Quality and Performance of Reclaimed Mineral Oils

The results show that reclaiming aged transformer oils can restore their properties to a level comparable with re-refined alternatives and compliant with IEC 60296 requirements for unused high-grade transformer oils, with the exception of color and oxidation stability. The reclaiming process effectively removed acids, polar contaminants, potentially corrosive sulfur, and stray-gassing tendencies. Two of the three reclaimed oils met the acceptance limits for acid formation and sludge after 500 hours of accelerated ageing during the oxidation stability test, although all exceeded the limit for dissipation factor. The tests indicate that the reclaimed oils may exhibit different aging behaviors than the re-refined oils under accelerated aging conditions, with a more pronounced increase in dissipation factor relative to acid formation during accelerated aging. This behavior is considered to be primarily related to the original manufacturing processes rather than limitations of the reclaiming itself. Furthermore, the accelerated aging tests impose thermo-oxidative stresses well beyond those encountered during normal transformer operation. Across all other evaluated properties, the reclaimed oils showed performance levels essentially indistinguishable from both re-refined oils and unused high-grade transformer oils.