| OELCHECK test instrument: | Coulometry: Metrohm 851 Titrando with 874 Oven Sample Processor Volumetry: Mettler Toledo V20 – Volumetric KF Titrator |
| Sample quantity: | 3 ml |
| Unit: | Coulometry: ppm or mg/kg Volumetry: % |
| Test result: | Water K.F. |
| Result range: | Coulometry: 30 - 50.000 ppm Coulometry transformer oils*: 2 – 50,000 ppm Volumetry: 0.1 – 100 % |
| Analysis for: | Coulometry: synthetic oils, bio-oils, transformer oils*, greases, refrigerator and compressor oils, fuels Volumetry: lubricants with high water content, HFC fluids, coolants |
| Brief description: | In the indirect coulometric Karl Fischer method, the water is evaporated from the sealed sample by heating it to over 100 °C. Via a hollow needle, it is transported with nitrogen into a titration vessel. There, the water reacts electrochemically with the K.F. solution. The water content can be determined precisely from the inflection point of the titration curve. In the direct volumetric Karl Fischer method, the sample is titrated with Karl Fischer reagent to the endpoint. An electrode detects the endpoint, and the consumption of reagent up to the endpoint serves as a direct measure of the water content of the sample. |
| Statement: | Depending on the oil type and application, the water content in a lubricant must not exceed certain permissible values. Excessive water can cause, for example, corrosion, cavitation, or oil oxidation. In coolants, the water content additionally indicates the dilution of the concentrate. |
| Underlying test standard: | DIN 51639-5, ASTM D6304, ASTM D1123 |
| Deviating methods: | DIN 51777, DIN EN ISO 12937-B: direct coulometric procedure |
