By Steven Lumley
FULLY formulated lubricants have many functions and are classified into five fundamental groups: reducing friction/wear, dissipating heat from critical machine components, removing/suspending deposits, protecting metal surfaces from degradation/corrosion and acting as a structural material.
Lubricants serve a diverse range of applications – from car engines to water pumps to even the bobbin cases of sewing machines, each requiring different combinations of base oils and additives.
Blending and formulating lubricants is complex, requiring a high degree of engineering and complex chemistry, and in-depth understanding of the ingredients’ chemical qualities and how those chemicals interact.
Base oils themselves perform most of a lubricant’s functions but can only do part of the job. Additives are needed when a lubricant’s base oil doesn’t provide all the necessary properties. They improve the good properties of the base oils and minimise the bad.
Typical lubricants contain a base oil, an additive package and, optionally, a viscosity index (VI) improver. Lubricant additives are organic or inorganic compounds dissolved/suspended in oil.
Not all lubricants contain the same combination of additives and certainly not in the same treat rates. Additive concentrations range between 0.1% to 30% of oil volume, depending on the application. Turbine, hydraulic and industrial gear lubricants demand much lower treat rates of additive packages compared to automotive gear, transmissions, petrol and diesel engines, which are the most demanding, requiring the most additives.
Different lubricant additives have different functions. They are also chosen for their ability to mix easily with the selected base oils, to be compatible with other additives and to be cost effective.
The geometry and metallurgy of the components, operating temperatures, load, potential exposure to contaminants, combustion products and typical drain intervals – these are all considered when selecting the ideal cocktail of additives.
The optimal base oil / additive combination allows the finished lubricant to meet specified properties and performance characteristics outlined by OEMs and lubricant standards organisations.
A final note about lubricant additives is that, like most things in life, they do not last forever. All additives are sacrificial in nature and are gradually used up over time and this process leads to oil degradation which can have an adverse effect on the mechanical system been lubricated.
For this reason, monitoring the physical and chemical properties of your lubricant with oil analysis is a cornerstone of any condition monitoring programme.
Steven Lara-Lee Lumley is Technical Manager at WearCheck