution like our TurboCoolTM CC cleaner. TurboCool CC helps to remove the current varnish in your compressor. Click here to find out how TurboCool CC can help clean an aging compressor.

When it comes to preventing or reducing varnish, using a high-quality lubricant such as TurboCool along with performing the regularly scheduled maintenance checks within your compressor are the two most prominent actions you can take. Since TurboCool is a full synthetic and oxidative resistant, it prevents fluids from becoming thicker and resists the buildup of carbon deposits on rotating components within the compressor. 

As always, if you have any questions regarding varnish, lubrication, or anything related to your compressor, please reach out to your authorized FS-Elliott Channel Partner.

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