OELCHECK measures refractive indices using the RX40 Refractive Index Cell Module from Mettler Toledo. This produces the wavelengths of light required with high accuracy, and determines refractive indices within a value range of 1.3200 to 1.7000. The refractive index can then be used to determine the mixing ratio of two components.
In the case of coolants, the concentration and quantity of ethylene glycol or propylene glycol mixed into the water are determined. This is important information, because the glycol content affects the thermal characteristics of the coolant. Concentrations of inhibitors, which give the water additional protection against corrosion, can also be determined in this way. As it is difficult to identify exact proportions of ethylene and propylene glycol using the refractive index alone, OELCHECK also determines the density of the coolant mixture. Comparison of these values then makes it possible to make a clear assessment.
In the case of base oils of varying origins and compositions, refractive indices enable us to get to the bottom of what mixtures contain. In order to do this, we generally measure not only refractive index, but also density, viscosity index, and IR spectrum. The values for hydrocarbons (mineral or synthetic), esters, and glycols vary less than they do in the case of water-glycol mixtures. For silicone or perfluorinated polyether (PFPR) based oils, on the other hand, there are clearly distinctive values. Particularly with mixtures involving silicones and PFPEs, which are not compatible with other lubricants, the consequences can be very severe. Silicone oils, such as those used in some non-water miscible metalworking fluids or as insulating oils in transformers, must remain entirely free from other types of oil. PFPE-based lubricants, which have an exceptional performance capacity at high temperatures and are resistant to chemicals, must likewise not be contaminated with other lubricants. Determining their refractive indices in the laboratory allows mixtures that are hazardous with regard to these products to be easily identified.