FOR EXPOSED CONDITIONS.                                


Dust and water in bearings lead to premature destruction. That's why protection is needed, to prevent penetration of unwanted substances and dirt. This article introduces the centrifugal shaft seal design suited for the toughest of conditions.

Machine Environment

Dusty surroundings are one of the most difficult environments for bearing units. In equipment handling powders or in processes generating dust, the protection of bearings against contamination by fine particles requires special design measures.

Wet environment

Wet environments are even more difficult circumstances for bearings. Moisture in a bearing, whether it is water or a chemical, collects at the bottom of the race and creates an emulsifion when mixed with oil. The roller runs through this emulsion and displaces it, creating conditions for rolling element to come into contact with the race creating wear. Instead of hydrodynamic gliding during the loading cycle, the element rubs or scrapes against the surface. Eventually the surface interaction leads to failure of the race or roller.


Bearings are contained within a housing from which a shaft extends. The shaft entry into the housing offers an opportunity for dust and moisture to enter the bearing. The shaft seal closes the gap between the housing and shaft. Choosing the appropriate shaft seal and seal configuration to protect against the penetration of dust and moisture is critical to bearing life.

Bearing housing seals for dusty environments are traditionally oil seals. NBR oil seals are the most common and allow for some flexing of the shaft. To keep out dust when putting a lip seal into place, ensure the sealing lip faces outward.

The lip oil seal, while selected mainly for sealing the shaft to housing gap, is typically an unsatisfactory sealing device. Over time, the lip causes fretting corrosion of the shaft (the gouge seen under the lip when it slides off the shaft). Moisture on the shaft capillaries is drawn past the lip, and water sprayed directly at the lip seal blows past the seal and into the bearing. Oil seals are rarely replaced in installed equipment even though the seal is a perishable component and should be replaced routinely.

Odoo text and image block
Odoo image and text block

Centrifugal seal

Extreme Bearing feature a specially developed centrifugal seal contained within a housing in order to prevent wear on the shaft through abrasion by an emulsion of sand or dust and water.

Functioning principle

The rubber of the rotor ring clamps around the shaft and is turning with the shaft vertically against the stator ring

Because the lips are vertically positioned against the stator ring, the dirt will be repelled from the sealing lips by centrifugal force. The rotor ring can be moved eccentrically in relation to the stator ring. In this way, the centrufugal seal is able to absorb misalignment of the shaft without wear on the rubber lips.

The grease passes the retaining edge through the lubrication channels under the stator ring and between the two sealing lips and stator ring. The grease ensures that any dirt is flushed away.

The clamping of the rubber around the shaft allows it to be used with the centrifugal seal in assembly to prevent surface damage to the shaft.

Odoo text and image block
Odoo image and text block


The gaps between the lips and the stator of the centrifugal seal must be sealed to keep out dust and water. To improve bearing life for centrifugal shaft seals, use an automatic lubricator. Only a small quantity is necessary when slowly flushed into the bearing cavity to force dust and moisture away from the elements.

Typical Extreme Bearing application with exposure to salt water, a lot of sand and small pieces of shell.



Type-shaft B d1 t b
CS-020 32 32 3 7
CS-025 42 40 3 7
CS-030 47 46 3 7
CS-035 52 50 3 7
CS-038,1 62 60 3 7
CS-040 62 60 3 7
CS-044,45 62 60 3 7
CS-045 62 60 3 7
CS-050 72 70 3 7
CS-050,8 72 70 5 7
CS-055 72 70 5 7
CS-060 82 80 5 7
CS-063,5 82 80 5 7
CS-070 100 100 5 12
CS-075 110 110 5 12
CS-076,2 110 110 5 12
CS-080 110 110 5 12
CS-082,55 110 110 5 12
CS-088,9 130 130 5 12
CS-090 130 130 5 12
CS-100 130 130 5 12
CS-101,6 130 130 5 12
Extreme bearing centrifugal seal built-in dimension