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.

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.

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)
			Static		Dynamic		Pneumatic
1,78	2,362	2,489	1,422	1,524	1,549	1,600	1,626	1,651
2,62	3,556	3,683	2,083	2,210	2,286	2,362	2,388	2,438
3,53	4,750	4,877	2,794	2,997	3,099	3,175	3,226	3,277
5,33	7,137	7,264	4,267	4,521	4,674	4,801	4,902	4,953
6,99	9,525	9,652	5,588	5,893	6,147	6,274	6,426	6,477

Encapsulated O-Ring, capsules thickness

Section (mm)	Thickness FEP capsule (mm)	Section (mm)	Thickness FEP capsule (mm)
1,78	0,203	5,70	0,508
2,00	0,203	6,99	0,508
2,40	0,254	8,00	0,508
2,62	0,254	8,40	0,508
3,00	0,254	9,50	0,508
3,53	0,305	10,00	0,508
4,00	0,305	12,00	0,762
5,00	0,381	18,00	0,762
5,33	0,508	20,00	0,762

Encapsulated OR

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Encapsulated O-rings, ideal in hostile environments

Fitting of Encapsulated O-Ring

Installation on a rod

Encapsulated O-Rings, table of tolerances

Encapsulated O-Ring, capsules thickness