Several black or red encapsulated O-Rings overlaying each other.

All FEP Encapsulated O-Rings available from Ashton Seals are produced using the very latest technology and employing the most stringent quality control procedures to provide a pure, seamless encapsulation. They combine the benefits of a Viton® or Silicone elastomeric rubber with the chemical resistance and mechanical properties of Teflon® FEP/PFA polymer. The result being a chemically inert and sanitary assured O-Ring seal designed to overcome common sealing difficulties associated with it.

  • Hostile Chemicals - Chemical attack and swelling are the primary cause of O-Ring failure. FEP polymer also has an extremely low coefficient of friction (.1 to .2) and very low permeability to gases, making Chem-Rings a virtually universal seal for use in hostile environments.
  • Wide Temperature Ranges - Even at -60°C to +260°C, Teflon® Encapsulated O-Rings withstand the most volatile media.
    Sanitary Requirements - The outer clear FEP/PFA Teflon® tubing is specified to be manufactured from FDA, Sanitary 3A & USP Class VI compliant materials.
  • Compression Set - A common bi-product when utilising Solid PTFE/Rubber O-Rings. FEP/PFA Encapsulated O-Rings prevent premature compression set, due to the protection of the FEP/PFA Teflon® encapsulation and retained elasticity of the Silicone or Viton® core.
  • Expensive Perfluoroelastomers - Encapsulated O-Rings provide an economical alternative to expensive Perfluoroelastomers, such as Kalrez® and therefore, vastly increase profitability.

Summary - FEP/PFA Encapsulated O-Rings offer far superior performance to solid PTFE O-Rings as these routinely suffer from ‘Compression Set & ‘Coldflow’. Near universal capabilities at a fraction of the cost of expensive Perfluoroelastomer alternatives and a one material replacement to the various common elastomeric O-Rings. (which will fail or suffer performance degradation in severe environments).

Typical Applications

FEP Encapsulated O-Rings are an inexpensive solution to many critical sealing applications, such as:

Several black or red FEP Encapsulated O-Rings arranged on a metal surface.Industrial Applications:

  • Paper & Pulp Industry
  • Dairy & Beverage, Wine/Beer Industry
  • Oil Extraction (On Shore & off Shore)
  • Cosmetics & Perfumery
  • Food & Drink Processing
  • Automotive Components
  • Scientific Glassware Instruments
  • Computer Chip Manufacturing Industry

Example Applications:

  • Reusable Syringes
  • High Purity Water
  • Gas Service
  • Cartridges
  • Glass Flanges
  • Low Pressure, Quick Disconnect Piping System
  • Vacuum Service
  • Glass Heat Exchanger Tube/Tubesheet Seals
  • Large Diameter Access Covers
  • Relief & Emergency Valves
  • Mixers & Vessels
  • Spray Paint
  • Photoelectric Work
  • Tank Cars & Trucks [Diffuser In Tank)
  • Filter Elements
  • Butterfly Valves
  • Air Operated Vents
  • Scientific Laboratory
  • Lab Reactors
  • Sampling Monitors [Pesticide & Personal Impactor]
  • Manways [T Bolt Hinge Closure]
  • Leak Free Bottles
  • Petroleum Mixers
  • Industrial Concrete Sprayer
  • Stainless Steel Gas Line Holders
  • Flowmeter
  • Chimney
  • Bulkhead Fitting
  • Turbines
  • Magnetic Vacuum Breaker
  • Strainers
  • Pressure Pots
  • Home Irrigation Turf & Auto Control
  • Vessel Lids

Manufacturing standards and quality

The Encapsulated O-Ring consists of a seamless and uniform Teflon® encapsulation, which completely encloses the core material of Silicone or Viton®. The nature of the moulding process is critical to the quality of the Ring. Standards for the manufacture of moulded rubber O-Rings call for close tolerances on the I.D.’s and particularly, the cross sections of the rings. Outside these tolerances any step in the cross section can severely affect the O-Rings ability to seal.


An arrangement of FEP Encapsulated O-Rings on a white background.

Encapsulated O-Rings are available with FEP or PFA Teflon® polymer encapsulation. The capabilities of these two polymers are essentially similar, except that PFA exhibits better heat resistance once above 200°C. FEP Encapsulation is the preferred standard for all applications below 205°C, continuous temperature. Core materials are either DuPont Viton® or High Temperature Silicone.

FDA Compliant

The FDA/PFA Encapsulation of the TEFLON® Encapsulated O-Ring complies with Part 177 of title 21 of the F.D.A. Regulations, for safe use as articles (or components of articles) for producing, manufacturing, processing, preparation, treating, packing, transport or holding food in accordance with F.D.A. Regulation 21 CFR 177.1550.

Minimum I.D. Sizes

Virtually any size of I.D. or cross section of ​Encapsulated O-Rings can be made using existing stocks of material. The only possible normal limitation is the minimum size of I.D. that can be physically encapsulated without kinking. This varies with the cross section of the ring and developments in manufacturing methods.
The table below shows our Minimum Possible I.D.'s at the time of writing. Those dimensions shown in the Special Production columns have increased lead-times and prices, compared to the standard production sizes, due to the increased complexity of manufacture.

A group of red and black FEP Encapsulated O-Rings on a metal surface, with lighting focused on the middle and shadows visible.
Minimum FEP I.D. (mm)
Silicone Viton Silicone Viton
9.50 9.25 36.00
6.00 6.00 50.80 60.00
6.07 6.07 50.80
7.59 9.20 57.00
9.20 10.00 70.00
9.20 12.30 130.00
18.00 18.00 150.00
18.00 20.00 203.20
20.00 20.00 228.60
20.00 27.00 400.00
27.00 35.00

For information on lead times please contact our sales team on 01226 273700 or ask@ashton-group.co.uk.

Viton® is a registered trademark of DuPont Dow Elastomers. If you require genuine DuPont Viton please specify this to our sales team.

Teflon® is a registered trademark of DuPont Dow Elastomers. 

Kalrez® is a registered trademark of DuPont Dow Elastomers.