O-rings

PTFE O-rings are ideal for applications in the chemical, food, pharmaceutical and medical industries. They offer excellent chemical resistance, are physiologically safe and can be sterilised.
They also stand out for a wide operating temperature range from -200 °C to +260 °C and stick-slip-free running.
Data sheet (PDF)
Logos: certified quality, TÜV SÜD, German Federal Ministry for Economic Affairs and Energy, ESF, EU, European Social Fund.
Cross-section of a white PTFE component with horizontal grooves.

O-rings made of PTFE and other high-performance plastics

PTFE O-rings are used mainly in the food and chemical industries, in pharmaceuticals and in medical engineering as static seals on flange connections, covers, etc. Thanks to their good chemical resistance they are compatible with most liquids and chemicals. Exceptions are liquid alkali metals and some fluorine compounds. They are also physiologically safe and can be sterilised. Further advantages are the wide operating temperature range from approx. -200 °C to +260 °C and stick-slip-free running. As they are machined, they can be produced in all dimensions up to a diameter of approx. 1,000 mm.

Application range

Application media

Materials

Materials
CCN-01 (PTFE pure)
CCN-02 (PTFE modified)
PTFE conductive
Typical properties
low gas permeability, universal chemical resistance, good reverse bending strength
very low gas permeability, universal chemical resistance
static dissipative
Operating conditions
standard material, food environments
for enhanced requirements on gas tightness and surface finish
for ATEX requirements (hazardous areas), limited reverse bending strength

Design note

PTFE O-rings can only be stretched or compressed to a limited extent. Due to their low elasticity, the O-ring size must match the nominal dimension to be sealed. They should only be installed in easily accessible split grooves.

Installation recommendations for axial static installation

Sectional drawing of an O-ring seated in a groove between two grey parts, with dimensions B5, T3 and R1.
O-ring Groove dimensions
Cross-section d₂ Groove width B₅ + 0.1 Groove depth T₃ + 0.05 Radius R₁
1,50 1,70 1,30 0,20
1,60 1,80 1,40 0,30
1,78 – 1,80 2,00 1,60 0,40
2,00 2,20 1,80 0,50
2,40 2,60 2,15 0,50
2,50 2,80 2,25 0,50
2,62 – 2,65 2,90 2,35 0,60
3,00 3,30 2,70 0,80
3,10 3,40 2,80 0,80
3,53 – 3,55 3,90 3,15 1,00
4,00 4,40 3,60 1,00
5,00 5,50 4,50 1,00
5,30 – 5,33 5,90 4,80 1,20
5,70 6,30 5,10 1,20
6,00 6,60 5,60 1,20
7,00 7,70 6,30 1,50
8,00 8,80 7,20 1,50
8,40 9,20 7,55 2,00

Slit PTFE O-rings

Since PTFE O-rings are harder than elastomer O-rings, they require higher contact pressures. This can be countered to a certain extent by slit ring designs. The O-ring must always be installed so that the pressure of the medium spreads the slit open.
Slit PTFE O-ring, design I – axial plunge cut, inside.
Design I – axial plunge cut, inside
Slit PTFE O-ring design.
Design A – axial plunge cut, outside
Slit PTFE O-ring design.
Design M – radial plunge cut
Slit PTFE O-ring design.
Design SI – 45° offset plunge cut, inside
Slit PTFE O-ring design.
Design SA – 45° offset plunge cut, outside

FEP-encapsulated O-rings

Depending on the temperature range and medium, FEP-encapsulated O-rings have an elastic core made of FKM or VMQ. The very high chemical resistance of the FEP envelope protects the core material against attack by the medium. (You will find a material overview at the end of this page.) This makes the O-rings ideal for very high chemical and thermal loads while offering the elastic properties of customary elastomers. Mounting requires special care, as FEP can only be stretched or compressed to a limited extent. Its flexibility can be increased by heating it to 80 °C to 100 °C in hot water or oil.
Application range Temperature: -55 °C to +200 °C (depending on core material)

Elastomer O-rings

An elastomer O-ring is a universal seal with many advantages. It combines high sealing performance with a small installation space and low bolt forces. It is used mainly for static applications and is only suitable to a limited extent as a dynamic seal or for linear and rotary movements. Elastomer O-rings are ideal for high pressures and high thermal loads. They show low frictional wear and a long service life. These cost-effective seals are available in various Shore hardnesses and for many media. With little lubrication, stick-slip effects can occur. After long standstill periods there is a risk of sticking, and gap extrusion is possible.

