SKFbearing lifeCalculator

Selecting the correct bearing will be determined by its life calculation. It’s not just a matter of selecting the right bearing, but also understanding how long it will be in service. Calculating bearing life enables engineers to predict its useful life. Engineers can be confident that the bearings selected will remain in service providing the optimal  performance.

One way to estimate the effective service life of a bearing is to use the basic rating life calculation taking into account the load and speeds present. The basic rating life is the number of revolutions or operating hours that a group of identical bearings can last before failure.  A failed bearing is evident  when material fatigue occurs on one or both of the rings or rolling elements .

Bearings are crucial components in machinery and equipment that require rotational motion. Bearings are incorporated into rotating parts to reduce friction. The expected life of a bearing under particular operating circumstances can be determined by doing  life calculations.

The speed factor is used to calculate the bearing’s equivalent dynamic load rating (P). The equivalent dynamic load rating is the load that a bearing can theoretically withstand for a million revolutions at the given operating speed. The equivalent dynamic load rating is calculated using the following equation:

The basic dynamic load rating (C) of a bearing is the load that a bearing can theoretically last for  one million revolutions without experiencing fatigue failure. This rating is determined by the size and design of the bearing and is provided by the bearing manufacturer.

To use this formula, the dynamic load capacity and applied load on the bearing must be known. Once these values are determined, they can be used in the bearing life formula to calculate the expected life of the bearing. It is important to note that this formula provides an estimate of the bearing life, and other factors such as lubrication, contamination, and operating temperature can affect the actual life of the bearing.

Bearing lifecalculator

The industry standard for measuring bearing life is the L10 life, which is defined as the number of revolutions or hours of operation that 90% of a large population of bearings will complete before failure, assuming they are all operating under the same conditions. This means that 10% of the bearings in the population may fail earlier than the L10 life, while 90% will last as long or longer.

Generally speaking, the service life of a bearing can be defined as the number of revolutions or hours of operation that a bearing can perform before it requires replacement or maintenance.

The basic principle of bearing life calculations is to conclude that 90% of the bearings will meet or exceed the calculated life while 10 % may not.

The speed factor is an important consideration when calculating the expected life of a bearing. The speed factor is a function of the bearing’s operating speed.

Bearing lifein hours

THE MOST COMMON CAUSES OF BEARING FAILURE AND THE IMPORTANCE OF BEARING LUBRICATION RKB TECHNICAL REVIEW - FEBRUARY 2010 1 The Most Common Causes of Bearing Failure and the Importance of Bearing Lubrication Ciprian Radu RKB Bearing Industries - Advanced Software Engineering Unit Abstract: Bearing failures have great impact on industry and economy. The aim of the present work is to study and spot the major causes that limit bearing efficiency, thus leading to bearing failure. This study shows that the main failure cause is the inappropriate lubrication of the bearing rolling elements (approximately 80% of the cases), followed by inadequate bearing selection (10%), improper mounting (5%), indirect failure (4%), and material defects and manufacturing errors (less than 1%). Key words: Bearing failure, Contamination, Grease, Oil, Lubricant, Lubrication 1. Lubrication of rolling bearings The rolling bearing is a machinery component that plays a very important role, since it dominates the machine performance. If one of the bearings fails, not only the machine, but also the assembly line stops and the deriving costs may be extremely high. For this reason, every bearing manufacturer should make every effort to ensure the highest quality for each bearing and the most careful use and maintenance on behalf of the user [10]. Lubricants are used between contact surfaces to keep the parts in continuous motion. The main purpose of rolling bearing lubrication is to avoid or reduce the metal-to-metal friction between the rolling and sliding contact surfaces. This is not the only function of rolling bearing lubrication. The supplementary functions are: heat dissipation from the bearing, removal of solid wear particles and contaminants from the rolling contact surfaces, corrosion protection, increase of the sealing effect of the bearing seals [4]. Lubrication is crucial for bearing life. In heavy duty applications, such as rolling mill machines, furnaces, ovens or high temperature fans, rolling bearings may be exposed to higher-than-normal temperatures. For these applications, appropriate selection of the lubricant and lubrication method is very important [13]. In industrial applications there are two types of lubricants suitable for high temperature use: grease and oil. In special cases, bearings are lubricated with solid dry lubricants [4]. Grease lubricant is used for 90% of all rolling bearings. The amount of grease to be used will depend on many factors relating to the dimensional and geometrical parameters of the housing, space limitations, bearing working speed and type of grease used. As a general rule, rolling bearings and their housings should be filled from 30 to 60% of their total capacity. If working speed and temperature rise, then a reduced amount of grease should be used. If the amount of grease is excessive, temperature rises, which may cause the grease to soften and local leakage may appear. With the passage of time grease loses its properties and fresh grease must be resupplied at proper intervals. The relubricating interval depends on the bearing type, dimensional parameters, bearing working speed and temperature [10]. In industrial applications, oil lubrication is used if adjacent machine components are supplied with oil as well, or if generated heat must be dissipated by the lubricant. The heat dissipation is necessary if high rotating speeds and/or high loads are involved or if the bearing is exposed to high temperatures [4]. In this case, the relubricating interval depends on bearing operational conditions (temperature, speed, load etc.), oil quantity and type of oil used. If an oil bath lubrication method is used when operating temperatures are around 50 „aC, then the relubricating interval should be one year. For operating conditions of 70 to 100 „aC, the oil should be replaced every three months. Anyway, it is important that lubrication system and deterioration be verified regularly to determine oil replacement [10]. Another type of bearing lubrication is solid or dry lubrication. This method is used in industrial applications, where rolling bearings are subjected to heavy loads, slow relative movements and high working temperature. Solid lubrication is very effective and yields relatively long running times. The most commonly used solid lubricants are graphite and molybdenum disulphide. These solid lubricants are applied to the raceway surfaces in the form of powder loose, sliding lacquer or paste. Graphite and molybdenum disulphide lubricants can be used for high operating temperatures of up to 450 °C [4].

