Using the wrong grease is a common cause of premature bearing failure. To choose correctly, you need to understand the three components of a grease and how to read the parameters on its technical data sheet (TDS).
What is lubricating grease made of?
- Base oil: makes up most of the mass and is the component that does the actual lubricating.
- Thickener: holds the base oil like a “sponge” and determines heat resistance, water resistance and adhesion.
- Additives: antioxidants, rust inhibitors, extreme pressure (EP) and anti-wear additives, and solid lubricants such as MoS₂ and graphite.
NLGI consistency grade
NLGI classifies grease consistency from 000 (very soft, almost fluid) to 6 (very hard). NLGI 2 is the most common grade for rolling bearings. Soft grades (0, 00, 000) are used in centralized lubrication systems and grease-lubricated gearboxes. Harder grades (3) are used for high-speed bearings or vertically mounted bearings.
Base oil: mineral or synthetic?
Mineral base oils perform well in most ordinary applications at a reasonable cost. Synthetic base oils (PAO, ester, silicone, PFPE) offer a wider temperature range, better oxidation resistance and longer relubrication intervals. Base oil viscosity also matters: high-speed bearings need a low viscosity, while heavily loaded, slow-speed bearings need a high viscosity.
Common thickeners
| Thickener | Main characteristics |
|---|---|
| Lithium, lithium complex | Multipurpose, widely used; the complex type has better heat resistance |
| Calcium complex, calcium sulfonate | Good water resistance, high load capacity |
| Aluminum complex | Water-resistant, good adhesion; food-grade versions available |
| Polyurea | High-temperature resistance, long service life; used for electric motor bearings |
| PTFE | Very high temperatures (combined with PFPE oil), chemically inert |
Note: do not mix greases with different thickeners without first checking their compatibility, as the grease may soften, run or bleed oil.
Special requirements
- Food, beverage and pharmaceutical industries: use NSF H1-registered grease at points where incidental contact with the product is possible.
- Shock loads, low speeds: choose a grease with EP additives or solid lubricants.
- Humid or water-flooded environments: prefer water-resistant greases with good adhesion.
Dong Tam is an authorized distributor of Bechem (Germany), supplying a full range of lubricating greases and industrial oils for every application.
Need specific advice for your plant? Contact Dong Tam for support from our engineers.