Bearings are mechanical components that allow moving parts to rotate or move smoother by reducing friction. Bearings of all shapes and sizes are widely used in many diverse industries. Most bearings are usually lubricated with grease and can operate up to a temperature range of 90-100°C.
In certain high-temperature environments, however, standard bearings are unable to fulfill their full-service life. Components such as rubber seals and polymer cages will show signs of failure at around 120°C. At temperatures above 150°C, standard bearings require frequent re-lubrication due to shortened grease life.
Very high temperatures can also cause structural changes to bearings. The clearance of the bearing is reduced and eventually, the bearing is likely to seize. Bearing failures result in frequent machine downtime and unscheduled maintenance, which can incur huge costs.
In industrial applications with extremely high temperatures, such as the metal industry and the food & beverage industry, high-temperature bearings should be used instead of standard bearings.
High-temperature bearings are best suited for use in operations where the environment is hot and dry, with slow rotational speeds.
These specially designed bearings are often lubricated using graphite instead of grease. Graphite is commonly used as a solid lubricant. It can operate in temperatures up to 350°C, making it suitable for use in high-temperature environments. These bearings do not need to be re-lubricated, saving time and costs.
High-temperature bearings are able to reduce your total cost of ownership, through the following ways:
- Increased bearing service life in high-temperature applications
- Fewer maintenance needs can in turn improve productivity and efficiency.
- Food grade variants are available for the F&B industry
- Improved worker safety as manual lubrication in high-temperature conditions can be dangerous.
Fields of Application
- Paint Ovens
- Steel Industry
- Furnaces for Ceramic Industry
- Brick Kilns
Insert bearings and ball bearing units for high-temperature applications
Except for the cage and seals, SKF insert bearings (Y-bearings) for high-temperature applications correspond in design to standard insert bearings with set screws in the YAR 2-2F series. The bearings have a shield and a flinger on both sides to prevent the ingress of solid contaminants into the bearing.
The entire surface of the bearing and the shields are manganese phosphated to enhance adhesion of the lubricant to the metal and improve the running-in properties of the bearing. The flingers are treated by pickling.
The radial internal clearance is a multiple of C5 to prevent the bearings from seizing, even when they cool rapidly.
Bearing benefits and features
The benefits and features of high temperature insert bearings and ball bearing units (fig. 1) include:
- No need for relubrication
All variants are lubricated for the life of the bearing with graphite-based high temperature lubricants.
- Simple replacement
The boundary dimensions are the same as those of standard bearings and units.
- Operating temperature up to 350 °C (660 °F)
The internal radial clearance and the lubricant are optimized for operation at high temperatures.
- Quick and easy mounting and dismounting
The set screws in the inner ring enable quick and easy mounting/dismounting.
- Protection against solid contamination
Shields and flingers (designation suffix 2F) protect the bearing.
- Improved running in
The entire bearing surface is manganese phosphate coated.
- No colour flaking
The housing is coated with a high temperature resistant coating.
Designs and variants
The SKF assortment of insert bearings and ball bearing units for high temperature applications (fig. 2) provides solutions for various combinations of operating temperature and speed.
Table 1 lists the lubrication type, maximum operating temperature, limiting speed, maintenance requirements and all other primary characteristics of the variants within the assortment.
SKF high temperature insert bearings are capped on both sides with a shield and a flinger that create a narrow gap-type labyrinth seal (designation suffix 2F, fig. 2).
The metallic shields and flingers:
- prevent the ingress of solid contaminants into the bearing
- are non-contacting
- generate no friction
- do not wear
- are particularly well suited for high temperatures because of their material and design
Zinc chromate ball bearing unit designs
SKF ball bearing units for high temperature applications are available in three different housing designs: