Is Air a Contaminant?

When we think of contamination in lubricated systems, we often focus on particle and water contamination. The fact of the matter is that there are many other contaminants we should consider and attempt to control. Most contaminants, which include any material not contained in the lubricant's formulation, can potentially damage the oil and the lubricated components. Although air is always present in lubricating oil, it is often justifiable to adopt measures to minimize its presence.
Air can exist in oil in three different states: dissolved, entrained and foam. Air dissolved in oil exists as individual molecules which are similar to CO2 dissolved in soda water. This type of air is invisible and impractical to detect. Entrained air in oil is comprised of tiny air bubbles suspended in the oil. This type of air contamination is arguably the most damaging, and can be identified by the oil having a cloudy appearance. Although there are several common causes for cloudy oil, this can be identified by taking a sample of the oil and observing whether or not it clears up over time.
If the cloudiness was caused by water or another liquid contaminant, an aqueous layer should form as the sample clears. Foam is the other common type of air in oil. Foam typically refers to the stable layer of relatively large bubbles that accumulate at the surface of a reservoir. In some systems, foam at the surface may not cause a lot of damage, but the presence of a foam layer normally indicates extensive air entrainment.


With Regards,

Sebastian

G.M. Technical

Nunes Instruments

645 Hundred Feet Road,

Coimbatore. 641012.

Tamil Nadu

India,

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