Sealing technology manual for the process industry - Encapsulated O-rings

ENCAPSULATED O-RINGS Encapsulated O-rings are a combination of an elastomeric O-ring and a closed encapsulation of modified PTFE, which combine high chemical resistance and elasticity in an ex- cellent sealing function. They consist of an elastomer core that provides elastic contact pressure, as well as a jacket for reliable sealing in aggressive media. The core material used is either FKM or VMQ, depending on the required temperature resistance. The encapsulation is made of FEP (fluorinated ethylene propylene) or PFA (perfluoroalkoxy copolymer). Encapsulat- ed O-rings are used exclusively for static applications, since movements or abrasive media would destroy them. Encapsulated O-rings are basically available in all desired dimensions, internal diameters and cord thicknesses – in metric and inch sizes. Since they are only slightly expand- able and compressible, the installation spaces should be designed accordingly, especially for seals with small diam- eters. FEP/PFA encapsulation as well as the VMQ and FKM core are FDA-and USP-compliant as a standard. The different material types affect both the sealing properties and the price level. Thus, PTFE-encapsulated O-rings are less ex- pensive, but must be protected against ingress of media at the seam in terms of their constructional design. Solid PTFE O-rings in contrast are extremely resistant to media but lack elasticity. Function • Elastomer core provides elastic contact pressure • FEP or PFA encapsulation effectively protects the seal against aggressive media Dimensions • All metric and inch cross-sections are available, all stand- ard dimensions are in stock • FEP/PFA O-rings are available in all internal diameters with no additional tooling costs; the smallest possible in- ternal diameter of 1.6 mm is limited by the cord thickness • Pure PTFE O-rings are available in all dimensions, as they are manufactured by machining TYPES FKM core/ FEP encapsulation Very good compression set and permitted temperature range from –20 to +200 °C (–4 to +392 °F) VMQ core/ FEP encapsulation For low temperatures from –60 to +200 °C (–76 to +392 °F) FKM core/ PFA encapsulation For high abrasion resistance and tempera- tures from –20 to +200 °C (–4 to +392 °F) FKM core/ PFA encapsulation For high abrasion resistance and extreme temperature ranges from –60 to +260 °C (–76 to +500 °F) VMQ hollow core For applications in delicate devices and requi- ring little contact pressure For profiles with oval, rectangular or semicircular cross-sections (all with rounded edges), please contact Freudenberg Possible design FEP encapsulation Installation and assembly Inside sealing – grooves in housings: • Seal must be deformed to fit in the housing • To facilitate assembly, soak the ring in hot water for 10 minutes and then immediately fit it into the groove. To do so, push the ring’s leading edge past the groove • Carefully position the ring’s trailing edge in the groove and pull back on the leading edge until the ring snaps into the groove (rod should be inserted while the ring is still warm and pliable) • Use installation aids if necessary Inside sealing – groove in housing Inside sealing – groove in housing Product portfolio 68

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