What is the expected service-life of a fan-bearing? At many plants fan bearing service life is considered good if it is more than two years at the same time life calculations normally show 10 years and more! What if a fan bearing could actually last ten years plus?
The SKF fan shaft solution will enable you to upgrade your fan’s performance to achieve a longer life. The real roadblock to fan speed and performance is excess heat generated by the bearings as a result of speed, load, misalignment, thermal elongation and vibrations.
Industrial fans and blowers also operate under nearly every condition with challenges such as heat, dust, corrosive vapours, and wash-down which shorten their life. What all industrial fans have in common is the need to operate reliably for long periods of time. Premature bearing failure is one of the most common issues facing fans resulting from lubrication loss or contamination, shaft misalignment, or excess vibration. Unscheduled downtime can be very costly with production losses and emergency repairs particularly in the event of a catastrophic failure and where fans are difficult to access.
The modern self-aligning solution
Technology develops, ten years ago there was only one way to accommodate axial expansion of the shaft: allow the non-locating bearing to slide in the housing. Today, however SKF offers an innovative bearing system consisting of two self-aligning bearings: the CARB toroidal roller bearing and a spherical roller bearing.
The CARB bearing combines the self-aligning properties of the spherical roller bearing with the free axial movement of a cylindrical roller bearing with the additional benefit of a lower minimum load rating. By using a CARB bearing in the non-locating position and a spherical roller bearing in the locating position the system accommodates thermal expansion of the fan shaft within the CARB bearing virtually without friction. This system runs with lower friction, temperature and vibration levels, reduces power consumption and enables higher fan speeds.
Housings and seals
SKF SNL, SAF and SONL housings and seals are designed for use with SKF self-aligning bearings, and are suitable for the locating or non-locating positions. They maximize service life by combining stiffness, highly accurate machined surfaces and an ability to draw heat away from the bearing. SNL housings are also available with K7 bearing seat fit for applications prone to vibrations and fretting.
Solution benefits
When compared to the typical self-aligning bearing system, the SKF self-aligning solution provides the following benefits:
- Eliminates the problem of induced axial loads created by thermal expansion of the shaft.
- Reduces friction and vibration levels.
- Decreases heat generated by the bearings.
- Allows use of K7 fit housings to prevent fretting.
- Reduces power consumption for maximum pressure and air flow.
- Enables higher speed due to lower bearing temperature.
On the global scene the total shaft solution is now becoming a new industry standard. Many customers are reporting that they have gone from catastrophic failures several times a year to a situation where the bearings are no more an issue and all service done is the condition monitoring. A paper mill in US changed to CARB set up in 2005 and are still running with the same set of bearings. Swedish energy producer, Fortum, introduced the total shaft solution in 2008 after 2-3 yearly catastrophic failures. After the changeover the fan has not have one catastrophic failure in almost 10 years.
In conclusion most fans should never be in need for replacement bearings at all!
For further information, please contact your local SKF authorised distributor or email customerservice.nz@skf.com
