Dust and water in bearings lead to early-life destruction. Therefore, protection methods against ingress are needed. This article introduces the centrifugal shaft seal design suited to contaminated conditions.

Machine Environment

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

Wet environments are even more difficult for bearings. Moisture in a bearing, whether it is water or a chemical, sits at the bottom of the race and emulsifies (mixes) with the oil. The roller runs through and displaces the mixture, creating conditions for rolling element to race contact and their destruction. Instead of hydrodynamic gliding through the loading cycle, the element rubs or scrapes against the surface. Eventually the surface interaction leads to failure of  the race or roller.

Bearing Housings

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

Problem definition

The lip seal, while selected mainly for sealing the shaft to housing gap, is typically an unsatisfactory sealing device against wet and sandy pollution. Over time, the rubber is attacked by dirt, water, sand and various other contamination. The pollution goes into the soft material of the rubber and 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. Lip seals are rarely replaced in installed equipment although, as the seal is a perishable component, it should be routinely replaced.

Worn shaft by use normal lipseal
Worn shaft by use normal lipseal
Worn radial seals by contact of abrasive dirt


Extreme Bearing has specially developed the centrifugal-seal for bearing housing sealing against sand and water dust pollution.

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 against the stator ring positioned the dirt will be repelled by the centrifugal force from

the sealing lips. The rotor ring can be move eccentric in relation to the stator ring, in this way is Centrifugal seal is able to adsorb misalignment of the shaft whiteout fatigue of 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 the ingress of dirt is discharged.

The clamping off the rubber around the shaft allows it to be used the centrifugal seal in assembling with light surface damage of the shaft.






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


Built-in dimension Extreme bearing


d1 t
20 32 3
25 40 3
30 46 3
35 50 3
40 60 3
45 60 3
50 70 3
55 70 3
60 80 3
65 100 5
70 100 5
75 110 5
80 110 5
90 110 5
100 110 5