I want to learn how to use technical calculation tool for service life.
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Technical calculation for Service life
Required service life
Enter the required service life of the bearing.
Using a bearing with too long service life is not necessarily economical.
The required service life would better be set in consideration of the machine on which the bearing is to be used or of operating conditions.
The following table shows required service life used for calculation. The figures have been obtained from experience.
| Operating condition | Application | Recommended service life (h) |
|---|---|---|
| Short or intermittent operation | Household electric appliance, electric tools,agricultural equipment, heavy cargo hoisting equipment | 4000 - 8000 |
| Not extended duration, but stable operation required | Household air conditioner motors,construction equipment, conveyers, elevators | 8000 - 12000 |
| Intermittent but extended operation | Rolling mill roll necks, small motors,cranes | 8000 - 12000 |
| Motors used in factories, general gears | 12000 - 20000 | |
| Machine tools, shaker screens, crushers | 20000 - 30000 | |
| Compressors, pumps, gears for essential use | 40000 - 60000 | |
| Daily operation more than 8 hrs. or continuous extended operation |
Escalators | 12000 - 20000 |
| Centrifugal separators, air conditioners, air blowers, woodworking equipment,passenger coach axle journals | 20000 - 30000 | |
| Large motors, mine hoists, locomotive axle journals, railway rolling stock traction motors | 40000 - 60000 | |
| Paper manufacturing equipment | 100000 - 200000 | |
| 24 hrs. operation (no failure allowed) | Water supply facilities, power stations, mine water discharge facilities | 100000 - 200000 |
Required safety coefficient
The safety coefficient is designated, based on empirical data, so as to ensure safety in relation to basic static load rating.
Safety coefficient＝Basic static load rating／Static equivalent load
| Operating conditions | fs(min.) | ||
|---|---|---|---|
| Ball bearings | Roller bearings | ||
| With bearing rotation | When high accuracy is required | 2 | 3 |
| Normal operation | 1 | 1.5 | |
| When impact load is applied | 1.5 | 3.0 | |
| Without bearing rotation (occasional oscillation) | Normal operation | 0.5 | 1 |
| When impact load or uneven distribution load is applied | 1 | 2 | |
Lubrication conditions
Lubrication oil conditions used to calculate corrected rating life in consideration of factor aISO are entered here.
| Operating temperature | Enter the temperature of lubrication oil (or bearing) during operation. |
| Kinematic viscosity during operation | Enter the kinematic viscosity of lubrication oil at operating temperature. |
* If kinematic viscosity at operating temperature is unknown, click the "Calculation of kinematic viscosity during operation" button. It enables the entry of kinematic viscosity of lubrication oil during operation.
| Temperature conditions (1) and (2) | Enter any temperature to (1) and (2). However, the two settings should be different. |
| Kinematic viscosity at temperatures (1) and (2) | Enter the kinematic viscosity of lubrication oil at temperatures (1) and (2). |
Operating conditions
Operation conditions for calculation of corrected rating life in consideration of factor aISO are set here.
【日本語を変更したので微調整必要】aISO係数を考慮した修正定格寿命と、旧a23係数を考慮した補正定格寿命を計算する際の使用条件の設定を行います。
Enter the magnitude of load that work on a bearing (radial load and axial load) and bearing rotation speed. (To calculate these loads, refer to category 3.2 of the "Bearing info.")
(To calculate these loads, refer to category 3.2 of the "Bearing info.")
Generally, loading conditions are not always constant; they fluctuate in many patterns.
To take account of these fluctuating loads, enter the conditions according to the number of such variations (variation patterns).
How long the individual operating conditions are used should also be considered. Enter at what ratio each condition is used in operation.
Life modification factor for reliability a1
Reliability is "the percentage of the number of bearings that attain a specific life or that are expected to exceed this life in relation to the total number of identical bearings tested through operation under the same conditions." Values of a1 used to calculate a modified rating life with a reliability of 90% or higher (a failure probability of 10% or less) are shown below.
| Reliability (%) | Lnm | a1 |
|---|---|---|
| 90 | L10m | 1 |
| 95 | L5m | 0.64 |
| 96 | L4m | 0.55 |
| 97 | L3m | 0.47 |
| 98 | L2m | 0.37 |
| 99 | L1m | 0.25 |
| 99.2 | L0.8m | 0.22 |
| 99.4 | L0.6m | 0.19 |
| 99.6 | L0.4m | 0.16 |
| 99.8 | L0.2m | 0.12 |
| 99.9 | L0.1m | 0.093 |
| 99.92 | L0.08m | 0.087 |
| 99.94 | L0.06m | 0.080 |
| 99.95 | L0.05m | 0.077 |
(Citation from JIS B 1518:2013)
Contamination factor ec
If solid particles in the contaminated lubricant are caught between the raceway and the rolling elements, indentations may form on one or both of the raceway and the rolling elements. These indentations will lead to localized increases in stress, which will decrease the life. This decrease in life attributable to the contamination of the lubricant can be calculated from the contamination level as contamination factor ec.
Dpw shown in this table is the pitch diameter, which is expressed simply as Dpw = (D + d)/2.
For information such as details on special lubricating conditions or detailed investigations, contact JTEKT.
| Contamination level | ec | |
|---|---|---|
| Dpw ＜ 100mm | Dpw ≧ 100mm | |
| Extremely high cleanliness: The size of the particles is approximately equal to the thickness of the lubricant oil film, this is found in laboratory-level environments. | 1 | 1 |
| High cleanliness: The oil has been filtered by an extremely fine filter, this is found with standard grease-packed bearings and sealed bearings. | 0.8～0.6 | 0.9～0.8 |
| Standard cleanliness: The oil has been filtered by a fine filter, this is found with standard grease-packed bearings and shielded bearings. | 0.6～0.5 | 0.8～0.6 |
| Minimal contamination: The lubricant is slightly contaminated. | 0.5～0.3 | 0.6～0.4 |
| Normal contamination: This is found when no seal is used and a coarse filter is used in an environment in which wear debris and particles from the surrounding area penetrate into the lubricant. | 0.3～0.1 | 0.4～0.2 |
| High contamination: This is found when the surrounding environment is considerably contaminated and the bearing sealing is insufficient. | 0.1～0 | 0.1～0 |
| Extremely high contamination | 0 | 0 |
(Citation from JIS B 1518:2013)
For those who have trouble slecting bearings
If you are not sure what bearing to choose,if you want to change to a more suitable bearing,Please contact JTEKT.
