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Encapsulated O-Rings

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-RingsMaterialTemperature [ºC]Check stock
Juntas Tóricas EncapsuladasFPM + FEP-20 to +205
Juntas Tóricas EncapsuladasEPDM Peroxide + FEP-30 to +130
Juntas Tóricas EncapsuladasVMQ + 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

SectionWidth (mm)Height (mm)

Encapsulated O-Ring, capsules thickness

Section (mm)Thickness FEP capsule (mm)Section (mm)Thickness FEP capsule (mm)