Good machines can last a lifetime. However, it can be nearly impossible to find replacement parts for older equipment and bearings may be discontinued. So what do you do when looking to replace hard-to-find bearings and related parts in older machines?
Application changes affect bearing design
We rarely encounter a bearing that was incorrectly designed in an application, but it is possible that factors within the larger application could change.
How long a bearing lasts before failing is known as the bearing's life cycle. It is generally considered in terms of hours and is based on load and speed conditions.
Overloading and premature bearing fatigue are often the result when loads become too high. Sliding and improper loading of rolling elements occurs if they are too low. These problems also occur with inadequate internal authorization. In all these cases, the result will be early failure.
First signs of failure
Don't ignore the first signs of bearing failure, especially unusual noises or temperature rises.
Abnormal bearing sounds are indicative of specific problems in the bearing application. For example, hearing a buzzing or roaring sound, where the volume and tone change with speed, indicate problems such as poor adjustment, warped bearing rings, vibration of the races, balls or rollers, and brinelling. Grinding or howling sounds often indicate excessive internal play or poor lubrication in a cylindrical roller bearing. The squeaking sound that is heard when the shaft is turned manually usually indicates contamination of the tracks.
A desirable bearing temperature is less than 100 C. At start-up, the temperature will rise, but then stabilize at a slightly lower temperature than at start-up, but somewhere between 10 and 40 °C above ambient temperature. Rising temperatures are another early sign of bearing failure.
Operating stresses in applications can also affect bearing life. It is essential to isolate vibrations in associated equipment, as they can cause irregular operation and unusual noises.
Better bearing performance
What do you do if performance is less than ideal? Lubrication plays a vital role in bearing performance. Grease is the most used lubricant because it is easy to handle and simplifies the sealing system. The oil is most suitable for high speed or high temperature operations.
There are a few ways to improve bearing performance for a specific application. One effective way is through lubrication, specifically the use of high-quality synthetic greases and solid lubricants found in the bearing cavity. What many don't realize is that it is important to use grease/lubrication that has a lifespan equal to or better than that of the bearing. If the grease or lubrication used does not have the same potential lifespan as the bearing, the bearing will fail before its expected lifespan. Replacing the grease with a high-quality lubricant will greatly improve the performance of your bearings and extend their life.
Another way to improve bearing performance is to upgrade it to a bearing made from higher quality material.
The manufacturing and automotive industries still use standard type bearings in terms of shell dimensions. But what has changed is the range of material options. Several industries have upgraded from traditional 52100 chrome steel to various styles of stainless steel, ceramic and even titanium breeds in severe applications with great results.
Asking the right questions is critical when addressing the issue of bearings not meeting expectations. Is there a lot of tension on the bearing? Is the operating temperature too high? Is the rotation delayed? We often find that by upgrading the bearing itself to a higher quality one or by improving lubrication, we can improve operating accuracy, reduce operating temperatures and improve overall performance, extending bearing life.
