Lubricating greases are used to keep equipment, machinery, vessels and vehicles and their components protected, clean and moving properly. However, various grease products have been formulated with unique properties to yield different results and serve specific purposes.
Extremely versatile and dependable, grease lubricants have multiple applications and are deployed in a wide spectrum of industries that includes automotive, mining, manufacturing, steel, mining, construction, marine and agriculture, to name but a few.
The type of grease to use is determined by various factors including operating conditions and work rates, compatibility, viscosity, service life and even environmental considerations. If you are baffled by the number of available greases on the market and are struggling to select a product, here we are exploring some common grease lubricants available to purchase. However, first we’ll look at grease and how it differs from oil.
Understanding grease as a lubricant
The role of grease is exceptionally like oils, but the two lubricants aren’t interchangeable. Mostly grease is used in circumstances where using oil is inconvenient or impractical and the question of whether it’s suitable arises when you need a lubricant for a specific application.
Oil is composed of a base oil with additives that are designed to enhance performance, protect, and clean parts. Like oils greases are made using a base oil (typically a mineral oil) and additives but also include a thickening agent to make them more viscous. The common composition of grease includes 80 to 90% base oil, 5 to 10% additives and 10 to 15% thickening agent.
The thickener is a material that, when combined with the base fluid, forms a solid to semi-fluid structure. The main types of thickener used in lubricating grease products are metallic soaps. Types of soap include lithium, aluminium, clay, sodium, polyurea, and calcium among others. The role of the base oil in grease is to perform lubrication. While mineral oils might be more common, synthetic, and bio-based oils are also used. The thickening agent gives greases their characteristic consistency. It’s sometimes described as a sponge that can hold the base oil in position. Additives are typically designed to enhance performance and provide protection to lubricated surfaces and the grease itself.
The largest market share of lubricating greases (75%) involves the use of a lithium-based thickening agent. These products offer excellent mechanical stability and outstanding water resistance, making them ideal for multiple industrial applications. However, lubricant choice for any specific application is always determined by perfectly matching the operating conditions and machinery design with sought-after lubricant properties.
As mentioned, grease an oil aren’t interchangeable. Certain applications will specifically require the use of grease while others will demand an oil. Grease is used with machinery working under extreme operating conditions like high pressure, temperatures, and shock loads, or at slow speeds under heavy loads. Under such circumstances, lubricating grease can supply a far thicker lubrication film. Most oils are far too thin to provide proper lubrication to machinery.
It’s critical to find the optimum heavy-duty grease for an application or operation for many reasons. It can help with worn components by maintaining a thicker film in clearances that have become enlarged by wearing. It can also extend the lifespan of worn components that were oil lubricated previously.
It can also help with parts requiring re-lubrication. Lubricating grease requires less frequent replenishment compared to oil which requires regular top ups in many systems. Grease is also effective at sealing bearings, protecting them against dust, dirt, and other debris.
Consistency is a key aspect of grease. It determines how well it will lubricate without creating too much friction. Greases that are too firm can fail to feed areas of the system needing lubricant, while greases that are too runny can leak out. The consistency of grease always depends on the amount and type of thickening agent used and the base oil’s viscosity.
Maintaining correct lubrication and knowing of which type of grease is suited to your equipment is vital. Machinery that is lubricated properly will work more effectively and last longer.
Grease types and their uses
Below, we detail seven different types of grease and the applications they are best suited to. These grease types can also be called multipurpose (MP) greases, marine greases, extreme pressure (EP) greases, heavy-duty greases, automotive greases, specialty greases and industry greases depending on the specific properties of the base oils, additives, and thickening agents used in their composition.
Lithium Grease
A multipurpose grease, Lithium grease is renowned for its stability, durability and high viscosity. It’s designed to deliver long-lasting protection from corrosion, wear and tear, oxidation, and extreme temperatures. Lithium, as well as lithium complex greases, are characterised by excellent lubrication, water resistance and an ability to cope with shock loads and high pressure. They are a match for many applications that include automotive, industrial, gardening and household, but also demanding metal-on-metal applications.
