On a daily basis, humans have been observed to use machines all the time, everywhere, and for almost everything. It is almost as if we depend on them, rely on them, and have an unprecedented urge to always have one on hand. Another evident observation of how frequently we use machines is the masses of motorized vehicles that zip through roads and highways. Simply put, machines have integrated themselves into our daily lives and now play a prominent role in our society.
Now, this brings us to ‘’grease’’ and their undeniable importance in the proper functioning of every machine and since we have almost completely substituted all previous forms of communication, transportation, and other aspects of our society with the creation of newer, more industrial methods and apparatuses, it is a necessity to know what grease is, why grease is used, what makes a satisfactory grease, the basic composition of grease and the importance of greasing your machine, etc.
TABLE OF CONTENTS
- What is grease?
- What are the characteristics of grease?
- Types of Grease
- Factors to consider when choosing the right grease for your needs.
- What is the basic composition of grease
- Frequently Asked Questions on Grease
WHAT IS GREASE?
Grease is a solid or semisolid lubricant formed as a dispersion of thickening agents in a liquid lubricant. Grease generally consists of a soap emulsified with mineral or vegetable oil. The lubricating fluid is usually the majority component in the grease formulation. The additives are typically present in relatively low concentrations and are added to the grease to provide enhancement in one of the multiple performance areas. The thickener is what sets grease apart from liquid lubricants. This component gives the grease the property of consistency, making the product semi-solid rather than liquid. Many different chemical compounds can be used to thicken grease.
WHAT ARE THE CHARACTERISTICS OF A GREASE?
Since grease is important in the functioning of our machines there are several properties it possesses that distinguish it from other chemicals.
A common feature of a grease is that they possess a high initial viscosity, which upon the application of shear, drops to give the effect of an oil-lubricated bearing of approximately the same viscosity as the base oil used in the grease. This change in viscosity is called shear thinning.
Grease is sometimes used to describe lubricating materials that are simply soft solids or high viscosity liquids, but these materials do not exhibit the shear-thinning properties characteristic of classical grease. For example, petroleum jellies such as Vaseline are not generally classified as greases.
Greases are applied to mechanisms that can be lubricated only infrequently and where a lubricating oil would not stay in position. They also act as sealants to prevent the ingress of water and incompressible materials. Grease-lubricated bearings have greater frictional characteristics because of their high viscosity.
TYPES OF GREASE AND WHERE TO USE THEM
Calcium grease is one of the first greases that was manufactured for general use. Some of the key features of this multipurpose grease are great water resistance, good corrosion protection, and great mechanical stability. However, this lubricant is best used at lower temperatures, as high temperatures may cause changes in its structure. Today, calcium grease and calcium complex grease are mainly used in marine, industrial, automotive, and agricultural applications.
Lithium grease is a multipurpose grease known for its durability, high viscosity, and stability. It is designed to provide long-lasting protection against oxidation, corrosion, extreme temperatures, and wear and tear. Lithium and lithium complex greases are also characterized by their excellent lubrication, good water resistance, and the ability to withstand high pressure and shock loads. They are suitable for a variety of applications, including automotive, gardening, industrial, household, and demanding metal-to-metal applications.
ALUMINIUM COMPLEX GREASE
Aluminium complex grease has many advantages – it can withstand extremely high temperatures, has impressive water-resisting properties, prevents rust, corrosion, and oxidation, and has good shear stability. Aluminium complex greases are best used in the food industry but are also known to offer excellent results when used in the automotive, steel milling, construction, and farming industry.
Barium complex grease is a high-performance grease widely known for its mechanical stability, high-temperature resistance, ability to withstand heavy loads and high speeds, excellent water tolerance, great oxidation stability, as well as resistance to various chemicals. Barium complex grease is mostly used in demanding, heavy-load applications, such as industrial, aeronautical, marine, and manufacturing applications.
BENTONE (CLAY) GREASE
Bentone grease is a clay-based lubricant developed with the help of bentonite clay. This grease type is often called non-melt lubricant because it has no known dropping point. Its main properties are temperature change resistance, great wear, and tear protection, exceptional water tolerance, good mechanical or shear stability, and impressive adhesiveness. Bentone grease is ideal for highly demanding applications and it’s typically used in the steel, manufacturing, construction, mining, and ceramic industry.
