There are many misconceptions regarding the “shelf life” of the types of lubricants that are contained in the precision ball bearings that AST Bearings supplies to its customers.

The lubricants that are in the bearings that we supply are high-quality lubricants that are typically qualified to certain military lubrication specifications. The type and quantity of lubricant is in many cases specified by the customer, and in those cases where the customer has not made a particular selection, the bearings would be lubricated to conform to industry standards.

AST Bearings purchases the requested lubricants from a lubricant manufacturer, and then lubricates the bearings accordingly. Regarding the “shelf life” of any lubricant, AST Bearings has to rely upon the recommendations of that particular lubricant’s manufacturer. Our engineering library contains lubrication specification/data sheets, and books describing the attributes of the lubricants offered by most of the world’s major lubricant manufacturers and many of the specialty lubricant manufacturers. It is interesting to note that the majority of these publications convey an absolutely “zero” reference to “shelf life”.

The problem for AST Bearings in addressing the shelf life issue is that AST Bearings simply is not the lubricant manufacturer. It must be emphasized that those lubricant manufacturers who will make recommendations on shelf life will make those recommendations based on shelf life related only to the storage life of the lubricant in the original container. Once the lubricant has been applied to a bearing or other device, factors which the manufacturer can neither predict nor control will govern lubricant life. Therefore the onus falls upon the end user to establish a different data base regarding either storage or operating life.

In order to establish meaningful control procedures at AST Bearings, we elicited the services of a leading “Tribologist” to give us guidance. The advice was that we establish internal control procedures that dictate that we would conduct any age-related testing only after the lubricant or lubricated bearings are at least two years old. This is a scheduled time for testing and does not presuppose that the lubricant has aged beyond its usefulness. It should be noted that any of the lubricants or bearings that we have in stock are inventoried in a controlled environment in sealed containers.

To ensure proper functioning of bearings expired lubricant or lubricant closely approaching its expiration date can often be replaced with newer lubricant.  Sometimes this is cost effectifve, other times it may not be.

To learn more about bearing relubrication services, please visit our section entiteled, "Bearing Lubrication and Relubrication/Re-lube Services"

For an even more in-depth discussion on bearing lubrication, please check out our white paper on bearing lubrication entitled, "Bearing Lubrication - Types, Methods, and Shelf Life"