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Most Frequently Asked Questions About Bearings and Bearing Usage
You can find the explanations for the most frequently encountered questions about bearings and bearing usage, prepared by our experienced engineering team, on this page.
How should the bearing life calculation be made?
After selecting the bearing type, its size is determined either by the static load carrying capacity or the dynamic load carrying capacity. If the bearing operates for long periods or rotates very slowly, it is selected based on static load carrying capacity; if it operates for relatively long periods, it is selected based on dynamic load carrying capacity.
Determining the size based on static load carrying capacity: The static load carrying capacity calculation is based on the concept of the bearing undergoing a permanent deformation under constant load. To compare the applied loads with the load carrying capacity given in the catalog, we need to reduce the radial and axial load effects to a single equivalent load.
The equivalent load for static load carrying capacity (Po) is:
Po = Xo.Fr + Yo.Fa
Where: Fr: Radial load on the bearing, Fa: Axial load on the bearing, Xo: Static radial factor, Yo: Static axial factor,
(Xo and Yo values vary based on the Fa/Fr ratio. Therefore, it is necessary to first calculate the Fa/Fr ratio and then select the Xo and Yo coefficients according to that ratio.) After determining Fr, Fa, Xo, and Yo, the static equivalent load, Po, can be found. Comparing this value with the static load value, Co, in the catalog gives us the safety factor for that load: The Co/Po ratio provides the safety factor for that load.
Determining the size based on dynamic load carrying capacity: The dynamic load carrying capacity is based on the life calculation (not on permanent deformation).
The equivalent load for dynamic load carrying capacity (P): P = XFr + YFa
Where: Fr: Radial load on the bearing, Fa: Axial load on the bearing, X: Radial factor, Y: Axial factor,
Similar to the static load carrying capacity calculation, X and Y values vary based on the Fa/Fr ratio. Therefore, it is necessary to first calculate the Fa/Fr ratio and then select the X and Y coefficients according to that ratio. After determining Fr, Fa, X, and Y, the dynamic equivalent load, P, can be found. Since dynamic loads are based on life calculation, the value C in the catalog shows the load that the bearing can carry for one million revolutions (for 90 out of 100 bearings).
The number of million revolutions the bearing will make at the equivalent load P can be calculated using the following formula:
For ball bearings, L = (C/P)^3 – For roller bearings, L = (C/P)^(10/3)
Where: L: Life in million revolutions, C: (Given in catalogs) dynamic load number, P: (Calculated) equivalent dynamic load,
The lifetime in operating hours can be calculated using the number of revolutions per minute (n) as follows:
Operating hours in lifetime = L * 10^6 / (60 * n)
One of the main factors affecting bearing life is unfortunately user errors. Incorrect bearing selection, assembly mistakes, and inadequate or improper lubrication are the primary causes of user errors. It is important to seek assistance from your supplier regarding the selection and usage of bearings based on the application.
Lubrication performs the following tasks inside a bearing:
If the bearings arrive without lubrication, they must be greased by you.
General Recommendations:
n x dm > 100,000 [min-1 x mm],
Fill 20% to 25% of the space,
n x dm < 50,000 [min-1 x mm],
Fill 100% of the space,
The bearing should be lubricated such that 50% of the space between the housing where the bearing is placed and the left and right sides of the bearing is filled.
The main difference between sealed bearings and open bearings is that the sealed version protects the bearing from unwanted foreign particles. Another advantage of the sealed version can be considered the retention of grease inside the bearing. However, in some versions of sealed bearings that provide contact sealing, the friction causes them to operate at lower speeds compared to the open version, which can be a disadvantage.
Sealed bearings are generally divided into two categories based on the application:
Bearing internal clearance refers to the allowance for expansion due to the increase in temperature at high speeds during operation, as specified by the manufacturer according to a certain standard. In options with a larger internal clearance, less friction occurs, and it is expected to operate at higher speeds. However, for applications where a more rigid system is desired, a lower clearance class may be preferred. Although it can vary depending on the application, it is important to seek support from your supplier regarding this matter.
The key difference between ceramic ball bearings and steel ball bearings is that ceramic ball bearings generate less heat at higher speeds, allowing them to operate more efficiently. However, when considering cost, ceramic ball bearings are more expensive than steel ball bearings.
Depending on the product and application type, they generally have the same load carrying capacity.
The most important feature of the cage in a bearing is to prevent contact between the rolling elements and ensure they move in an orderly manner. However, in some applications, when we want to increase the load carrying capacity without changing the main dimensions of the bearing (inner diameter, outer diameter, thickness), it is possible to remove the cage structure and increase the load carrying capacity by using more rolling elements. The bearing type in which the cage structure is removed and more rolling elements are added is called a full complement bearing. The key difference between these two types is that the full complement bearing has a higher load carrying capacity compared to the caged type of the same size and operates at lower speeds. Although this can vary depending on the application, it is important to seek support from your supplier regarding this matter.
Thin section bearings, which are more commonly found in defense industry and aerospace applications, are used to save space in smaller dimensions and simultaneously meet the same requirements with higher precision due to their geometries and special designs. However, they may come with higher costs compared to standard bearing types. → See: Thin section bearings.
Rail-car and nut-screw systems from different brands cannot work together. The car or nut must be from the same brand as the rail or screw.
In linear bearings, just like in rotary bearings, preload can be achieved with less bearing internal clearance. While the magnitude of the preload varies depending on the application, in principle, a higher preload ensures the bearing moves more rigidly, but it also causes it to operate at lower speeds. It is important to seek support from your supplier to select the correct preload value according to the application.
Bearings that are not subjected to predictive maintenance can often fail suddenly. This can not only damage other components working with the bearing but also lead to hard-to-repair consequences due to prolonged downtimes caused by the failure. Generally, the following conditions and their derivatives indicate bearing damage:
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