Condition monitoring specialist company, WearCheck has launched a lube kitchen series, created by Steven Lumley, technical manager at the company. In it, she explores the world of lubricant additives, detailing their function, how they work and their application. Part 1 focuses on the classification of lubricants.
A fully formulated lubricant can have many functions but they generally fall into five fundamental groups. Lubricants are used to reduce friction and wear, dissipate heat from critical machine components, remove and suspend deposits that may affect performance, protect metal surfaces from degradation and corrosion as well as act as a structural material.
Lubricants serve a diverse range of applications, everything from your car’s engine to the water pumps at a nuclear power station to even the bobbin case of a small sewing machine, with each requiring a different combination of base oils and additives.
The blending of a lubricant is a complex process that requires a high degree of engineering and some pretty complex chemistry in the lube kitchen, as formulating lubricants requires an in-depth understanding of the chemical qualities of everything that goes into the mix and how those chemicals interact − quite a balancing act, when you think about it!
Base oils themselves perform most of the functions of lubricants, but they can only do part of the job. Additives are needed when a lubricant’s base oil doesn’t provide all the properties the application requires. They are used to improve the good properties of the base oils and minimise the bad. Typical lubricants are composed of a base oil, an additive package and, optionally, a viscosity index (VI) improver. Lubricant additives are organic or inorganic compounds dissolved or suspended in oil.
Not all lubricants contain the same combination of additives and certainly not in the same treat rates. Additive concentrations can range between 0,1% to 30% of the oil volume, depending on the application. For example, turbine, hydraulic and industrial gear lubricants demand much lower treat rates of additive packages compared to automotive gears, transmissions and petrol and diesel engines, which are the most demanding and require the most additives.
There are many lubricant additives available and they are selected for use based upon their ability to perform their intended function. They are also chosen for their ability to mix easily with the selected base oils, to be compatible with other additives in the formulation and to be cost effective.
Added to this, the geometry and metallurgy of the components, the operating temperatures, load, potential exposure to contaminants, combustion products and typical drain intervals are also taken into consideration when selecting the ideal cocktail of additives for a specific application.
Ultimately, the optimal combination of base oils and additives allows the finished lubricant to meet specified properties and performance characteristics outlined by OEMs and lubricant standards organisations.
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