Just about any piece of mechanical equipment requires the use of a lubricant. From small machines to complex engines, having proper lubrication is critical to making sure your equipment runs longer and more efficiently.
But why exactly do we need lubrication? Quite simply, lubricants, whether they are oils or greases, reduce friction between surfaces. This reduces heat generation and prevents metal surfaces from grinding against each other.
Even metal surfaces that may seem smooth have peaks and valleys (called asperities) that cause friction and damage. Lubricants create a barrier between these surfaces, which prevents wear and breakage while reducing heat.
Lubricants have a wide range of properties that impact their physical and chemical properties. Knowing about these properties is important in determining which lubricant is best for which situation.While there are many properties, the most important are:
While there are other properties to consider when choosing a lubricant, these are often considered the most important.
The two main types of lubricants are oils and greases. Both aim to lubricate equipment and prevent damage through metal to metal contact. However, there are a few key differences in how they are used.
To put it simply, grease is oil mixed with a thickener and other additives. These thickeners impact grease capability and compatibility. They also impact grease consistency, which is measured in NLGI (National Lubricating Grease Institute) Grades. The NLGI grade is a measure of a grease consistency. The higher the grade, the thicker the grease.
But why use grease over oil? Greases are better for leakage control and provide better seals against contaminants. Grease can remain in equipment longer and tolerate a variety of conditions. It is also easier to apply in most industrial settings. The best greases should tolerate some contamination, resist leakage and change in consistency and be compatible with all seals.
Of course, oil has advantages as well. It’s easier to drain, easier to control the amount you are using and much cleaner than grease. It also provides better cooling properties. Oil is also better for extending the life of bearings, as oiled bearings can last twice as long as greased ones.
Oil can be broken down into three different categories, conventional (or mineral), synthetic and synthetic blends.
Conventional/Mineral: Oils created by extracting materials. These oils are a mix of different size molecules.
Synthetic: Man made oil created by adding materials. The molecules of these oils are uniform in size and shape.
Blends: Blends of both synthetic and conventional oils.While Synthetic and conventional oils might appear the same to the naked eye, they are different at the molecular level.In general, synthetics provide low pour points, high viscosity index and better lubricity than conventional lubricants. They tend to perform better at high temperatures, last longer and generate less waste. HOWEVER, this does not mean synthetics are the correct choice for all applications. Most synthetics are NOT compatible with other oils, be they synthetic, conventional or blends. Mixing synthetics with these can cause serious engine damage. Synthetics are also a poor choice for wet conditions, as they will absorb large amounts of water quickly and create acid. Finally, synthetics have such powerful cleaning properties that they can remove paint or even dissolve seals. Grease thickeners can be divided into two categories, soap and non-soap. More than 90 % of thickeners are soap based. These thickeners can be broken into three groups:
Simple – A simple soap resulting from the reaction of a single acid, usually 12 HSA and a metallic hydroxide, usually lithium, aluminum, calcium or sodium. The metal used defines the type of soap, with lithium being the most common.
Mixed – Produced by a reaction of acid with two metallic hydroxides. Not common.
Complex – Reaction of an acid with a short chain complexing acid, like azelaic acid. Usually has much better high temperature properties.
Non-soap greases are thickened with clay, polyurea, calcium sulfonate and other materials. These greases provide strong heat and water resistance without sacrificing other properties. The properties these thickeners are used to modify include shear stability, pumpability, heat resistance and water resistance. Thickeners impact greases as follows.
Calcium – Provides good water resistance and shear stability at the cost of pumpability and heat resistance
Sodium – Provides good heat resistance while sacrificing utility in the other properties
Barium – Good heat and water resistance, but poor pumpability
Lithium 12 OH Stearate – Makes improvements to all areas, particularly to shear stability and water resistance
Lithium complex – Provides a boost to all properties
Calcium Complex – Provides strong water resistance, but not very pumpable
Aluminum complex – Good heat and water resistance.
Clay, Polyurea and Calcium Sulfonate – Good water and heat resistance.
Food grade lubricants are special products used in applications where contact with food or beverage related items could potentially take place. These products must perform all the duties of a regular lubricant while also meeting certain guidelines for food safety. There are three different classifications of food grade lubricants:
H1 Lubricants – Used in applications where contact with food could take place, such as food processing equipment. In general, the amount used should be the minimum possible to get the desired effect of the lubricant.
H2 Lubricants – Used in food industry applications where there is no possibility of making contact with food. These lubricants are used on machine parts and closed system that will never touch any edible product
H3 Soluble Oils – Applied to equipment that will directly contact food, usually for the purpose of cleaning and preventing rust.
Since 1999, NSF International manages the registration and certification process for food grade lubricants. Food grade lubricants are blended with white oil base stocks and one of a limited number of approved thickeners.
