Bearing failure can grind your operations to a halt, resulting in significant lost time and production. Here are the last three of our six common factors that can cause bearings to fail, and what you can do to prevent them.
By Jerry Rhodes, General Manager of Engineering Fundamentals & Physical Testing, The Timken Company
Edited by Mike Santora
#4: Contamination. Even the tiniest of foreign particles can interfere with the lubrication that enables a bearing to function as intended. There are a number of contamination sources, depending on the application. Shop dust, sand, fine metal particles from nearby machining, water and dirt can all interfere with the lubricant that keeps a bearing operating, and can damage the bearing itself. Particles rolling through the bearings and rolling elements will cause premature damage, increasing stress and shortening overall bearing life.
The best protection against contamination is a proper seal, which must be matched with the given application to offer the best possible performance. This information should be available through the bearing manufacturer. Generally, seals should be regularly checked for hardening and cracking around the radial lip; they should be replaced as soon as possible if any visible damage is detected.
Contamination can occur at other points in the bearing lifecycle. Technicians should routinely test oil and grease samples for solid particles. Additionally, when bearings are removed for inspection, technicians should make sure to wash, dry and then coat bearings with the appropriate preservative before packing away, using the proper storage techniques.
#5: Overloading. Bearings are designed and engineered to operate at specified loads, and when pushed beyond those limits, trouble can occur. Overloaded bearings can fracture components, and left unchecked can lead to more serious damage or consequences.
Like overheating, warning signs of overloaded bearings should be monitored constantly. Abnormal noises and vibrations, overheating, the presence of metallic chips in lubricant filters, and overall diminished performance of the bearing can all indicate that a bearing is operating beyond its load limits. The higher the overload, the greater the damage. Other indications include the fatigue, pitting or flaking away of bearing materials, roller fracture, peeling, and potential plastic deformation or subsurface fracture of the rolling elements or raceways.
#6: Corrosion. Bearing applications in harsher industrial environments are more susceptible to corrosive damage caused by rogue fluids or corrosive atmospheres that can interfere with the protective lubricant. Corrosion can lead to wear, which can, in turn, lead to bearing failure.
Like overloading, subpar performance due to corrosion can often be detected by increased vibration and noise during operation. Corrosion can be identified by reddish and brown discoloration found on the bearings and raceways—not to be confused with the discoloration caused by overheating. Ensuring the use of proper seals and that those seals are not damaged, is one of the best ways to prevent corrosion on the bearing and raceways. External seals can also be used in more extreme environments if necessary.
Thorough documentation of your bearing installation and maintenance processes can help ensure technicians are being diligent in their monitoring of these common causes of bearing failure. Recordkeeping can help identify trends in bearing performance, forecasted maintenance, and the length of service intervals. Include date, equipment model and serial numbers, bearing assembly and serial number, and the bearing’s manufacturer in your documentation.
In many cases, bearing damage can progress over time. Periodic or continuous condition monitoring (vibration, temperature, lubricant sampling, etc.) can aid equipment and process operators define trends over a bearing lifecycle. Establishing specific operating limits can help define the most appropriate interval for bearing replacement.
Armed with this information, more informed decisions can be made to ensure operations keep your business running smoothly, efficiently and profitably.
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