Karl Fischer Moisture (KF)
Standard Test Method for Water in Insulating Liquids by Coulometric Karl Fischer Titration. ASTM D1533
Water content is a chemical property of new oil related to its purity. New oil leaves the refining process with very low water content, but can pick up additional moisture during storage, transfer to delivery containers or vehicles, transportation, and installation. A typical specification value for new oil, as received from the supplier, is a maximum of 25 ppm moisture. When new oil is installed in new equipment, it is typically processed through filters, heat, and vacuum. A typical specification value for new oil leaving the processor to be filled into new equipment is a maximum of 10 ppm moisture.
Once the oil has been installed in the equipment, the moisture content of the oil in ppm no longer tells the complete story. More important values from an operational and maintenance standpoint are the percent saturation of the oil and the percent moisture by dry weight of the solid insulation. These are calculated using the moisture content of the oil in ppm and the temperature of the oil at time of sampling. A typical specification for % moisture by dry weight for a new unit, prior to energizing is 0.5%.
As an in-service oil test, moisture content is a critical parameter. Again, the critical values are the % saturation and the % moisture by dry weight calculated from the oil temperature and the moisture content in ppm reported by the Karl Fischer Titration.
For fluids other than mineral oil dielectric fluid and for oil-filled equipment other than transformers, % saturation and % moisture by dry weight are not calculated. Evaluation of moisture results using ppm values and our established criteria provide a superior basis for management decisions in these cases.
Water content is a chemical property of new oil related to its purity. New oil leaves the refining process with very low water content, but can pick up additional moisture during storage, transfer to delivery containers or vehicles, transportation, and installation. A typical specification value for new oil, as received from the supplier, is a maximum of 25 ppm moisture. When new oil is installed in new equipment, it is typically processed through filters, heat, and vacuum. A typical specification value for new oil leaving the processor to be filled into new equipment is a maximum of 10 ppm moisture.
Once the oil has been installed in the equipment, the moisture content of the oil in ppm no longer tells the complete story. More important values from an operational and maintenance standpoint are the percent saturation of the oil and the percent moisture by dry weight of the solid insulation. These are calculated using the moisture content of the oil in ppm and the temperature of the oil at time of sampling. A typical specification for % moisture by dry weight for a new unit, prior to energizing is 0.5%.
As an in-service oil test, moisture content is a critical parameter. Again, the critical values are the % saturation and the % moisture by dry weight calculated from the oil temperature and the moisture content in ppm reported by the Karl Fischer Titration.
For fluids other than mineral oil dielectric fluid and for oil-filled equipment other than transformers, % saturation and % moisture by dry weight are not calculated. Evaluation of moisture results using ppm values and our established criteria provide a superior basis for management decisions in these cases.