We’ve previously outlined the basics of lubricant shelf life in the Mobil SHC Club, but we wanted to revisit this important topic to provide some more detail around why shelf life matters and how to catch some early indicators of lubricant deterioration.
Before we begin, it’s important to note that there is a fundamental difference between product life in storage and product life in service. During storage, the packaged product generally remains motionless for extended periods and can be exposed to cyclic variation in temperature and other environmental conditions such as vibration. In turn, these conditions can potentially impact the components of the formulation or potentially allow ingress of contaminants from the environment — both of which have the potential to affect the product’s performance characteristics.
For these reasons, shelf life is a key consideration in inventory-management practices for packaged lubricating oils and greases. Its proper management can help ensure that the lubricants will be suitable for use in-service, delivering performance as promised in the intended applications.
Shelf life defined
As we shared in our earlier post, shelf life is the recommended maximum period a lubricant product in its original sealed container can be stored prior to service in a particular piece of equipment. The lubricant manufacturer typically determines this guidance.
Shelf life recommendations apply to lubricants that have been stored in their original, sealed containers under proper conditions. However, at the end of the shelf life period, ExxonMobil recommends laboratory testing (recertification) to ensure that the product will continue to provide the promised performance in the intended application.
Normal shelf life lubricants
Most lubricants classify as “normal” shelf life products. The recommended shelf life for these oils and greases is typically five years when stored properly in the original sealed containers.
But there are a few visual signs that may indicate lubricant degradation during the storage process.
For example, industrial oils may show deterioration by one or more of the following visual indicators:
Greases may show deterioration in one or more of the following ways:
Excessive oil separation. Some “bleed” is normal and required, but excessive separation could indicate an issue.
Significant change (>25%) in the grease consistency as measured by worked or unworked penetration. Grease consistency affects the ease of grease application, low-temperature performance, and stay-put performance, all critical characteristics ensuring proper grease lubrication. In technical terms, grease’s consistency is referred to as its NLGI Grade — from NLGI 000 (semi fluid) to NLGI 6 (very firm).
Significant change in color or odor
Noticeable change in texture
If any of these signs are present, operators should work with their lubricant manufacturer or distributor to determine if lubricant deterioration has in fact occurred.
Short shelf life lubricants
Water-based lubricants and formulations sensitive to moisture or those with high additive levels are typically classified as having a “short” shelf life. For these products, the container label is usually stamped with a “use by” date. If these types of lubricants are to be used after the noted “use by” date, you should first recertify them to confirm quality and suitability for use. The shelf life stamped on a container label is the official shelf life designation for that container of product. Because of new formulations or field experience, posted shelf life in a list format may change. Therefore, always use the shelf life identified on the label.
The water-based lubricants described here include metalworking coolants and fire-resistant hydraulic fluids. These fluids gradually change and eventually become unusable. Generally, they will destabilize if frozen.
Evidence of deterioration may include one or more of the following signs:
Change in texture
Change in odor (offensive or pungent)
Separation of the oil and water phase
Moisture-sensitive or high additive content products include soluble oils, and indications of deterioration with these products may include one or more of the following signs:
As mentioned previously, operators should work with their lubricant manufacturer or distributor if any of these signs are observed.
If you have any additional questions about shelf life or storage management practices, don’t hesitate to reach out via our “Ask the Expert” button or in the comments section below.
Often customer needs shelf life documents to clear the older stocks or slow running stocks.
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