Engineering Stack Exchange is a question and answer site for professionals and students of engineering. It only takes a minute to sign up.
Sign up to join this community
I have a high speed roller bearing rated at 3000rpm.
I know in the electrical industry that tolerances of around 10-15% are built into components so that they continue working in fluctuating electrical environments.
Is there a similar tolerance in the bearing industry ?
The maximum speed for a bearing recommended by the manufacturer can be due to one of two limiting factors, Thermal, or Mechanical.
The thermal speed rating (often called "reference speed") is calculated using ISO 15312 standardised operating and cooling conditions, and as such, if you are able to provide improved cooling in your application, then, you will be able to exceed this rating.
The mechanical speed limit of a particular bearing should not be exceeded except in very rare cases. If you need a higher speed, then you should look to find a more appropriate bearing specification.
The SKF website says this about operating above the published speeds:
It is possible to operate a bearing at speeds above its reference speed, its adjusted reference speed, or even the limiting speed. Before doing so, first make a detailed thermal analysis, and take whatever further measures may be required, such as use of special cage executions, or consider using high precision bearings. Regarding management of the effects of increased speed, consider the following options:
- Control the resulting increase in bearing temperature by additional cooling.
- Compensate for any reduction in bearing clearance resulting from increased bearing temperature.
- Revise the housing fitting tolerance choice to ensure that the influence of increased bearing temperature does not impair the axial displaceability of non-locating bearing outer rings.
- Revise the bearing tolerance class, together with the geometrical precision of the shaft and housing seats, to ensure these are sufficient to avoid excessive vibration
- Consider using an alternative cage execution that is suitable for higher speed operation, in particular when approaching or exceeding the limiting speed.
- Ensure that the lubricant and lubrication method used are compatible with the higher operating temperature and the cage
execution.- Check that the relubrication interval is still acceptable, particularly for grease lubricated bearings. Oil lubrication may be required.
