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  • Premiu

    m qual

    ity

    since

    1867

    When it matters ...

    O-Ring BASICS Everything about O-Ring seals

  • 2

    For the benefit of our clients

    Europe's largest O-Ring warehouse

    C. Otto Gehrckens abbreviated COG has offered its clients uncompromising premium quality for over 140 years. The combination of tradition and innovation at COG is the key to our success. This is demonstrated daily in our customer relations. Our clients are among the best in their respective industries. And they expect the best from us.

    Over 190 employees are committed at COG to our clients' success, ranging from engineers in the application technology department to our colleagues in Europe's largest O-Ring warehouse with their rapid response capabilities. COG is an independent manufacturer based in Pinneberg near Hamburg and is managed by the fifth generation of the founding family. We are a leading supplier of precision O-Rings and elastomer seals thanks to our comprehensive stock, flexible production facilities and commitment to customer service.

    Our clients define the aims of everything we do. New ideas and products are developed quickly and in a market and goal-oriented manner in close cooperation with the application technology and sales department. The result is often a major market benefit to our clients. Please refer to www.cog.de or contact us directly for more information. Let's discuss your aims.

    For furtherinformation please

    have a look at

    www.COG.de or contact us

    directly.

  • 3

    Founded in 1867 in Pinneberg near Hamburg

    Independent family company with more than 190 employees

    Optimised delivery service from our new logistics centre

    Quality management per DIN EN ISO 9001:2008

    Environmental management per DIN EN ISO 14001:2009

    Europe's largest O-Ring warehouse (over 45,000 items in stock)

    Tools for over 15,000 different O-Ring sizes available

    Own tool manufacture

    Close cooperation with leading raw material manufacturers

    In-house mixing and mixture development

    Certifications and approvals granted for many materials (BfR, KTW, DVGW, NSF/ANSI)

    COG at a glance

    Inhalt

    Content page General (description, materials) .................................... 4Rubber nomenclature .................................................... 6Rubber and its trade names .......................................... 7O-Ring function ............................................................. 8Hardness ....................................................................... 9Pressure loading (O-Ring behaviour under pressure) .. 10Thermal characteristics ................................................. 11Media resistance .......................................................... 12Groove geometry for installation spaces(groove depth and width) .............................................. 13Definition of installation types ....................................... 14Piston seal ..................................................................... 15Rod seal ......................................................................... 18Flange seal ................................................................... 20

    Trapezoidal groove ........................................................ 23Triangular groove ........................................................... 23 O-Ring installation types ............................................... 24Surface roughness ........................................................ 25Installation spaces for PTFE O-Rings ........................... 26O-Ring storage .............................................................. 27Surface treatment .......................................................... 28Chemical resistance list ................................................ 29Certifications/approvals ................................................ 42DIN 3771 ........................................................................ 44ISO 3601:2008 standard ................................................ 46Deviations between DIN 3771 and ISO 3601 ................ 49Index of key words ........................................................ 50

  • O-Ring sizing

    d1 d2

    Compression process

    Slug

    Open mould Closed mould

    Injection process

    Heating system

    Closed mould Injection process

    Worm

    4

    General

    An O-Ring seal is a means of preventing unwanted leakage or loss of fluid or gas (i. e. media generally).

    The O-Ring is the most popular form of seal as it is simple to install and needs little installation space. Given correct grooving and material choice, the seal can be used for a very long time within the rubber's temperature limits both as a fixed and as a moving part.

    DescriptionAn O-Ring is a closed circle usually made of flexible rubber (elastomer). The dimensions are defined by the inside diameter d1 and the cross-section d2.

    O-Rings are gaplessly and seamlessly made of various types of natural rubber in hot injection or press moulds by vulcanisation (cross-linking).

    Manufacturing processesGenerally there are two different manufacturing processes for the production of elastomer O-Rings possible.

    Compression process (Compression moulding = CM process)

    Injection moulding (Injection moulding = IM process)

    In CM the slug is manually inserted in the tool (mould) before the two mould halves consisting of an upper and a lower part are closed. As this process is very time-consuming, it is primarily suitable for manufacturing smaller quantities and larger dimensions.

