FEP-O-SEAL® O-Rings

About this product

Technical brochure with information on mounting

These seals ideally combine the elastic characteristics of elastomer O-Rings and the chemical resistance of FEP or PFA. FEP-O-SEAL® O-Rings consist of two components: a seamless covering of FEP or PFA (1) and an elastomer core (2) that guarantees dimensional stability. There are numerous applications where the use of traditional elastomers causes failure. Aggressive chemicals or extreme temperatures can destroy conventional elastomer O-Rings which can ultimately lead to leakage.

• extremely high chemical resistance against most liquids and chemicals • great range of possible operating temperatures from -60°C up to +250°C (depending on the core material) • good resistance to pressure, compression and deformation • low steam permeability and minimum water absorption combined with low cold flow compared to PTFE • durability and reliable service • saving in maintenance costs • compatibility with foodstuffs • non-adhesive smooth surface

It should be noted, that FEP-O-SEAL®, like all other elastomer O-Rings, are subject to compression set caused by stress and associated material fatigue. FEP-O-SEAL® rings with a small cross sectional diameter have a relatively high compression set. For these reasons, it is important to always use the FEP-O-SEAL® ring with the largest possible cross sectional diameter. We recommend FEP-O-SEAL® primarily for static applications, either axial or radial. For dynamic seals e.g. valve spindles and slip ring seals, FEP-O-SEAL® should only be used if “p – v values” are low and only after preliminary testing.

VMQ Core is well matched for applications that demand lighter compressive forces and higher temperatures. FKM Core is a fluoroelastomer compound with exceptional mechanical properties. The FKM elastomer gives the O-ring a faster recovery rate. CRYOLOX Core stainless steel components are ideal in services such as flowing liquid oxygen and hydrogen with extremely low cryogenic temperatures. FEP encapsulation (fluorinated ethylene propylene) gives the O-Ring its strong characteristics relating to its resistance to nearly all chemicals, liquids and gases. PFA encapsulation (perfluoroalkoxy copolymer) is similar to FEP but with improved cold flow properties and optimized mechanical qualities at higher temperatures.

FEP-O-SEAL® O-Rings are used in a wide variety of applications in many industry sectors, but in particular, where ordinary elastomers fail due to aggressive fluids.

With VMQ solid core approx. 85 – 90 Shore A With VMQ hollow core approx. 75 – 80 Shore A With FKM solid core approx. 90 – 95 Shore A

Inner diameter (d1) mm for cross section (d2) up to 7mm Tolerance mm

The FEP sleeve of FEP-O-SEAL® is very sensible to extrude at pressures above 50 bar (with hollow core type on up to 50 bar). At these higher pressures, back-up rings must be provided. The permissible clearance on the side away from the pressure is given in the table below.

Normally the groove dimensions of elstomer O-Rings are also valid for FEP-O-SEAL®.

FEP-O-SEAL® O-Rings are preferably used as static seals (axial or radial), e.g. for flanges, covers, shafts, pistons, spindles etc. The surface finish of the contact faces and the groove should be as follows:

In the case of flange or cover seals where the groove is axially accessible, there is no need for any special precautions. If the pressure is exerted from inside, the FEP-O-SEAL® should be in contact with the outer diameter of the groove and vice versa, if pressure is exerted from outside, the O-Ring must be in contact with the inner diameter of the groove.

If shafts or pistons are sealed radially, grooves that can be accessed axially should be provided wherever possible. If grooves are not accessible axially, the following mounting instructions should be observed:

1. In the FEP-O-SEAL® O-Ring mounting area there must be no sharp-edged transitions, ridges, machining lines, threads, through holes etc. The slightest damage to the FEP covering causes loss of seal.

Source: Angst+Pfister brochure "FEP-O-SEAL® O-Rings", https://www.angst-pfister.com/dam/jcr:0c02c641-4f36-4fe0-88fb-c90ec24c21f8/FEP-O-Seal O-Rings Version 3.pdf