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Bearing life is a key factor to consider when selecting the right bearing for an application. Depending upon the application, the bearing may be exposed to different  loads, temperatures, and speeds. This means that different bearings will provide different levels of life expectancy. It is important to consider the expected life of a bearing before making a selection to ensure it will meet the requirements of the application.

SKFbearing lifechart

Bearing lifemeaning

The scale of bearing life refers to the expected duration of time that a bearing can operate effectively before it needs to be replaced due to wear or failure. Bearing life is typically measured in terms of the number of revolutions or hours of operation before the bearing fails.

Bearing lifecalculation pdf

Regular maintenance and proper lubrication can help to extend the effective service life of a bearing and prevent premature failure.

The speed factor (n x dm) is the product of the bearing’s operating speed (n) and the mean diameter of the bearing (dm). The mean diameter is calculated as the average of the bearing’s inner and outer diameters. The speed factor is expressed in units of mm/min.

Ballbearing lifein hours

THE MOST COMMON CAUSES OF BEARING FAILURE AND THE IMPORTANCE OF BEARING LUBRICATION RKB TECHNICAL REVIEW - FEBRUARY 2010 4 Fig. 7 - Bearing failure due to water contamination a) b) Fig. 6 - a) The frosted appearance of this bearing raceway illustrates what happens when the oil viscosity is too low and metal-to-metal contact occurs. b) Bearing failure due to continual welding contact between asperities on the metal surfaces about the same oil film is built up at different operating temperatures if both oil types have the same viscosity at 40 °C. The diagram in figure 4 and equations (2) and...

THE MOST COMMON CAUSES OF BEARING FAILURE AND THE IMPORTANCE OF BEARING LUBRICATION RKB TECHNICAL REVIEW - FEBRUARY 2010 3 Fig. 5 - Required kinematic viscosity, ƒÞ, at reference temperature Fig. 4 - Reference kinematic viscosity, ƒÞ1, at reference bearing speed and pitch diameter Fig. 3 - Abrasive wear on the outer ring raceway The excessively long time lubrication without renewing and unsuitable lubrication of rolling bearings represent a large percentage of premature bearing failures (approximately 20% each), and in most cases they can be prevented [9]. Unsuitable lubricant is a...

The operating  conditions,  loads , speeds, and  lubrication and bearing precision affect the effective service life of a bearing.

Bearing lifechart

Where X and Y are coefficients that depend on the bearing type and size, Fr is the radial load, and Fa is the axial load. The equivalent dynamic load rating is then compared to the basic dynamic load rating to determine the expected life of the bearing.

THE MOST COMMON CAUSES OF BEARING FAILURE AND THE IMPORTANCE OF BEARING LUBRICATION RKB TECHNICAL REVIEW - FEBRUARY 2010 2 Fig. 1 - Common bearing failure causes 2. The most common causes of bearing failure In practice, damage or failure of a bearing are often the result of several mechanisms operating simultaneously. The failure can result from improper assembly or maintenance or from faulty manufacture of the bearing or of its adjacent parts [3]. In some instances, failure is due to a design compromise made in the interests of economy or from unforeseen operating conditions. It is the...

In general, a bearing’s useful service life is the amount of time during which it can continue to function properly without suffering excessive wear or damage. The number of hours of operation, rotations, or cycles that a bearing operates is used to express the bearing’s effective service life.

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