Do you handle your ball bearings with kid gloves? The way you do makes a tremendous difference.
Daniel Juchniewicz, an applications engineer for SKF Bearings, lists the various times bearings are handled and how important proper maintenance practices matter. And, he writes, those practices start, fittingly enough, at the beginning.
For any bearing used in rotating machinery, applying best maintenance practices and using the correct enabling tools can help contribute to maximum bearing service life. These practices include proper storage and mounting, adequate lubrication, and close monitoring and inspection that can uncover the root causes of any damage. While certain uses will present unique factors that influence a bearing’s service life, several general maintenance rules can preserve the working condition of bearings regardless of the application.
Juchniewicz offers advice for the various stages bearings go through in their life beginning with storage and mounting.
Storing Your Bearings
From the outset, proper bearing storage is critical. Bearings should always be stored in a cool, clean, low-humidity environment that is free of dust, shocks, and vibrations—never directly on the floor. Ideally, bearings should be stored flat, rather than on their end, in their original, unopened packages until mounting. If stored in a standing position, bearings are much more likely to experience false brinelling, the wear of raceways and rolling elements caused by residual vibration.
Proper Mounting Techniques for Bearings
When a bearing is ready to be mounted, maintenance personnel should confirm that both the shaft and housing are clean, undamaged and dimensionally accurate (with proper fit and tolerance). They also must confirm that the lubricant is clean and correctly specified, that the necessary tools and equipment are available and that safety precautions are followed.
Because they are precision components, bearings should be handled and mounted with care, and operators should always use correct techniques and technologies. An estimated 16 percent of all premature bearing failures are caused by poor fitting, usually using brute force and lack of awareness of suitable mounting tools and methods. When mounting a bearing, personnel should never strike it directly with any hard object, such as a steel hammer or chisel, or apply the mounting force through the rolling elements.
According to Juchniewicz, there are two primary ways to properly mount bearings: cold and hot. If the bearings are small or medium-sized, cold mounting is recommended using fitting tools to apply the correct force to both bearing rings, separating the element that roll from the impact force.
If the bearings are larger, preheating the bearings so they expand follows the practice of Hot mounting. Hot mounting provides an easier method of installation and a better fit.
For more information regarding bearing heaters, please read this article from SKF. According to the article, 16% of premature bearing failures are the result of incorrect mounting methods.
One of the most important aspects of healthy bearings is proper lubrication. As we’ve talked about before, the amount and type of lubrication is critical.
Choosing the proper lubricant helps bearings perform as long as intended. Good lubricants primarily provide a separating film between a bearing’s rolling elements, raceways and cages. This lubrication prevents metal-to-metal contact and friction that generate excessive heat, lead to adhesive wear, and cause subsequent metal fatigue and spalling of the bearing contact surfaces. The proper lubrication inhibits wear, corrosion, and contamination damage.
Half of all bearing failures attributed to poor lubrication are caused by the selection of an inadequate grease for the operating conditions or by mixing incompatible greases. The proper grease delivers the necessary base oil viscosity in the proper amount at the prevailing operating temperature. For this reason, the correct type of grease is essential for optimized bearing performance.
Grease has traditionally served as the preferred lubricant for rolling bearings because of its practical benefits. Grease is easy to apply, can be retained within a bearing’s housing and offers protective sealing capabilities.
Maintaining Your Bearings
Juchniewicz goes on to explain the importance to monitor the health and dismount bearings.
Predictive maintenance provides excellent tools to take a snapshot of the health of the bearings. Vibration analysis allows technicians to “hear” possible defects. Laser shaft alignment is an example of a corrective service.
Replacing Your Bearings
Removing old bearings may lead to problems with the replacement bearings if not handled correctly. Improper methods may lead to shaft damages.
A damaged shaft can compromise a machine’s efficiency and greatly influence the service life of the new bearing.
Bearings also may be dismounted for maintenance or replacement of other machine components. Because these dismounted bearings will be mounted again (unless they are damaged during dismounting), personnel should enlist proper dismounting methods and tools. Choice of tools will depend on bearing type, size, and fit.
When a bearing must be replaced because of premature failure, bearing and grease analysis can help determine root causes, which can include inadequate lubrication, contamination, errors in mounting or dismounting, and electrical damage. Pinpointing the actual causes will help prevent a repeat failure.
Regarding your bearing practices, do you have a preferred method for complete maintenance of your bearings?