Full definition
Bearing grease is a semi-solid lubricant essential for the effective operation of rolling bearings in various industrial applications. It is composed of a base oil, thickener, and various additives that enhance performance characteristics. The base oil provides lubrication and can have a viscosity grade ranging from ISO VG 32 to ISO VG 460, which is crucial for maintaining the correct flow characteristics under different temperature and load conditions. The thickener, which can be lithium complex, polyurea, or barium soap, plays a vital role in ensuring the grease retains its consistency and does not run or drip away from the bearing surfaces. Lithium complex greases are commonly used for general applications, capable of performing well at temperatures up to 130°C, making them suitable for many standard operations.
Polyurea greases are formulated for high-speed applications and can withstand temperatures up to 150°C, making them ideal for electric motor bearings where high RPM is present. Barium soap greases are typically water-resistant, providing additional protection in environments where moisture exposure is a concern, such as in marine or washdown applications. The NLGI grade (National Lubricating Grease Institute) measures the consistency of the grease, with grades ranging from 0 (very fluid) to 3 (very stiff), with NLGI 2 being the most commonly used grade in general-purpose applications. A recommended general-purpose grease for various industrial applications is lithium complex NLGI 2, with a base oil viscosity of VG 100-150, which provides a balanced performance in terms of lubrication and protection.
The DIN 51825 standard outlines the classification of lubricating greases intended for rolling bearings, ensuring compatibility and performance expectations across different applications. It’s crucial for maintenance engineers and procurement managers to select the appropriate grease for specific applications to avoid premature bearing failure and ensure optimal performance. Brands like SKF, Mobil, and Shell are recognized for their high-quality bearing greases, with products such as SKF LGMT3, Mobilux EP2, and Shell Alvania being widely used in industrial settings.