Cross-sections d2 by standard

Standard Cross-sections (d₂) of O-rings in mm
German metric standard DIN 3771 1,00 1,50 2,00 2,50 3,00 3,50 4,00 4,50 5,00 5,50
International standard ISO 3601-1 1,80 2,65 3,55 5,30 7,00
Swedish standard SMS 1586 1,60 2,40 3,00 5,70 8,40
French standard NFT47-501 1,90 2,70 3,60 5,33 6,99
Japanese standard JIS B 2401 1,90 2,40 3,10 3,50 5,70 8,40
American standard AS 568 A / British standard BS 1806 1,78 2,62 3,53 5,33 6,99
American standard AS 568 A series 990 1,02
2,08		 1,42
2,20		 1,63
2,46		 1,83
2,95		 1,98
3,00
Special dimensions O-rings to customer specification – further cross-sections on request

O-ring materials at a glance: standard materials

Designation according to ISO 1629 Base elastomer Trade names Properties
NBR Nitrile butadiene rubber Chemigum®, Buna N®, Nipol N®, Krynac®, Paracryl®, Perbunan N®, Hycar®, Elaprim® -25 °C to +100 °C
A synthetic rubber with excellent resistance to fuels, oils, hydraulic oils, greases and other aliphatic hydrocarbons. Good physical properties such as high abrasion resistance and dimensional stability, and good temperature resistance.
EPDM Ethylene propylene diene rubber Buna AP®, Dutral®, Epcar®, Keltan®, Nordel®, Royalene®, Vistalon® -40 °C to +140 °C
Very good resistance to ozone, ageing and weathering, also resistant to hot water and steam. Good low-temperature resistance compared with other synthetic rubbers. Swells strongly in aliphatic, aromatic and chlorinated hydrocarbons.
VMQ Methyl vinyl rubber / silicone Silopren® -50 °C to +210 °C
Very good temperature resistance. Oil resistance approaches that of NBR, but its good physical and mechanical properties are not reached. Not suitable for continuous use in hot water or steam.
FKM Fluororubber Viton®, Fluorel®, Technoflon® -20 °C to +200 °C
Very good resistance to mineral oils, aliphatic and aromatic hydrocarbons, chlorinated hydrocarbons, concentrated and dilute acids and weak alkalis. High mechanical values, very low gas permeability, excellent ageing resistance and very good compression set.

Special materials (selection)

Designation according to ISO 1629 Base elastomer Trade names Properties
FEPM Tetrafluoroethylene propylene copolymer rubber Aflas® -30 °C to +200 °C
Peroxide-cured TFE elastomer with high resistance to a wide range of specific media and chemicals such as hot water, steam, acids, alkalis, ammonia, bleaches, sour gases (H₂S), oils, amines, additised engine and gear oils, brake fluids and oxidised media.
FFKM Perfluororubber Kalrez®, ZALAK®, PAROFLUOR®, CHEMRAZ®, SIMRIZ® -15 °C to +270 °C
Perfluoroelastomers combine the properties of elastomers with the almost universal chemical and temperature resistance of PTFE. Due to its high price, this material is only used in special cases.
FVMQ Fluorosilicone rubber FSE®, Silastic®, Sylon® -45 °C to +175 °C
Improved resistance to oils, fuels and solvents compared with MVQ, especially to aromatic and chlorinated hydrocarbons and alcohol. Suitable for demanding applications such as seals in automotive fuel systems, aerospace and the chemical industry.
HNBR Hydrogenated nitrile butadiene rubber Therban®, Zetpol® -15 °C to +150 °C
High mechanical strength, improved abrasion resistance and low compression set. Media resistance comparable to NBR with improved steam resistance.

Downloads

Product data sheet O-rings (PDF)
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