How can you create a system where you know your bearing lubricant is operating efficiently? Getting the right answers is critical to extending bearing life and performance. We begin this 9-part series by detailing bearing cleaning procedures. We’ll follow with proper fill quantity and other factors that will boost your bearing performance.
The removal of any existing oils, greases and anti-corrosion coatings increases in importance as the operating life and reliability of the application becomes more and more critical. The wetting of the contact surface by the lubricating film will be enhanced by a clean contact surface. Removal of these oils, greases and coatings will also eliminate any potential incompatibilities that may exist between these products and the subject lubricant. It is always advisable to remove these materials prior to applying silicone or perfluorinated based products.
Existing surface coatings can act as separating agents, preventing the applied grease from wetting the bearing balls and races properly. For applications that operate in the high speed range (nDm > 800,000 or n/ng* > 0.8), or when a specialty lubricant is being used, a clean dry surface may be critical to ensure the proper adhesion between the grease thickener matrix and the bearing surfaces.
Many bearing companies provide their products pre-coated with an oil film and/or anticorrosion coating. If this coating has both a micro-thickness and is compatible with the chosen lubricant, then a pre-cleaning may not be necessary. It is important to discuss this situation with the subject bearing and lubricant supplier.
Use of a non-residual solvent for the cleaning of bearing surfaces provides the optimum lubrication condition. Prior to selecting a suitable industrial solvent, it is important to refer to any applicable federal, state, local or global regulations regarding their restrictions or proper use.
The most efficient non-residual solvents were CFC-113 (Freon® TF) and methyl chloroform (1,1,1 Trichloroethane). However, restrictions on ozone depleting chemicals prohibit the use of these solvent types. In this case, the best allowable nonresidual solvent should be used.
The application criteria, along with the degree of contamination, will determine the extent of cleaning and whether multiple cleanings or ultrasonic cleaning is necessary.
As the cleaned parts dry, they become prone to atmospheric corrosion. If immediate lubrication is not possible, the parts should be coated with a dispersion of the intended lubricant prior to storage. Even if the bearings are immediately lubricated, the “non-lubricated” surfaces are still prone to corrosion. Therefore, it is advisable to apply a light anti-corrosion coating to these bearing surfaces after lubrication.
* n = bearing rpm, ng = speed rating of bearing using grease (rpm)
What bearing lubrication challenges do you face? Let us know in the comments below.