Encapsulated O-rings, ideal in hostile environments
Encapsulated O-Rings consist of a seamless and uniform PTFE encapsulation which entirely encloses a VMQ-made or FPM-made core. They combine the resilience and sealing force of an elastomer with the chemical resistance of PTFE. This produces an elastomeric PTFE ring with high sealing capability.
Unlike traditional O-rings, encapsulated O-Rings are resistant to solvents and are chemically inert (except for attack by alkaline metals, fluorine and some halogenated compounds at high temperatures). In addition, they have a great resiliency substantially equal to those of elastomers and FEP has a very low friction coefficient. Last but not least, their gas permeability is very low.
This is why we highly recommend their use in chemically hostile environments.
Encapsulated O-rings, seals details
|Encapsulated O-Rings||Material||Temperature [ºC]||Check stock|
|FPM + FEP||-20 to +205|
|EPDM Peroxide + FEP||-30 to +130|
|VMQ + FEP||-60 to +180|
|VMQ + FEP||-60 to +180|
Fitting of Encapsulated O-Ring
To minimize the potential damage to encapsulated OR during its fitting, it is essential to get it done it with total care since approximately 90% of the detected trouble are due to improper installation or housing design mistakes.
Installation on a rod
To insert an encapsulated OR to an internal groove can be quite complicated as it is about the seal to collapse into a smaller diameter than the gland it is being fitted into. Therefore, in order not to damage the seal during its installation, we highly recommend pre-heating it in hot water (60 °C – 70 °C) for ten minutes.
It is important to replace the shaft immediately while the seal is still warm and flexible.
Installation on a piston
The correct fitting of an encapsulated OR to a solid piston head groove can be eased by using a fitting cone. In this case as well, our advice is to pre-heat the seal by immersion in hot water in order to gain elasticity.
Anyhow, in both cases, the seals can be damaged or broken. Unlike standard rubber O-Rings, encapsulated O-Rings cannot be stretched which makes their installation more difficult. And a bad installation may have serious failure consequences.
Encapsulated O-Rings, table of tolerances
Encapsulated O-Rings are usually fitted in the same housings than standard O-Rings so that tolerances are strictly the same. We recommend to use the table here below to build housings according to BS 1806 Imperial Standard
|Section||Width (mm)||Height (mm)|
Encapsulated O-Ring, capsules thickness
|Section (mm)||Thickness FEP capsule (mm)||Section (mm)||Thickness FEP capsule (mm)|