Calcium grease
Among the first lubricating greases made for general use, calcium grease has a long pedigree. Some of its key features include excellent water resistance, strong corrosion protection, and exceptional mechanical stability. Calcium grease is best employed at lower temperatures however, as higher temperatures can cause changes to its chemical structure. The main applications using calcium greases are marine, automotive, agricultural, and industrial.
Sodium grease
Formulated from mixing base oils and additives with soda soap, sodium grease has much to offer as a lubricant. It supplies good shear stability, a high dropping point, impressive rust protection, and solid lubrication. However, it has poor water tolerance and oxidation stability. These drawbacks see sodium grease mostly used to lubricate rolling contact bearings. It is often combined with other greases to produce a product of higher value and quality.
Clay grease
Also known as Bentone grease, clay grease is made using bentonite clay. It is often referred to as non-melt lubricant as its dropping point is non-existent. Its key characteristics include protection from wear and tear, temperature change resistance, excellent water tolerance, good shear or mechanical stability, and outstanding adhesiveness. Clay grease is suited to extremely demanding applications and is used in steel production, ceramics, manufacturing, mining, and construction.
Aluminium complex grease
As a lubricant, aluminium complex grease offers many benefits. It can withstand high temperatures and has excellent water-resistance. It also prevents oxidation, rust and corrosion while offering great shear stability. Often, aluminium complex greases are used in the food processing and manufacturing sector, but are also employed in the automotive, construction, steel milling and agriculture industry.
Polyurea grease
Extremely popular because of its impressive characteristics, polyurea grease provides great water resistance, oxidation stability, corrosion and rust prevention, mechanical stability, durability and versatility, along with excellent performance at high temperatures. These features see it recommended for a wide range of long-life applications. Today it is considered critical for the correct lubrication of electric motors and steel plants but is used in many different industries.
Barium complex grease
A high-performance lubricating grease, Barium complex grease is widely recognised for its high-temperature resistance, mechanical stability, ability to cope with high speeds and heavy loads. It also offers exceptional water tolerance and oxidation stability, along with resistance to a diverse range of chemicals. It is mainly used in more demanding and heavy-load applications like marine, industrial, manufacturing, and aeronautical applications.
How to select the right lubricating grease
When ordering the correct grease type for your application, equipment and industry, you must consider these key factors before selecting a product.
Base oil
The base oil is the foundation of the grease and therefore its type will determine the overall performance of a grease. There are three main base oil types – vegetable oils, mineral oils, and synthetic oils. Mineral oil is the most common, but synthetics are considered best in terms of performance, protection, weather resistance, shear stability and temperature. Vegetable oils however offer environmental concerns.
Additives
Additive packages are used to improve the features and attributes of a grease and can boost performance. Common additives include extreme pressure (EP), oxidation, corrosion and rust inhibitors, insoluble solids, polymers for increased adhesiveness, however, additives providing increased protection from wear and tear. Finally, pigments and dyes may be added to grease to colour them.
Thickening agent
Thickeners are employed to enable the ingredients of a grease to bond better, increases the efficiency of the grease overall. Thickener types commonly included are complex and simple soaps, that are lithium, aluminium, calcium, sodium, and barium-compound based. Additionally, certain non-soap thickening agents, like clay or polyurea-based products can be used to supply the grease with its specific consistency.
Viscosity
Lubricating grease viscosity will determine its ability to keep stable and provide effective protection from friction. A higher viscosity delivers greater stability when greases are exposed to heavy and slow loads. In contrast, lower viscosity is greases are suited to higher speed applications.
Consistency
As an attribute, grease consistency has been calculated and set by the National Lubricating Grease Institute (NLGI) and determines the level of hardness or softness of available greases. Each grease product is assigned an NLGI number that ranges between 000 and 6. These grades then express the consistency level of a grease.
With a diverse selection of greases currently available to order, selecting the correct product can feel like a minefield. However, providing that you carefully consider the above factors while keeping in mind the needs of your equipment, operating conditions, and work rates you’ll be sure to pick the right solution.
To make an informed decision, always consult your original equipment manufacturers (OEM) recommended grease or consult your leading lubrication distributor for advice.
