Bearing Failure and Wear: What are the Causes?

Bearings are amazing things and they are everywhere--from the most complex machinery to the simplest child’s toy.  Rule of thumb: If it moves, it probably has some type of bearing.  

Most bearings do eventually wear.  How fast and how much they wear depends on a lot of things such as the type of bearing, the bearing’s material, and operating conditions.

The primary cause of bearing wear—assuming they are properly lubricated--is particles. One study on bearing failure suggests 70% of bearing failures are due to surface deterioration (15% from corrosion/chemical wear and 55% from physical wear). The most common forms of physical wear are adhesive wear (much of which is caused by improper lubrication) and abrasive wear (predominantly caused by particulate contamination).

                Somewhere between 80% and 90% of all bearings are grease lubricated. Studies conclude that inappropriate lubrication and particulate contamination account for 44% to 59% of failures in grease lubricated bearings. There are other, lesser causes such as incorrect installation (alignment or balance issues), overloading, stray current, etc.

                So how can you tell if a bearing is starting to wear?  Well in the Eurofins TestOil lab, analysts may detect metal particulate in the lubricant. While  Elemental Spectroscopy and Ferrous Wear Concentration cannot differentiate metals resulting from corrosion versus physical wear,  Analytical Ferrography can.

Because the most common type of bearing material is AISI 52100 Alloy Steel, which is about 97% iron and about 1.45% chromium, analysts will likely see a sharp increase in iron once the bearings start to wear. But that iron may be from the shafts, gears, lobes, etc... that the bearings are supporting.

Hydrodynamic bearings at constant speed are definitely the least susceptible to wear; the best example being the tilted-pad axial thrust bearing at the Holtwood Generating Station in Pennsylvania, which has been running continuously since 1912 and may last about 1300 more years before it wears out.

Proper lubrication (the right amount and right viscosity) supports bearing clearances to prevent adhesive wear and two-body abrasive wear—more on that later. Stay tuned for a new post that digs deeper into bearing lubricants and lubricant testing!

            For more information on working with Eurofins TestOil for oil analysis and training visit Contact: 216-251-2510;

                With more than 30 years of experience in the oil analysis industry, Eurofins TestOil, focuses exclusively on assisting industrial facilities with reducing maintenance costs and avoiding unexpected downtime through oil analysis program implementation. As industry experts in diagnosing oil-related issues in equipment such as turbines, hydraulics, gearboxes, pumps, compressors and diesel generators, Eurofins TestOil provides customers with a guarantee of same-day turnaround on all routine testing. Eurofins TestOil PRO certified lubrication professionals educate the industry on oil analysis through public and private onsite training. These highly experienced professionals provide a variety of onsite services; from collecting oil samples to conducting failure analyses to writing work orders. For more information on partnering with Eurofins TestOil on oil analysis programs or training opportunities visit Contact: Michael Barrett 216-251-2510;

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