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Oil Analysis And Testing

Karl Fischer

Karl Fischer Moisture Titration – for determining water content.

Oil samples are analyzed for water content using the Karl Fischer moisture titration. This analysis procedure is particularly useful at detecting both high moisture contents and trace moisture contents. The process was invented by a German chemist named Karl Fischer in 1935.

The testing process involves a chemical reaction between water and Iodine within a reagent. Iodine is dispensed into the sample in small amounts until the reaction endpoint is reached. The amount of Iodine used in the reaction is directly proportional to the amount of water within the sample. The following reaction takes place (in the presence of a solvent mixture):

I2 + 2H2O + SO2 → 2HI + H2SO4

Karl Fischer titration’s are extremely accurate and can give results ranging from 1ppm to 100%. Another significant advantage is that unlike the conventional Loss On Drying method (LOD), this process is not adversely affected by the presence of other volatiles – the LOD method detects the loss of any volatile substance, not just water.


The Volumetric Karl Fischer at OCLS

The Volumetric Karl Fischer at OCLS


The effects of water contamination can be disastrous and can ultimately lead to catastrophic failure of a machine.

We can then see how the oil condition has changed from its virgin state to its used state and make recommendations as necessary.

OCLS Uses both volumetric and coulometric methods for moisture determination by Karl Fischer. This allows determinations of a very wide range of moistures levels to be determined, such as in transformer oils.

  • Rust: When water comes into contact with iron or steel surfaces, a chemical reaction takes place producing a red/brown oxide (rust). Rust particles are very abrasive and can go on to expose fresh metal surfaces which can also rust. This rate can increase if left unchecked.


  • Corrosion: Water can pair up with gasses and acidic compounds present within the oil and can go on to corrode metal surfaces. Erosion If free water comes into contact with hot metal surfaces, it can undergo instant flash evaporation which can cause pitting in the area it came into contact with.


  • Cavitation: When any water vapour (steam) bubbles are exposed to extreme pressures, e.g. in a pump or high-load zone, the water vapour bubble implodes and simultaneously converts back to its liquid water. This water droplet can impact any metal surface in the form of a high-pressure, needle-like jet which can cause surface fatigue.


  • Microbe Growth: Free water contamination in diesel fuel will separate out into two insoluble layers. Microbes can begin to grow at the fuel-water interface, the point where the two insoluble liquids meet (see Fuel Filtration.) This area provides optimum living conditions for bacteria. Microbes can block fuel filters which can lead to further problems.