DIN 51558-2:2017-07

This document has been prepared by Working Committee NA 062-06-84 AA "Gemeinschaftsausschuss NA 062-06-42 AA/NA 062-06-61 AA" ("Joint working group NA 062-06-42 AA/NA 062-06-61 AA") of Technical Committee Mineralöl- und Brennstoffnormung (FAM) (Standardization Committee for petroleum, fuels, lubricants and related products (FAM)) at DIN Standards Committee Materials Testing (NMP). This document applies to unused and used insulating oils, including those with added non-mineral oil anti-ageing agents (inhibitors). The method is also suitable for testing flame-retardant control fluids. The neutralization number is used to determine the content of acidic components in insulating oils. This method can be used to determine relative changes that occur in insulating oil during operation under oxidizing conditions. Although the titration is carried out under certain equilibrium conditions, it does not measure an absolute acidic property. The values for the acidic components of an insulating oil determined using this method are therefore not comparable with values determined according to DIN ISO 6618 or potentiometric methods.