Machinery Lubrication

Machinery Lubrication July Aug 2013

Machinery Lubrication magazine published by Noria Corporation

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Page 57 of 60

BACK PAGE BASICS Lip Seals vs. Labyrinth Seals Shaft seals must be properly selected and maintained. Some seals do a good job of retaining oil or grease but do a lousy job of excluding contamination. Lip seals are a prime example, particularly the ones that are only directed inward. These types of seals tend to wear after a period of time because they make rubbing contact with the shaft. Eventually, the seals no longer function well from the standpoint of both oil retention and contaminant exclusion. very small number make it through the entire length of the seal. A variety of different labyrinth seals are available, from bronze and stainless steel to plastic. The construction of the seals may even change between brands, with some employing magnets and others simply using O-rings to provide the necessary seat for the housing and shaft. However, they all operate on the same principle and must be properly installed to work correctly. When looking for options to boost reliability and minimize bearing failures, consider the seals that are in use. In areas of high airborne particulate matter or heavy washdown areas, a labyrinth-style seal can help limit the ingress of contaminants and prolong machine life. With proper lubrication and contaminant-exclusion devices, many bearings can come close to achieving their design life. References Lip Seal Labyrinth Seal On the other hand, a labyrinth seal is non-contacting, so it will not have the wear-out condition. These seals are excellent for excluding particle contamination and moisture, even if there's a spray of water nearby. So both oil retention and contaminant exclusion are at a much higher level of performance compared to contacting mechanical seals and lip seals. Of course, the disadvantage of using labyrinth seals is that they are more expensive. Generally, you will need to retrofit these on the equipment and will incur the cost of their installation. However, labyrinth seals will last longer and perform better. 56 | July - August 2013 | EG&G Sealol, "Seal & Survive," Seal School Handbook, Revision 3. Fitch, J.C., Scott, R., & Leugner, L. (2012), "The Practical Handbook of Machinery Lubrication — Fourth Edition." Inpro/Seal, "Bearing Isolators." Maintenance Technology (1991), "Beyond Predictive Maintenance." Neale, M.J., "Drives & Seals: A Tribology Handbook." About the Author Wes Cash is a technical consultant with Noria Corporation. He is a mechanical engineer who holds a Machine Lubrication Technician (MLT) Level II certification and a Machine Lubricant Analyst (MLA) Level I certification through the International Council for Machinery Lubrication (ICML). Contact Wes at

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