The RULER does not replace infrared spectroscopy, which provides information on base oil oxidation and aging. It is used by OELCHECK as an additional tool for determining concentrations of active ingredients intended to reduce aging of the base oil. It is particularly helpful in assessing whether a condition-based oil change needs to be performed.
Based on the RULER number, OELCHECK determines the remaining antioxidant capacity in mineral oil-based turbine oils, synthetic hydraulic and gear oils and in lubricating greases as part of trend analyses. From this, OELCHECK draws conclusions about the optimum intervals for changing the oil or the relubrication intervals for grease, among other things.
Changes in base oils and additives also result in adjustments to lubricant analytics.
Turbine oils based on conventional base oils (API group I) predominantly contained phenolic antioxidants in relatively high concentrations, combined with amines, sulfides or phosphates. Modern turbine oils based on base oils of API Group II (hydrotreated), Group III (hydrocracked) or Group IV (PAO) contain mostly aminic antioxidants combined with phenols, the latter, however, only in low concentrations.
While the measurement of aminic antioxidants in modern turbine oils using RULER still works reliably, the reproducibility of the measurement of phenolic antioxidants is significantly impaired due to the very low concentration.
Phenolic antioxidants by infrared spectroscopy
Extensive studies have shown that phenolic antioxidants can be determined more reliably by FT-IR spectroscopy, especially at low concentrations.
The aminic antioxidants can also be detected by FT-IR. However, the "adjacent" wavenumber ranges exhibit interference with other influences. Nevertheless, the repeatability of the quantitative assessment of aminic antioxidants is compromised. In this case, the determination by means of RULER provides significantly more stable results.
Taking this state of affairs into account, OELCHECK has decided to adapt its monitoring concept. In turbine oils, phenolic antioxidants are determined by FT-IR, and aminic AO by RULER. As before, both values are given in % of residual AO compared to fresh oil.
For you, nothing changes in the basic procedure. However, you will receive results that provide more confidence in interpreting the lab results.