Dissolved water is water that is completely mixed with oil at the molecular level, forming a homogeneous solution.
Unlike free or emulsified water, dissolved water does not form visible droplets and does not make the oil appear cloudy or milky.
It is usually present in very small quantities and can remain undetected without proper testing.
All lubricants and oils can hold a small amount of water naturally, depending on their type, temperature, and chemical composition.
Dissolved water forms when moisture from the air comes into contact with the oil and becomes absorbed.
Common causes include:
Exposure of lubricants to open air during handling
At this stage, the oil may appear clear even though water is present at a molecular level.
While small amounts of dissolved water are usually harmless, excess moisture can cause the oil to become saturated.
Once the saturation point is reached, any additional water will start to form emulsions or free water, leading to:
Formation of sludge and oxidation products
High dissolved water levels can also reduce dielectric strength in transformer and turbine oils.
Perform regular oil analysis to measure water content (using Karl Fischer titration or similar methods).
Maintaining low water content helps extend oil life and ensures reliable equipment operation.
