What are the essential properties of the lubricating oils available in the market?
A lubricant is a substance, usually organic, introduced to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, transporting foreign particles, or heating or cooling the surfaces. The property of reducing friction is known as lubricity.
In addition to industrial applications, lubricants are used for many other purposes. Other uses include cooking (oils and fats in use in frying pans, in baking to prevent food sticking), bioapplications on humans (e.g. lubricants for artificial joints), ultrasound examination, medical examination. It is mainly used to reduce friction and to contribute to a better and efficient functioning of a mechanism.
Why do we need to lubricate? In this first part of a two-part introductory primer on industrial lubricants, we take a closer look at the need for lubrication and the key properties of lubricating oils. Regardless if you’re a seasoned pro or a new aspiring talent in this industry, this article will help you understand their significance when choosing the right lubes with the right characteristics for various industrial activities.
Oft-regarded as the lifeblood of machinery, lubricants are an essential component across multiple industrial activities. From bearings to engines to hydraulics, they are used to keep industries running smoothly by:
Lessening wear and tear
Reducing friction
Removing heat
Preventing rust and corrosion
Removing contaminants
Regardless if you’re a seasoned pro in the industry or a new aspiring talent, below is a guide on the basics of mineral and synthetics lubricating oils, beginning with its properties, to help you gain a firmer grasp of this essential industrial component.
- Viscosity
Viscosity is defined as the fluid’s internal resistance to flow. The higher the viscosity of the fluid, the slower it flows. If you want your film to stay put at lower speeds, you need higher viscosity.
Considered the most important property of a lubricant, viscosity serves to form a lubricating film, cool machine components, and seal and control oil consumption. It has to be balanced for load, temperature and speed. Below is a table to illustrate how each factor affects how high or low a viscosity should be.
Note: The numbers in the parenthesis are unitless numbers that show the difference between viscosity at 40 degrees Celsius and 100 degrees Celsius.
In the graph above, notice that the slope of each line is different over the same temperature range, depending on its viscosity: the lowest VI has the highest slope; the highest VI has the least slope.
- Thermal Stability
Thermal stability refers to the ability of lubricants to resist breakdown at high temperatures. Poor thermal stability can result in sludge, deposits and increased viscosity.
- Oxidation Stability
Oxidation stability refers to the ability of a lubricant to resist the chemical combination with oxygen. It can result in the creation of sludge deposits and increased viscosity.
Oxidation stability is accelerated by heat, light, metal catalysts, acids formed by water contamination and other contaminants.
Pour Point
Pour point is the lowest temperature at which an oil will flow under prescribed test conditions. It is affected by the amount of wax particles removed during the processing of crude.
The more wax particles there are, the higher the pour point. The fewer wax particles there are, the lower the pour point.
Demulsibility
Demulsibility is another important property of lubricating oils. It is the ability of an oil to separate from water.
- Flash Point
Flash point is determined by heating the oil until vapours form; a flame is then passed across the oil. The flash point is the temperature at which the oil sparks, but a flame is not sustained.
The flash point for lubricating oils is typically 204°C (400°F) or above.
ire Point
Fire point is determined in a manner similar to flash point. Oil is heated until vapours form; a flame is then passed over the oil. The fire point is the temperature at which the oil sparks and the flame is sustained.
The fire point for lubricating oils is typically 371°C (700°F) or above.
Next week, we will take a look at what are the various elements that need to be lubricated.
lubricating oil filtration machine
lubricating oil filtration machine