Basics of Friction, Wear & Lubricants & Tribology, Tribosystem & Lubrication. In both articles, we have shared What friction & benefits is & dis-benefits of friction & also we have shared how you can reduce the harmful effects of friction by using lubrication.
We already know about the Lubricating Oils. Now we are discussing about the lubricating greases.
Lubricating greases are used to lubricate mechanical systems & tools that cannot be automatically supplied with oil. Greases are applied to mechanisms that can be lubricated infrequently and where a lubricating oil would not stay in position. They also act as sealants to prevent water ingress.
Lubricating Oil = Base Oil + Additive + Solid Lubricants.
Lubricating Grease = Base Oil + Additive + Solid Lubricants + THICKENER
What is the difference between oil and grease?
Oil and grease are two very familiar terms, but most people aren’t clear on precisely the difference is… unless they happen to work in lubrication, that is! There are some situations where oil is the better choice and some when grease works better. We will also discuss why in some situations or some applications, grease is a better choice & why in some situations or some applications, oil is a better choice for lubrication purposes. So, what is the difference between oil and grease? Very simply:
- Greases are usually oils with thickener added.
- At room temperature, greases are usually solid, while oils are usually liquid.
- All oils can be turned into greases, but not all greases come from oils.
- Greases are typically only used on machinery, tools, or equipment, while oils have many other non-industrial uses.
- Greases ( mostly) are of Thixotropic Structure (Thixotropy is a time-dependent shear thinning property. Certain gels or thick or viscous fluids under static conditions will flow (become thinner, less viscous) over time when shaken, agitated, shear-stressed, or otherwise stressed (time-dependent viscosity); oils are not. All oils and fluids are Newtonian Fluids (A Newtonian fluid’s viscosity remains constant, no matter the amount of shear applied for a constant temperature.. These fluids have a linear relationship between viscosity and shear stress), but greases are generally non-Newtonian Fluids.
So, now we have understood that the main difference between Lubricating Oils & Lubricating Grease is THICKENER. In Lubricating Oil, there is no thickener added, but Greases are usually oils with thickener added.
What is THICKENER
A thickener is a thickening agent is a substance that can increase the consistency of a liquid without substantially changing its other properties. Thickeners are used in the lubricating industry. Edible thickeners are commonly used to thicken sauces, soups, and puddings without altering their taste; thickeners are also used in paints inks, explosives, and cosmetics.
Tasks of Thickener
- Thickens the Oil.
- Control the release.
- Seals the friction point.
- Protects against moisture & Dust.
Types of Thickeners
- Non Soaps
Soap thickened greases consist of simple, mixed and complex soaps.
These include organic & inorganic substances. The main non soap thickeners used in the manufacturing of lubricating greases are
- Plastics (PTFE).
Table of Different Types of Grease Thickeners & their characteristics
When discussing different thickeners, which converts a lubricating oil into greases, we must understand the grease compatibility because the decision to make a lubricant change within a machine should always be carefully evaluated. It is essential to be cautious when switching from one lubricant type to another lubricant type. Due to grease’s fundamental properties, it can be challenging to remove all of the old greases before introducing new grease to the application; because of this challenge, the decision to use a new grease in an application must be managed with grease compatibility in mind.
B = Borderline C = Compatible I = Incompatible
Note: This chart is a general guide to grease compatibility. Specific properties of greases can dictate suitability for use. Testing should be conducted to determine if greases are compatible.
Compatibility of grease mixtures is typically categorized as given below
- Compatible – The properties of the mixture are similar to those of the individual grease.
- Incompatible – The properties of the mixture are significantly different than those of the individual greases.
- Borderline – The properties of the mixture may or may not be acceptable, depending on the nature of the application.
Greases are considered to be compatible if the below mentioned conditions are met
- The dropping point of the mixture is not significantly lower than that of the individual greases.
- The mechanical stability of the mixture is within the range of consistency of the individual greases.
- The change in consistency of the mixture in elevated temperature is within the range of the change in consistency of the individual greases.
Conducting and non conducting lubricating oils
Here we have tried shared the basic about difference Lubricating Oils & Lubricating Greases in simplest way. In our next article we will share different types of Additives used in any lubricating oil or greases, the role of Additives & why Additives are soo important.
NOW, what type of greases are you using in which type of applications & why? Let me know me in comments.
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You can also read below articles for more information.
- Industrial Lubricants Manufacturing Companies
- Reliable Lubrication Solution for Caster Application in Steel Making Plants
- Reliable Lubrication Solution for Rolling Mills (Metal Working) in Steel Plants