Bearings are as varied in design as the machines in which they are installed. There are a number of contributors to premature bearing failure. Misalignment and improper lubrication are the two major factors. Misalignment contributes to approximately 1/3 of all bearing failures.
There is a misconception in industry that the use of flexible couplings eliminates the need for precision shaft alignment. Flexible couplings are actually designed to allow machines to operate within in proper shaft alignment tolerances other than “zero”, which is not a practical or possible alignment goal in most industrial applications.
When two machines are misaligned the flexible element of a coupling creates forces at the coupling which are exerted on the shafts and bearings of the machines. These excessive forces contribute to early bearing failure. The goal of precision shaft alignment is to reduce these forces to enable bearings to last their designed L10 life (number of hours a bearing is designed to last).
Improper lubrication contributes to roughly 1/3 of bearing failures as well. Whether the lubricant is grease, oil, or oil mist the proper application of lubricants are essential. Over lubrication can lead to premature bearing failure just as readily as under lubrication. Good lubrication practices include, and are not limited to, maintaining reservoir oil levels, use of the correct lubricant, regular oil and filter changes, oil analysis as needed, and proper venting of grease after application.
Improper bearing installation also leads to premature bearing failure. Many a bearing are damaged before being placed into operation. Bearing manufacture guidelines should be followed during installation for proper use of bearing heaters, installation tools and practices.