Extend bearing life with proper handling

All bearings are very precise mechanisms that, in many cases, have geometrical tolerances measured in millionths of an inch. When handling, inspecting or mounting bearings, one should treat them as precision instruments. Most bearing failures are caused by the user’s poor handling techniques.

Foreign particulate matter entering a bearing shortens its life and provides one or all of the following unsatisfactory operating conditions:

* Increased noise

* Increased friction

* Ball skidding

* Increased heat

* Reduced lubricant life.

Keeping the external surfaces and contiguous components (i.e., shafts and housings) contamination-free is also important. Contamination on bearing faces or mating shoulders of the housings or shafts will cause a bearing pair to be out of parallel. This will cause the balls to run in a non-circumferential plane within the raceways, causing ball speed variations, ball skidding and binding between the races. These factors increase friction, which produces heat. Heat causes the lubrication to oxidize, resulting in premature bearing failure.

Follow these proper handling techniques for longer bearing life in your operations.

1. Bearings should never be handled with bare hands. Talc-free finger cots or talc-free surgical gloves should be worn.

2. Work areas must be clean, clean, clean (no food or smoking should be allowed).

3. Bearings should be kept in their original packaging until the moment that they are ready to be installed.

4. Do not clean housings and shafts with shop rags or cotton swabs, as these items usually will contribute to contamination. ‘Clean Room’ wipes or swabs should be used.

5. The use of laminar flow workstations is strongly recommended.

6. Bearing worktools must be kept clean and burr free.

7. Bearings must be kept clear of any source of magnetism.

8. Bearings should be kept in a dry environment, as they are susceptible to corrosion. Moisture and acid from the hands can cause a bearing to corrode.

9. Bearing mounting tools should assure that the bearings are mounted squarely on the shaft and into the housing.

10. Bearings should never be subjected to shock or impact load. Normally, a bearing will become brinelled (dents in the raceways) if dropped from the workstation to the floor, or if it is hammered into place.

11. When press fitting a bearing, force should be applied only to the ring that is being fitted. For example, if press fitting a bearing onto a shaft, force should be applied to the face of the inner ring only. Under no circumstances should the force be applied in a manner such that it is transmitted from one bearing ring to the other through the balls.

12. When handling miniature bearings, external garb (caps, shoe covers and smocks) made of a suitable lint-free plastic yarn should be worn. The use of cosmetics or face powders should not be allowed. Bearings should be stored in their original containers. Never leave them exposed to the environment in uncovered containers.

Lubrication is another important concern when dealing with bearings. Recently, we asked some customers to run accelerated life tests on their products using bearings that are lubricated with a factory grease lubricant, such as those supplied by Chevron, Shell, Mobil or Exxon, to name a few. The average life was recorded.

Additional testing was conducted with new bearings lubricated with the same type of grease with one exception — the grease was ultrafiltered through a three-micron membrane. This process assures that the largest particulate matter was 34 microns diameter or less.

The life of the product using the bearings with the ultrafiltered grease was be two to three times longer, and some customers reported up to six times the life of bearings, compared to those that were tested with grease that was not ultrafiltered.

These tips were provided by AST Bearings, Montville, N.J. For more information, visit www.astbearings.com.