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Karl-Fischer

  
OELCHECK test instrument: Metrohm 774 oven sampler with coulometer 756 KF
Mettler Toledo V20 - Volumetric KF Titrator
Sample quantity: 3 ml
Unit: ppm or rather mg/kg
Test result: water K.F.
Result range: coulometric: 10 - 50,000 ppm
volumetric: 1000 - 1 Mio. ppm
Analysis for: coulometric: synthetic oils, bio-oils, transformer oils, greases, refrigerator and compressor oils, fuels
volumetric: lubricants with high water content, HFC fluids, coolants
Brief description: In the indirect coulometric Karl Fischer method, the water from the sealed sample is steamed away by heating it to temperatures over 100 °C. It is channelled into a titration vessel using a hollow needle and nitrogen. Here, an electrochemical reaction takes place between the water and the KF solution. Once the transition point of the titration curve has been reached, the exact water content can be stated.
Statement: The water content in a lubricant should not exceed certain permissible values, depending on oil type and use. Too much water in the oil can cause problems such as corrosion, cavitation or oil oxidation.
Underlying test standard: DIN 51777-1, DIN 51777-2, ASTM D6304
Deviating methods: DIN EN ISO 12937-B: direct coulometric method