Selected metallic elements are present in used oil as dissolved solids and microscopic particles. Spectrochemical Analysis identifies and measures these elements in parts per million by weight. They are then grouped into three main categories for analysis.
Relative motion between lubricated parts is always accompanied by friction between the opposing part surfaces. Despite the fact that these surfaces are usually coated with an oil film, friction wears them away. As parts wear, some of the particles produced are small enough to remain suspended in the circulating oil. Since these wear products are composed of the same materials as the surfaces from which they originated, the level of each wear metal remaining in the used oil indicates the relative wear rate of the lubricated parts.
Depending upon the circumstances, many different substances may be classified as contaminants. Silicon, in the form of silicon dioxide (sand), is one of the most common contaminants monitored with
Spectrochemical Analysis. Similarly, increases in aluminum or barium can indicate grease contamination in an oil system if the grease contains metallic soaps. Although the term contamination is commonly associated with substances entering a component’s oil system from an outside source, wear metals themselves are also a form of contaminant.
Additives are chemical compounds added to oils, fuels and coolants to impart specific beneficial properties to the finished product, such as anti-wear, anti-oxidant, detergency and discrepancy. Additives create new fluid properties, enhance properties already present and reduce the rate at which undesirable fluid changes take place during service.