Polyurea grease has become very popular due to its amazing characteristics, such as outstanding water resistance, great oxidation stability, rust and corrosion prevention, durability, versatility, good mechanical stability, as well as high-temperature performance. Due to these features, polyurea grease is recommended for long-life applications and is used across various industries. It is considered vital for the proper lubrication of steel plants and electric motors.
Sodium grease is formulated by mixing soda soap with additives and base oils. Such mixture provides solid shear stability, high dropping point, excellent rust protection, and good lubrication, but has poor water resistance and oxidation stability. Due to its drawbacks, sodium grease is now mostly used for lubrication of rolling contact bearings. Moreover, it is commonly mixed with other greases in an effort to produce grease of higher quality and value.
Kindly note that all types of grease is available at Epoxy Oilserv Nigeria Limited and the seven types of grease can be referred to as multipurpose (MP) greases, extreme pressure (EP) greases, marine greases, heavy-duty greases, specialty greases, automotive greases, industry greases, and so on, depending on the unique properties of base oils, additives, and thickeners used in the process of manufacture.
FACTORS TO CONSIDER WHEN CHOOSING THE RIGHT GREASE FOR YOUR NEEDS
When it comes to purchasing the right type of grease for your individual application requirements, our expert at Epoxy Oilserv Nigeria Limited suggests it best to take several factors into consideration prior to making a final decision.
Base oil represents the foundation of every lubricant and it’s worth mentioning that its type determines the overall performance of the grease in question. Three main types of base oils are mineral, synthetic, and vegetable oils. Synthetic oils are considered to offer the best results in terms of protection, performance, temperature, and weather resistance, followed by good shear stability.
Additives are used to enhance the features and qualities of each grease and boost its performance. The most common additives are extreme pressure additives, oxidation, rust, and corrosion inhibitors, polymers used to increase adhesiveness, insoluble solids, and additives that provide increased wear and tear protection. Also, certain dyes and pigments are added to each grease.
Thickeners are used to enable all grease components to bond better, which increases the overall efficiency of every grease. Types of thickeners that are commonly used are simple and complex soaps, which are based on lithium, calcium, aluminium, sodium, and barium compounds. In addition, certain non-soap thickeners, such as those based on clay and polyurea, can be used to give the grease its consistency.
Consistency is a property defined by the National Lubricating Grease Institute (NLGI) used to determine the level of softness or hardness of every grease. Every grease is assigned a specific NLGI number that goes from 000 to 6. These NLGI grades are then used to express the level of consistency each grease has. So, for instance, NLGI grade 000 grease is completely fluid, NLGI grade 0 greases is described as very soft, NLGI 1 grease is soft, NLGI 2 grease is considered normal, NLGI 3 grease is firm, while NLGI 6 grease is defined as very hard.
Grease viscosity determines its ability to remain stable and offer effective protection against friction. Higher viscosity provides greater stability when grease is exposed to heavy, slow loads, while lower viscosity is ideal for high-speed applications.
WHAT IS THE BASIC COMPOSITION OF GREASE?
As mentioned, grease is composed of oil, thickeners, and additives. Oil and additives typically compose 80 – 90 % of grease, while thickeners can be up to 20% of the grease composition. Oils used may cover the full range of technologies from mineral, PAO, to specialty synthetics and the additives may be based on antioxidants, anti-wear, extreme pressure agents, rust inhibitors, corrosion inhibitors, friction modifiers, dyes, and tackifiers.
FREQUENTLY ASKED QUESTIONS
1. Why is Grease Applied in Machines?
2.How much grease should you put in a bearing?
The application of grease in machines enhances Working efficiency, the Life of the product, gets it away from corrosion and rust, Less energy or fuel consumption, the components will work smoothly and there will be a decrease in noise.
Typical relubrication amounts are 1/3 to 1/2 of the original fill quantity. The proper fill quantity of a grease-lubricated bearing is often specified as a percentage of the bearing’s free space.
3. How do I calculate how much grease I need?
To calculate grease quantity, you need the bearing’s physical dimensions (primarily the outside diameter and width). Once you have these two measurements (in inches), you multiply them together and then multiply by 0.114. The resulting answer is the grease quantity in ounces.
3. Is there a problem with using a combination of two types of oils/greases in the same component where they may come in contact with each other? I want to replace the grease in an existing system with different grease. I can’t clean out all the old grease. Will there be a compatibility issue between the new and old grease?
No, there won’t be compatibility, because when two incompatible greases are mixed, one of two things generally happens: the mixture hardens and will not release any of the oil or the mixture softens and releases all of the oil. In either case, the end result is basically the same; there is effectively no lubrication.
