Factors to Consider When Selecting Bearing Grease

Bearing lubrication is a fundamental step in bearing maintenance, with the appropriate grease playing a pivotal role. Equipping bearings with the right grease, in the correct amount, and at the optimal time is crucial when attempting to avoid premature failure in your designs.

The significance of selecting an appropriate bearing grease cannot be overstated, but given the extensive array of lubricants available, finding the right one can be a challenge. Additionally, we know that relubrication with incompatible greases can cause a number of issues and inevitably lead to bearing failure.

Incorporating solid lubricants can take the guesswork out of the bearing lubrication process. Solid lube is an oil-saturated polymer material molded into the interior of the bearing. It fills all internal space without impeding the rolling elements.

Solid lube provides increased protection to the rolling elements by stopping contaminant ingress at the source. It also eliminates leakage – which occurs when oil and thickener separate in grease.

The technology of solid lubrication has revolutionized the industry, providing a more consistent and reliable lubrication mechanism.

A close up photo of two mounted bearing units. The units have had part of their housings and outer rings cut away to show the internals of the bearing. One is empty and one features a fill of solid lubrication.

Choosing the Right Lube

The best lubrication for a particular bearing depends on a number of factors. These include bearing speed, operating environment, and maintenance intervals. It is important to consider all of these factors when choosing a lubricant to ensure that the bearings will operate properly.

Here are some of the factors to consider when choosing a lubricant:

  • Speed: The speed of the bearing will affect the type of lubricant that is needed. High-speed bearings require a lubricant with a low viscosity, while low-speed bearings can use a lubricant with a higher viscosity.
  • Load: Load also plays a part in what lubricant is needed. Heavily-loaded bearings require a lubricant with a high load-carrying capacity and may require special additives. 
  • Temperature: Ambient and operating temperatures are important to consider. High-temperature bearings require a lubricant that can withstand high temperatures without breaking down. Bearings in freezing conditions need a lubricant that won’t become too firm or otherwise ineffective.
  • Contamination: The application’s environment will affect the amount of contamination that the lubricant will be exposed to. Bearings that operate in dusty or dirty environments will require more frequent relubrication intervals, and a lubricant that can resist contamination.
  • Maintenance Requirements: Such as – grease compatibility, greasing quantity, and frequency. Proper cleanliness, and storage are also variables that need to be taken into account.

Understanding the Components of Bearing Grease

The compatibility of different greases are important to consider when choosing a lubricant. If two incompatible grease options are mixed, it can cause serious problems, such as premature bearing failure.

Finding an equivalent bearing grease that aligns seamlessly with the grease you’re replacing might appear to be a daunting task. Nonetheless, it’s a challenge that can be conquered.

Several factors should be taken into account when considering a replacement grease for bearings:

  1. NLGI Consistency: This parameter gauges the hardness of the lubricant, ranging from grade 000 (similar to cooking oil) to 6 (resembling a block of wax).
  2. Base Oil Viscosity: The thickness of the oil used within the grease. The optimal viscosity for your bearing will be determined by factors like operating speeds, temperatures, and bearing dimensions.
  3. Oil Type: Bearing grease can be formulated from natural (mineral) or synthetic oils.
  4. Thickener Type: Thickeners, whether a grease uses simple or complex soaps or non-soaps like aluminum, calcium, polyurea, or lithium, play a significant role.
  5. Additives: These enhance grease performance in specific applications, such as extreme pressure (EP) conditions, rust inhibition, or friction reduction.

It’s important to note that a perfect match across all these elements is not always essential for compatibility. However, if transitioning without fully cleansing the bearing, ensuring that grease thickeners are compatible will yield better outcomes.

A chart that lists common grease thickeners and their compatibility with each other. Some greases are compatible, some are borderline, and some are incompatible.

Consequences of Incompatible Bearing Lubrication

The central goal of bearing lubrication is to shield surfaces and prevent direct contact through the creation of an oil film via the grease. Regrettably, the incompatibility of two grease types can lead to results akin to insufficient lubrication or even serious damage. In severe cases, this can speed up the failure of critical components—a scenario that’s undesirable but preventable.

Some incompatibilities are more conspicuous than others. For example, when dealing with NLGI grade disparities or varying oil viscosities, achieving uniform distribution within bearings becomes challenging. Similarly, an inadequate match between oil viscosities can compromise the protection of rolling elements.

Thickeners within grease help retain the oil, but incompatible thickeners can alter the consistency, causing oil and additives to leach out. This results in ineffective protection and lubrication.

Under certain conditions, the grease might solidify, become overly runny, or leave behind abrasive residues similar to salt. The consequences of such materials in a bearing are easy to imagine.

When making a grease transition, selecting a new grease that is similar or compatible to the previous product minimizes potential conflicts. If this is not possible, thorough purging and cleaning of the bearings may be necessary.

In conclusion, diligent research and consideration are crucial when seeking a compatible replacement grease for bearings. This ensures optimal performance and extends bearing life.

First-hand experiences have shown us how improper lubrication can wreak havoc on rotating components. This often leads to failures that are both costly and time-consuming to resolve.

Solid lube has stepped out as a front-runner because it virtually eliminates bearing failure due to improper lubrication. Ultimately, the right grease for bearings isn’t just a lubricant—it’s a critical investment in the performance, reliability, and longevity of your machinery. 

By researching, and staying informed on the latest options, we can ensure that our equipment continues to operate at its best. This minimizes downtime and maximizes productivity. Bearing lubrication might seem like a small detail, but its impact is anything but minor.

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