OEB’s many years in the bearing industry have shown that bearing failure often leads to shaft damage. In many cases signs of bearing failure are difficult to detect, which often makes it almost impossible to predict the exact moment of bearing failure. This is particularly true on long conveyors where monitoring is difficult.
There are many reasons why bearings fail, but that is a subject for another article. In this publication, we want to consider and discuss the final stages of bearing failure, which is usually cage failure. We also explain how we at OEB have developed a sealing solution to mitigate premature bearing failure.
Once the cage fails, the rolling elements are no longer guided and disperse in all directions at the bottom of the housing. As soon as the rolling elements stop rolling, sliding friction occurs, flattening the rollers and the shaft starts dropping down. The shaft eventually makes contact with the cast iron housing in the seal area, causing damage to both the housing and the shaft.
The pictures below show the shaft damage in the seal area where the shaft made contact with the housing.
In many cases it is difficult or impossible to replace the shaft. A new bearing is then fitted to the damaged shaft. You now have a large gap between the shaft and the housing, resulting in ineffective sealing and allowing dirt to enter this gap and causing premature failure of the new bearing.
Whilst visiting TRONOX with our distributor, Bearings Distributors Weskus in the Western Cape,we had a discussion with Herman Zandberg, the Mechanical Supervisor, who was lamenting shaft damage as depicted above on his conveyors. Herman remarked that it was strange that there was no seal on the market that could prevent such damage.He remarked that it was strange that there is no seal on the market to prevent this type of damage.
This remark prompted us to discuss the problem with our customers. Almost all our customers had the same problem! We then turned to our own Sales Engineers who often assist with fitting the first Split Roller Bearings we supply. They confirmed that they had seen the same shaft damage.
Based on these discussions with our customers and engineers, we started testing various sacrificial seal materials on our test rig. We removed the cage and rollers from the test bearing and ran the shaft on the seals, thereby simulating a bearing failure. Through these tests we developed a sacrificial seal carrier that provides effective sealing, yet in the event of failure, the seal carrier would wear away without damage to the shaft. At slow speeds (100RPM), like a conveyor, the sacrificial seal lasted many hours before wearing away. At high speeds (1000RPM), typical of a fan, the wear was quick. However, in all cases there was no shaft damage.
This provides the end user with invaluable extra time to spot and address a failed bearing before shaft damage occurs, potentially reducing unforeseen expenses dramatically.
In addition to this innovation, our engineers subsequently fitted the Split V-Ring seal in an attempt to improve bearing life. Our results were very promising.
Our Split V-Ring Seal is held in place on the shaft by a cable tie. The lip runs against the side of the housing, preventing dirt from entering this space. It is important to remember that whilst this is very effective against premature bearing failure, with time the lip wears off and needs to be replaced regularly. A minor cost compared to bearing failure.
In the past our opposition copied all our highly successful designs, namely our “SN” and “SD”, followed by the “SNQ” and “SDQ”. This time we have globally patented our design. Our patent covers Split Roller Bearings, as well as Plummer blocks, since we believe that there will be a demand to retro-fit these seals into existing housings, as well as new housings.
For more information or quotations, please contact Nica Smith - firstname.lastname@example.org