How to Determine Water in Oil

Noria Corporation

"The laboratory that our plant uses for oil analysis just sent us a report suggesting that there is water in our oil. How does a lab determine water in oil?"

The issue of water contamination in oil can be devastating. After particle contamination, water is considered the second most damaging form of contamination for a lube system. Water in oil can cause issues such as higher viscosity, reduced load-carrying ability and additive depletion. Some of the effects it may have on your machinery include corrosion on metal surfaces, filter plugging and cavitation.

Water can exist in three states: dissolved, emulsified and free. Dissolved water is similar to humidity and cannot be seen in oil. Emulsified water is when the amount of dissolved water is greater than the saturation point. Free water is when the water content in oil visibly separates.

So how does a laboratory determine that you have water in your oil? There are primarily two types of tests being used in laboratories today: Fourier transform infrared (FTIR) spectroscopy and the Karl Fischer titration test. Of these two methods, FTIR is generally less expensive but also not as accurate. FTIR uses an infrared light, which is passed through an oil sample. The light absorption at different wavelengths in the spectra is then measured to indicate the concentration of water. This test is restricted to lower detection limits of approximately 1,000 parts per million (ppm).

The Karl Fischer titration test is much more accurate and has the ability to measure as little as 1 ppm of water in oil when used correctly. This method uses two types of titration to identify trace amounts of water in a given sample: coulometric or volumetric. The principles are the same for each, except volumetric uses a titrant solution. This testing method can be very beneficial because it allows you to analyze solids, liquids or gases. The disadvantages of the Karl Fischer titration test include its cost and the amount of time required when water concentrations are high.

Routine oil analysis should be performed along with water content testing to ensure acceptable levels are maintained. Proper monitoring helps negate any machine failures or unscheduled downtime that may occur due to water contamination. Either onsite testing at your facility or sending samples off to a lab can serve as an effective way to measure the water content in your oil.

Subscribe to Machinery Lubrication