Introduction
The ability to accurately calculate the lifespan of bearings is an important skill for any engineer. It is essential to properly consider the effect that load, rotational speed, lubrication, and other related factors have on the bearing’s operation.
Bearing life is typically expressed in millions of revolutions (MRs), where MR is an estimate of the number of revolutions the bearing can withstand before failure. The life of a bearing can be estimated using a variety of mathematical algorithms and statistical methods which account for different conditions, such as load, speed, bearing design, and environmental conditions.
Load and Rotational Speed
The load and rotational speed of a bearing largely determine its lifespan. The higher the load, the shorter the life span, while the lower the speed, the greater the life span. Moreover, the higher the speed, the higher the wear and tear on the bearing’s components, which leads to shorter life spans.
When considering the life of a bearing, it is important to note that the static loads which a bearing can withstand are typically higher than the dynamic loads for which the bearing is rated. It is therefore important to factor in both static and dynamic loads when estimating the life of a bearing.
Material
The material from which a bearing is made has a direct effect on its life span. In general, bearings that are made from harder materials such as stainless steel or carbon steel have longer life spans since they can withstand more load and wear better. Conversely, those constructed from softer materials such as brass, bronze, and aluminum, tend to have shorter life spans since they are more prone to wear.
Lubrication
Lubrication is critical to the long-term performance of any bearing. Poorly lubricated bearings are more susceptible to wear and have shorter life spans, while properly lubricated ones tend to have better wear resistance and longer life spans.
Some types of lubrication that are commonly used with bearings are oil, grease, and dry film. Oil is generally the most effective option and provides the most protection, while grease tends to offer the shortest life span. Additionally, dry film lubrication offers much improved wear and friction resistance, however it makes the bearing more difficult to clean and service.
Environmental Factors
The environment in which a bearing is operated also has an impact on its life span. Contaminants such as dust, dirt, and water, as well as extreme temperatures, can all shorten the life span of a bearing. Dirt and dust are typically the most damaging, since they can cause gritty particles to accumulate in the bearing’s components.
Conclusion
Accurately predicting the life span of a bearing requires a thorough consideration of multiple factors including load, rotational speed, material, lubrication, and environmental conditions. Bearing life is typically expressed in millions of revolutions, and depends partly on the expected load and speed of the bearing. Harder materials and proper lubrication are essential for proper bearing operation and longer life span. Furthermore, bearings should be kept in clean and dry environments in order to provide the longest possible life span.