    In injection moulding the slug is automatically injected into the tool, which contains several O-Ring cavities. This process is particularly suit-able for large quantities and small dimensions.

    O-Ring description

    Compression process

    Injection moulding

  • Picture of rubber (caoutchuc) macromolecules

    Picture of rubber macromolecules (cross-linked)

    5

    Elastomers / rubberElastomers are polymers whose macro-molecules have been linked with one another to form a network with cross-connections. As a result they show the typical rubbery and elastic properties. The raw, non-networked product is called rubber (caoutchouc), and is either obtained from plants that yield the substance or produced synthetically.

    Vulcanisation results in the networking of the macromolecules that is to say, the formation of chemical cross-links between the polymer chains. This has the effect that following the termination of an enforced change of form, elastomers will return to their original shape.

    MaterialsTechnical rubber materials are structured on the basis of a formula. In terms of chemical resistance, the polymer is the weakest link of the different constituent components as compared with the media to be sealed off.

    The choice of the right sealing material is often hence restricted to basic polymer(s). In practice, other influences, such as the type of cross-linking, the quantity of softener(s) used and the type of filler employed may be of significance due to the recipe used. Polymer tolerability alone is hence no guarantee of a reliable seal but is a major precondition.

    iNOTE:The components of a formula are generally given in phr (parts per hundred rubber).This is the number of parts of filler material in relation to 100 parts of rubber (polymer).

    Elastomers

    Sealing material

    Ingredient Quantity in phrContingent

    in %

    Rubber (polymer) 100.0 39.0

    Filler materials 90.0 35.1

    Softener 50.0 19.4

    Processing aids 3.0 1.2

    Ageing prevention media

    4.0 1.5

    Cross-linking media (sulphur)

    2.0 0.8

    Activator (organic product)

    1.7 0.7

    Dispersant (stearic acid)

    2.0 0.8

    Cross-linking activator (zinc oxide)

    4.0 1.5

    Total 256.7 100.0

    Constituent components of a sample formula for NBR rubber

  • 6

    The synthesis rubbers are classified per IS0 1629 or ASTM D 1418.

    Rubbers in solid form are classified in the following groups according to the chemical composition of their polymer chain:

    DIN ISO 1629

    ASTM D 1418

    Rubber nomenclature

    Overview of the major rubber types with brief designation and COG no.

    Group Chemical name DIN ISO 1629 ASTM D 1418 COG no.

    M Polyacrylate rubber ACM ACM AC

    M Chlorpolyethylene rubber CM CM --

    M Ethylene acrylate rubber AEM AEM --

    M Chlorsulphurated-polyethylene rubber CSM CSM --

    M Ethylene-propylene rubber EPM EPM EP

    M Ethylene-propylene-(dien) rubber EPDM EPDM AP ...

    M Fluoride rubber

    FKM FKMLT Vi

    FEPM FEPMAFVi

    M Perfluor rubber FFKM FFKM Perlast

    O Epichlorhydrine rubber CO CO --

    O Epichlorhydrine-copolymer rubber ECO ECO --

    O Propylenoxide-copolymer rubber GPO GPO --

    R Butadine rubber BR BR --

    R Chloroprene rubber CR CR NE

    R Isobutene-isopropene rubber IIR IIR BT ...

    R Isopropene rubber IR IR --

    R Acrylnitrile-butadine rubber NBR NBR P ...

    R Hydrated acrylnitrile-butadiene rubber HNBR HNBR HNBR ...

    R Natural-rubber NR NR K ...

    R Styrol-butadine rubber SBR SBR --

    Q Fluor-vinyl-methyl-silicone rubber FVMQ FVMQ Si FL

    Q Phenyl-methyl-silicone rubber PMQ PMQ --

    Q Phenyl-vinyl-methyl-silicone rubber PVMQ PVMQ --

    Q Vinyl-methyl rubber VMQ VMQ Si

    Q Methyl-silicone rubber MQ MQ --

    U Polyesterurethane rubber AU AU PU

    U Polyetherurethane rubber EU EU EU ...

  • 7

    The table below provides an overview of some selected rubbers from which elastomer sealing materials a