Lubrication refers the application of a dedicated film that reduces friction and wear between moving surfaces that are in contact with each other. Common lubricants include natural and synthetic oils and greases, which can take the form of solids, fluids or even plastic substances. While this may be a valid description, it doesn’t encompass all the roles that lubrication fulfils.
As mentioned, grease and oil are among the various substances used for surface lubrication. Oils can be natural, using a mineral or vegetable base, or chemically manufactured. They can also be created with a combination of natural and man-made ingredients, sometimes called semi-synthetics. Greases, on the other hand, have a different consistency. Although they are made from oil, greases also include a thickener, giving them a more solid appearance. However, it is still the oil the grease contains that performs the task of lubrication.
Formulating a lubricant
What a lubricant will be used for will ultimately determine what oil should be used as the base. For example, environmental concerns may require a foundation oil to be vegetable-based, while lubricants that need to work effectively under extreme conditions may benefit from a synthetic base.
Working alongside the base oil, lubricants also feature cleverly formulated additives that either cancel out or add to properties that are already present in the base oil. The number and type of additives in any given lubricant will depend on the kind of lubrication and its intended application.
In some cases, a dispersant additive may be included. Dispersants ensure insoluble material stays together, so that it can be more effectively removed by filters. In environments that see extreme changes in temperature, an additive that improves the viscosity index may be part of the additive package. Such additives feature long molecules that will stay conglomerated in colder conditions and can then unfurl when subjected to hotter temperatures. This process impacts the oil viscosity, allowing it to flow more freely in lower temperatures, while retaining the qualities it boasts under hotter conditions.
The primary functions of lubrication
The main roles of lubrication are to reduce friction, protect against wear and prevent corrosion to equipment occurring. Lubricants must also control temperature by dissipating heat and mitigate contamination by collecting and carrying any debris to a sump or filter. In hydraulic equipment, they work to transfer power, and the final role of lubrication is to create a fluid-film seal.
While the functions of wear prevention and friction reduction are sometimes employed interchangeably, there is a difference. Wear is, in actuality, the material loss due to fatigue, friction and corrosion, while friction refers to the force that is resisting motion.
The reduction of friction is the prime objective of any lubricant, however, there are multiple other benefits to the process of lubrication. Lubricant films can act as a defence against corrosion when safeguarding surfaces from water and other corrosives. They also prove invaluable in removing contamination from mechanical systems and absorbing unwanted heat, cooling parts and allowing them to operate at optimum without damage.