One significant and challenging issue that MROs and OEMs face is premature bearing failure in equipment. Many require bearings that can stand up to harsh environments, extremely high load capacities and operating where downtime is not an option.
But, what if you are unable to replace that failed bearing or mounted unit (a ball or roller bearing set into a housing) because you’re not sure which bearing you need or are unable to read the numbers on an old, worn or damaged bearing? This happens frequently in the packaging, mining and electric motor repair industries. Not only is the situation utterly frustrating, the extended down time drives up costs, consumes valuable production time and generally throws everything off.
For MRO and OEM, we’ve developed a unique online "Bearing Detective" to help identify the required bearing. This is an easy-to-use program found in the Resources section of our website that asks all the right questions such as: the inside dimension of the shaft; inside dimension of the housing; width (cross section); the bearing style, cage material and more. Our system, along with our expert bearing team, then tracks down the bearing that is needed and calls with an answer within one business day.
Even though our “Bearing Detective” program makes it easy for MRO and OEM to source the required bearing and get operations back up and running, the question remains. How do you reduce the likelihood of bearing failure in the first place?
Avoiding Premature Bearing Failure
In standard applications, a bearing will most often successfully reach its predicted "B10 life", which is known as the point at which 10 percent of a given bearing product is expected to fail. In applications with severe environments, bearings are statistically more likely to fail.
The way in which a bearing fails is often indicative of the cause of the failure. If you know what to look for, symptoms of certain types of failure can be identified before an actual failure occurs. Rust and corrosion, flaking, pitting, unusual wear patterns, creeping and skewing failures are often related and can be corrected once the cause is determined.
Identifying the Cause
Bearing failure may be caused by a number of things, one being improper mounting and installation. Pay close attention to shaft and housing tolerances as if the fit is too tight, you will create too much preload. If the fit is too loose, it creates too little preload and the shaft may rotate or creep in the bearing. Avoid misalignment or shaft deflection. Be sure to use the proper tools, for example, a sleeve to impact the entire Inner Ring Face of the Ring being press fit. Maintain the proper Radial Internal Clearance established in the original design as it allows for lubrication, heat and shaft fit challenges.
Proper lubrication of the bearing ensures the prevention of rust and corrosion, and the reduction of friction and abrasion. Lubrication transports the heat generated by friction, and also keeps foreign objects and contamination away from rolling elements. Lubrication failures occur when there is too little or too much oil or grease, or a mixing of oil and grease. Failure also occurs when the wrong lubricant is used or if there is contamination, such as water or objects, in the oil/grease. Grease is generally used for lubricating bearings because it is easy to handle and simplifies the sealing system, while oil lubrication is generally suitable for high speed or high temperature operations.
If the operating environment is not taken into consideration, lubrication and installation failures will occur. Dust and dirt can aggressively contaminate a bearing, so proper sealing techniques are imperative. This is also the case when there is aggressive media or water. Specialty type seals, such as Pump Mechanical or Labyrinth style seals that do not score the shaft, are recommended.
External heat and current passage (or electrolytic corrosion) are also significant factors of the operating environment. The ambient operating temperature mandates many choices in Radial Internal Clearance, high temperature lubricants, intermittent or continuous running and more which affect bearing life. If current is allowed to flow through the rolling elements, sparks can create pitting or fluting on the bearing surfaces. This should be corrected by creating a bypass circuit for the current or through the use of insulation on or within the bearing.
Still having difficulty determining the cause of that bearing failure? Along with our online “Bearing Detective”, we offer a comprehensive Bearing Failure Analysis guide that details the many ways that bearings can and do fail before reaching their "B10 life". Bearing failure analysis can be quickly performed in-house with this guide, as it enables you to identify the problem with the bearing, determine why it failed and how to correct it. The accurate diagnosis of bearing failure is imperative in the prevention of repeated failures and additional expenses.
Barden Corporation. Machine Tool technical bulletin for Engineering and Lubrication. 2010.
FAG Bearings Corp. Rolling Bearing Damage. Publ. No. WL 82 102/2 December 1997.
Koyo Bearing Corp. Rolling Bearings: Failures, Causes and Countermeasures. Catalog No. 322E. December 1995.
NTN Bearing Corp. Products and Technology. Care and Maintenance of Bearings. 2009.
About the Author: Steven Katz is the president of Emerson Bearing, a leading provider of bearings to Original Equipment Manufacturers (OEM) and Maintenance, Repair and Operations (MRO) markets around the globe, and also president of sister company Action Bearing which serves New England.