Classification of greases for bearings

I Classification by Thickener Type (The most core classification method)

The thickener acts like a sponge, adsorbing the base oil within it to form a paste-like structure. It determines the heat resistance, water resistance, mechanical stability and compatibility of the grease.

 

1.Lithium-based grease

Features: The most versatile and widely applied. It has good mechanical stability, water resistance, rust prevention and medium temperature resistance.

Common types

General-purpose lithium-based grease: Meets the lubrication requirements of most bearings at normal temperature and medium and low speeds.

Extreme pressure lithium-based grease: Added with extreme pressure anti-wear additives (such as molybdenum disulfide), it is suitable for bearings under high load or shock load.

Complex lithium-based grease: By combining with other acids, the dropping point (up to over 260℃) and high-temperature service life have been significantly improved, and its performance is superior to that of ordinary lithium-based grease.

Application: It covers over 80% of conventional bearing lubrication scenarios, ranging from household appliances to industrial motors and automotive wheels.

 

2.Polyurea grease

Features: Excellent high-temperature long-lasting performance, oxidation stability and long service life. It has a high dropping point, no metal ions, and can inhibit the oxidation of base oil. It has good noise performance, but the cost is relatively high.

Application: Motor Bearings (especially high-efficiency motors and variable-frequency motors), bearings in high-temperature areas of steel mills, and precision bearings that require long lubrication cycles.

 

3.Calcium-based grease

Features: Excellent water resistance, but poor temperature resistance (dropping point about 80-100℃), and average mechanical stability. It is gradually being replaced by lithium-based esters.

Application: It is commonly used in damp, low-speed and light-load environments, such as agricultural machinery and water pump bearings.

 

4.Calcium sulfonate-based compound grease

Feature: "All-round" high-performance grease. It integrates extreme pressure and wear resistance, water resistance, rust prevention, high-temperature stability and corrosion resistance, and even has self-healing ability. It is an emerging high-end product.

Application: Bearings for harsh working conditions, such as those in metallurgy, mining, papermaking, offshore platforms, and other heavy-duty, humid, and corrosive media environments.

 

5.Bentonite-based grease

Features: Inorganic thickener, no dripping point, good high-temperature resistance (depending on the base oil), but poor mechanical stability and may fail when exposed to water.

Application: It is used in high-temperature and low-speed environments, such as bearings of certain baking equipment.

6.Aluminum-based grease

Features: Good adhesion and water resistance, but poor mechanical stability and not heat-resistant.

Application: Mainly used for low-speed bearings in ships, maritime equipment and other devices that are in long-term contact with water.

Ii. Classification by base oil type

Base oil is the part of grease that truly plays a lubricating role, accounting for about 90%.

 

1.Mineral oil-based grease

Features: Low cost, balanced performance, and the widest application. However, its high-temperature, low-temperature performance and oxidation stability are not as good as those of synthetic oil.

Application: Most general and conventional working conditions.

 

2.Synthetic oil-based grease

Features: Uses PAO (polyalphaolefin), ester oil, etc. as base oils. It features a wide temperature range (good low-temperature starting performance and strong high-temperature stability), long service life, low volatility and excellent oxidation stability.

Common types

Pao-based lipids: With excellent comprehensive performance, they are the mainstream choice for high-performance synthetic lipids.

Ester oil-based greases: They are often used in situations where there are special requirements for material compatibility.

Application: Extreme temperature environments (such as cold regions, high-temperature kiln cars), high-speed bearings, long-life maintenance-free bearings, and precision instrument bearings.

 

Iii. Classification by Performance and Additives

Additives are used to enhance or endow grease with certain specific properties.

 

1.Extreme pressure anti-wear grease

Features: It is added with extreme pressure agents such as sulfur, phosphorus and chlorine, or solid anti-wear agents such as molybdenum disulfide and graphite, which can form a protective film under high loads.

Application: Heavy-duty gearbox bearings, rolling mill bearings, mining machinery bearings.

 

2.High and low temperature lipids

Features: Utilizing synthetic base oil and compound thickener, it ensures no hardening at extremely low temperatures and no loss or coking at extremely high temperatures.

Application: Aviation bearings, special vehicle bearings, refrigeration equipment bearings.

 

3.Anti-rust and anti-corrosion grease

Features: It has been added with powerful rust inhibitors and passivators.

Application: Bearings in Marine environments, chemical corrosive environments, or equipment bearings that need to be stored for a long time for backup.

4.Food-grade grease

Features: All ingredients comply with food safety standards such as NSF H1, and are non-toxic and odorless.

Application: Bearings for food processing machinery, pharmaceutical machinery, and beverage filling lines to prevent product contamination.

Iv. How to Choose the Right Bearing Grease?

When making a choice, the "STAMP" principle should be comprehensively considered:

 

S-Speed (Speed) : The higher the rotational speed, the lower the viscosity of the base oil, the better the mechanical stability and the softer the consistency should be selected to reduce the heat generated during stirring.

 

T - Temperature: The working temperature range determines the type of base oil (mineral oil/synthetic oil) and the type of thickener.

 

A-Application /Ambient: Is there any water, dust or chemicals? This determines the requirements for water resistance, rust prevention and corrosion resistance.

 

M-Load (Load) : Extreme pressure anti-wear grease should be selected for heavy loads or impact loads.

 

Period (Lubrication cycle) :If you wish to extend the grease change cycle or achieve maintenance-free operation, you should choose long-life synthetic oil-based grease or polyurea grease.

 

The selection of bearing grease is an art of balance. From the economically universal lithium-based mineral oils to the high-performance polyurea/complex calcium sulfonate synthetic oils, their classification systems directly correspond to different working conditions and challenges. Correct selection is a key link to ensure the reliability of bearings and extend their service life.