Grease is a common lubricant for rolling bearings. Once the bearing is installed in the shaft system, it needs to be lubricated properly and during its operation, lubrication needs to be replenished.
Therefore, whether it’s equipment manufacturers or equipment users, they all purchase a certain amount of grease. The storage of grease is a matter of great concern for bearing users. Here are some important points to keep in mind when storing grease:
Maintain Cleanliness
When grease operates inside a bearing, the oil film primarily serves the function of lubrication. Generally, the oil film thickness of a rolling bearing is only a few micrometers, which is quite small, typically smaller than the size of common contaminants.
If contaminants enter the grease, they may cause oil film breakdown during bearing operation, thereby disrupting the lubrication provided by the grease. Therefore, cleanliness should be maintained throughout the usage of grease.
Ensuring cleanliness during grease storage primarily involves the storage environment. A clean environment can help reduce the possibility of grease contamination.
Additionally, the packaging of unused or partially used grease must be kept intact. Unused grease should be promptly sealed to avoid prolonged exposure to air, minimizing the chance of dust particles in the air entering the grease.
Avoid Moisture Ingress
Lubricants should not be exposed to moisture. The ingress of moisture severely affects the lubricating properties of the grease, and can sometimes even alter its inherent characteristics. When storing grease, the first thing to ensure is that the packaging does not get wet from rain, and certain moisture-proof measures need to be taken.
Common methods include adding partitions or cardboard in the storage layer to absorb moisture, and implementing moisture-proof measures in the warehouse to reduce ambient humidity.
During the use of grease, one must also avoid the ingress of moisture. A common scenario is the impact of air condensation. This phenomenon is very common in the north. A temperature difference between the grease and the air can condense moisture from the air onto the grease, thus dampening it.
Therefore, before opening the grease seal, consider temperature factors and carry out appropriate temperature equalization.
Avoid Oxidation
Grease is a chemical product. If not sealed properly during storage, or if exposed to oxygen for extended periods, it may oxidize. Although many greases have antioxidants added, it is still recommended to avoid long-term exposure to air.
Avoid Sun Exposure
Grease should not be exposed to sunlight for extended periods during storage. Sample greases displayed in stores should be replaced monthly to avoid prolonged direct sunlight.
Grease Storage Temperature
The generally recommended storage temperature for grease is between 10°C and 25°C. This temperature range is suitable for long-term storage of grease. Additionally, the temperature at which grease is stored should not fluctuate frequently.
Thickeners and base oils are the primary components of grease, and temperature fluctuations can cause the base oil to separate from the thickener. Frequent temperature changes can impact the performance of the grease.
Packaging and Handling of Lubricating Grease
Lubricating grease often comes in pre-made packaging, each of which is well-sealed prior to opening. It is generally recommended for users to choose smaller packaging whenever possible to prevent spoilage due to poor sealing of unused grease.
For barrel-packaged lubricating grease, it should be stored upright whenever possible. During transportation, care should be taken to avoid inverting or rolling the barrel. This is because inverting or rolling the grease barrel could potentially allow air bubbles to enter the grease. Once air bubbles have entered the grease, it becomes difficult to thoroughly remove them.
If grease containing tiny air bubbles is injected into a bearing, it could possibly cause micro-detonation, thereby damaging the bearing.
Similarly, for toothpaste-like grease packaging, it is sufficient to promptly screw on the cap after use, without the need to refill with air. This not only prevents air from entering the grease but also minimizes contact between the grease and oxygen.
Shelf-Life of Lubricating Grease
There isn’t a unified standard for the shelf-life of lubricating grease, it is typically based on the warranty information provided by each manufacturer. Under standard storage conditions, lubricating grease generally has a long lifespan.
However, differences in storage conditions and the chemical composition within the grease can lead to variations in its shelf-life. Unopened grease can typically be stored for about 5 years, while opened grease should be used within roughly two years.
However, these are merely empirical figures and cannot represent the specific situation for every type of lubricating grease.
