One of the most important things which is recommended to be done before installing most types of seals is to be properly lubricated. Lubricants are commonly used for handling O-rings and other elastomeric seals. Using a suitable grease or oil during installation helps protect the O-ring from damage by pinching, abrasion, or cutting. It also helps seat the O-ring properly, speeds up installation operations, and makes automated assembly line procedures possible.
An additional benefit is the protection that the lubricant provides as a surface film on the O-ring. Furthermore the proper lubrication helps protect some polymers from degradation by atmospheric elements such as ozone. A lubricant is essential in pneumatic applications requiring dynamic service. In vacuum applications, appropriate lubricants help reduce the overall leak rate by filling the asperities of the groove’s metal surfaces and lowering permeation rates of the elastomer. Many sealing situations call for the minimization of frictional forces created by a seal. One of the methods of minimizing O-ring friction is to introduce a lubricant. This lubricant can be of three general types:
Internal O-ring Lubricant
A lubricating agent is mixed into the elastomer before molding. This lubricant is dispersed evenly throughout the rubber before vulcanization and lowers the coefficient of friction of not only the surface, but the entire rubber part. An example of an internal lubricant that is commonly added to elastomers is the Teflon.
Temporary External O-ring Lubricant
A lubricating agent, generally a liquid, is applied to the surface of a molded part. This lubricant generally sits on the surface of the seal, and as such it can be removed by particular fluids or solvents. Temporary external lubricants can greatly reduce abrasion, pinching, and cutting during installation and assembly. An added benefit of temporary external lubricants is that they can act as a barrier between harmful system chemicals and the elastomer, increasing its useful service life. An example of a commonly used temporary external lubricant is petrolatum. It should be noted to that compatibility testing should be conducted before the use of a particular lubricant. Some lubricants can cause swelling of the rubber seal material and degrade its physical properties. An example of such chemical incompatibility is the silicone lubricating oil which causes swelling of the silicone seal.
Semi-Permanent Lubricant Coatings
Some applications may require a lubricant, but temporary lubricant greases would contaminate the assembly. For such applications different types of coatings are available that can provide good lubrication to seals without the contamination issues associated with temporary external lubricants. The term semi-permanent is used because these coatings can peel and flake over time, so they are not totally permanent. Two common semi-permanent lubricants are parylene coating and Teflon coating.
Even just with a basic knowledge of lubricants, it can be seen there are quite a few advantages of using the proper lubrication agent for seals. Higher efficiency, longer life, and better reliability of bought products are goals that every company strives to achieve. Learning more about proper lubricants and applying everything learned will make these goals easily within reach.
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