Choosing the right lubricant for car bearings

  

Bearing failure can be much more expensive than the cost of buying a new bearing. Maintenance costs and production losses due to machine failure can add up quickly. Improper or insufficient lubrication is a major cause of bearing failure, which can lead to contamination or excessive heat build-up. During operation, bearing balls and rollers cause friction due to sliding between the rolling elements and the bearing ring. The contact area of pure roller movement is relatively small compared to the sliding contact area. The lubrication applied between these surfaces increases the life of the bearing and minimizes the heat caused by this sliding friction. Excess heat can damage the surface or break the shelf due to extreme stresses...

 

 

 

Selection of grease lubricant for lubrication of bearings
Grease is a relatively solid semi-liquid product of a thickening agent combined with a lubricant. The lubricant may be a mineral oil, ester, organic ester, glycol or silicone. The thickening agent may be soap (lithium, sodium, barium, calcium or strontium), inorganic non-soap (microgel, carbon black or silica gel) or organic soap (urea compound, terephthalate or organic dye). Most bearing greases consist of a soap thickener with a petroleum oil. Lithium based greases are very popular as bearing greases due to their water resistance and high and low temperature performance. Greases consisting of synthetic lubricating fluids perform well in very low and high temperature ranges.

Grease concentrations vary from a semi-liquid similar to a viscous oil to a solid that is almost as hard as soft wood. By rotating the bearing and cutting the grease, the consistency of the grease may change. This will increase the temperature and soften the fat. Grease consistency is measured by hardness tester. A hardness tester is a tool that drops a weighted cone on a grease sample and measures the depth of penetration. The National Lubricating Grease Institute (NLGI) provides standard grease consistency grades. Advances in grease technology have helped increase the popularity of pre-lubricated bearings. One of the factors of grease bearings that should be considered is the starting torque, especially at low temperatures. Cold grease may resist starting torque. This is more a function of individual grease properties than grease consistency. A good rule of thumb is that grease life is halved with a 25°F (14°C) rise in temperature and doubled with the same drop in temperature.