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Non-ferrous metal inhibitor

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New, improved lubricants arrive on the market at regular intervals, and the formulation of these high-tech products, in most cases based on synthetic base oils and additives, also has direct consequences for lubricant analysis. That‘s why OELCHECK continually invests in innovative testing procedures and develops new analysis methods based primarily on test procedures that have become standard. A brand-new development is to inspect the remaining non-ferrous metal inhibitor content in waste oils using high-performance liquid chromatography (HPLC). Previously used by OELCHECK for coolant analysis, the HPLC method can now be applied for early detection of the breakdown of non-ferrous metal inhibitors used in gear oils to prevent non-ferrous metal wear.

Our new analysis method of non-ferrous metal inhibitor (NFMI) content developed from an exciting case that initially had OELCHECK tribologists scratching their heads. Oil from the mean gear of a wind turbine filled with 600 litres of synthetic gear oil was inspected three times over a period of six years. The analysis values obtained showed that no oil change was necessary, as all of them were normal. However, a closer look at a sample of the oil that had been in use the longest revealed changes that were completely outside what was expected. The oil samples were taken at irregular intervals of 12,600, 43,800 and 52,700 operating hours, respectively. They revealed a change in the colour of the oil that was documented photographically in the lab report.

Although there is no standardised evaluation for oil colour, this enables specialists to make an initial appraisal of oil changes in comparison with a fresh or previous sample. In this case, the first sample was still light and clear, but after that the oil had discoloured to a dark brown within the relatively short space of time up to 52,700 operating hours. As the remaining analysis values (with the exception of copper content) showed nothing unusual, the darkened oil alone revealed no clues to suggest that an oil change was needed. Nevertheless, the tribologists at OELCHECK were alarmed. Due in part to the copper content, they first examined the visual change since the last sample more closely under the microscope and compared it with the previous samples and with fresh oil.
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How clean are your sample bottles?

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We have the hydraulic fluids from our construction machinery analysed on a regular basis with analysis kit 2 for mobile hydraulics. This also includes a particle count in accordance with ISO 4406. How useful is an analysis of this kind if the hydraulic fluid is sent to the lab in a sample bottle that contains particles itself? Are the results of the analysis influenced by the transportation of the sample in the sample bottle? How clean are your bottles? Are you able to provide a statement on how many particles are present in a new sample bottle and how large they are?
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AN (Acid Number) standard change

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With very few exceptions, mineral oil-based or synthetic base oils are neutral, i.e. they have a pH value which is around 7 on a scale of 0 (extremely acidic) to 14 (extremely alkaline). The pH value is nevertheless influenced by additives that are added to the base oil. Some combinations, such as anti-wear and anti-corrosion additives, have a slightly acidic reaction. The acidic compound content of the oil also continues to increase during practical use, for example as a result of oxidation. The longer an oil is in use, the higher the operating temperatures, while the greater the number of contaminants in the oil, the more the level of acid-forming oil oxidation rises. An accumulation of acids in the oil accelerates oxidation and can increase the oil‘s viscosity. In extreme cases, oil that has become too thick is no longer conveyed in sufficient quantities to the lubrication point. If free acids are present and the corrosion inhibitors are used up, this can lead to the corrosion of all oil-covered surfaces.
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