Fettning

Fettning, in mechanical engineering contexts, refers to the process of applying grease to bearings, gears, and other moving parts to reduce friction, wear, and corrosion. The practice is widespread in automotive, industrial machinery, and consumer appliances, and is essential for extending service life and maintaining performance.

Grease is a lubricant composed of a base oil thickened with a soap or non-soap thickener. Common thickener systems include lithium, lithium complex, calcium, and polyurea, with mineral or synthetic base oils. The lubricant’s consistency is classified by the NLGI scale from 000 (fluid) to 6 (solid). For many automotive and industrial applications, NLGI 2 grease is standard. Some greases are formulated for food contact (NSF H1) or for high-temperature or high-load conditions, including synthetic or high-temperature thickeners.

Application methods include manual greasing with a grease gun or hand packing, and automated or centralized lubrication systems that deliver specified intervals and quantities. Proper grease selection depends on temperature, load, speed, environmental exposure, seals, and compatibility with materials.

Standards and testing: Greases are specified by regional standards and product datasheets. Key tests include the worked penetration test (ASTM D217) to determine consistency, and tests for dropping point, viscosity, and oxidation stability. The National Lubricating Grease Institute (NLGI) classification and DIN 51825 are commonly referenced.

Maintenance and considerations: Regular inspection for leaks, contamination, and grease degradation is important. Over-lubrication can cause heat buildup and attract dirt, while under-lubrication leads to increased wear. The selection should match operating conditions, and seals and housing must be compatible with the grease.