Secondly, in its mildest form, mixing different lubricants may lead to a degradation of lubricant performance. Mixing the same API grades of synthetic passenger car motor oil and mineral oil-based engine oil won’t damage the engine, but you will lose the performance features you expect from the synthetic.
4. Is it OK to leave unused grease in a grease gun?
It is acceptable to leave unused grease in a grease gun. It is recommended to release the pressure from the grease by drawing the handle back and locking the spring in the retracted/compressed position. Otherwise, the oil may separate from the grease over time in storage due to the increased pressure applied by the grease gun spring.
5.There is a burnt odor around a grease-lubricated bearing. Is that a concern?
A burnt odor may indicate overheating of the bearing. A burnt odor suggests that the grease may have been oxidized or thermally degraded. It is prudent to investigate the source of a burnt odor and to determine its cause. If the source of the odor is a grease-lubricated bearing, the equipment should be shut down and the problematic bearing checked.
6.Where is lubricating grease used?
Lubricating grease is used in any type of machinery with rolling or sliding contacts. This can include bearings, gears, couplings, slides, linkages, chains, pin and bushing points, fifth wheels, hinges, constant velocity joints, adjustment mechanisms, etc. Greases are used in components used in electric motors, machine tools, railroad and construction equipment, instruments, household appliances, etc. Greases are also commonly used in slow-speed sliding applications and small gearboxes. A large majority (as much as 90%) of all bearings are grease lubricated.
7. I have opened a new container of lubricating grease and used part of the product. How do I store the remaining product for future use?
The remaining unused lubricating grease can be stored for future use. The surface of the grease should be left smooth (without depressions) by smoothing it with a clean implement such as a spatula or putty knife. The container should then be gently banged on a hard surface to remove any entrained air bubbles and re-smoothed. This is to minimize the separation of oil from the grease during storage. The lid or cover should be placed on the container and secured as well as possible, and the container should be stored indoors out of direct sunlight and away from any heat sources.
8. What lubricating grease should be used in automotive wheel bearings under low ambient temperature conditions?
Most lubricating greases formulated for use in automotive wheel bearings are NLGI 2 grade and are designed to operate at temperatures as low as -40 Â°C (-40 Â°F). The NLGI GC-LB or SAE J310 specifications require the grease to operate at that temperature. For continuous operation at extremely low temperatures (below -40 Â°C/-40 Â°F), a product containing a synthetic base fluid may be considered. In addition, a softer consistency grease (NLGI 1 grade) may be needed.
9. What lubricating grease should be used in automotive wheel bearings that are exposed to a wide range of temperature conditions?
Most lubricating greases for automotive wheel bearings must meet the NLGI GC-LB or SAE J310 requirements. Both of those specifications require that the grease must operate over a temperature range of -40 Â°C (-40 Â°F) to 160 Â°C (320 Â°F). This covers the vast majority of driving conditions.
10.Does the color of lubricating grease have any significance?
The color of unused lubricating grease can be natural (light tan to black, depending on the formulation), or colored with a dye. Black greases typically contain molybdenum disulfide or graphite, both of which impart a dark gray to black color to the grease. The natural color of most greases is light tan to medium brown. Manufacturers add dyes to some greases to give them distinctive colors, either for marketing purposes or to make them easy to distinguish for maintenance personnel.
11. What is the significance of a change in color of lubricating grease during service?
In-service lubricating greases can change color due to thermal degradation, oxidation, or contamination. The dyes used to color greases may lose color intensity when subjected to high temperatures. Highly oxidized greases may become very dark to black. Greases that are contaminated with water sometimes take on an emulsified or milky appearance. When different greases are mixed in service, the resulting color maybe somewhere between the colors of the individual greases.
As stated in this article, grease plays an important part in extending the production and service life of machinery. Particularly of the industrial machines, because they are of high-speed processes, so the components require greasing and maintenance. To increase the life of the equipment and working speed proper greasing and maintenance through industrial greases is necessary and the type of grease you decide to use matters a lot because each lubricant has a different set of characteristics that determine its consistency, viscosity, ability to prevent friction, reduce wear and tear, protect against rust, corrosion, and oxidation, maintain mobility and stop water and other contaminants from coming into contact with the equipment.
It is important to take all mentioned factors into consideration before making a purchase and remember – the right grease for you is the one that meets (and surpasses) all the requirements you have. Contact our expert for more details on the grease that suits your needs.