Cooperating organizations

The Mechanical Engineering Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following:

Associated Offices Technical Committee

Association of Consulting Engineers

Association of Hydraulic Equipment Manufacturers*

Association of Mining Electrical and Mechanical Engineers

British Compressed Air Society*

British Electrical and Allied Manufacturers' Association (BEAMA)

British Gas Corporation

British Gear Manufacturers’ Association

British Internal Combustion Engine

Manufacturers' Association

British Pump Manufacturers’ Association

British Steel Corporation

British Steel Industry*

Chartered Institution of Building Services

Crown Agents for Oversea Governments and Administrations

Department of Industry, Mechanical Engineering

Department of Industry, National Engineering Laboratory

Department of the Environment (PSA)

Department of Trade (Marine Division)

Department of Transport

Electricity Supply Industry in England and Wales

Energy Industries Council

Engineering Equipment Users' Association*

Federation of Manufacturers of Construction Equipment and Cranes

Health and Safety Executive

Institution of Gas Engineers

Institution of Mechanical Engineers

Institution of Plant Engineers

Institution of Production Engineers

Lloyd's Register of Shipping

London Transport Executive

Machine Tool Industry Research Association

Ministry of Defence*

National Coal Board*

Oil Companies Materials Association

Process Plant Association

Society of Motor Manufacturers and Traders Limited*

Telecommunication Engineering and Manufacturing Association (TEMA)

Water-tube Boilermakers' Association

The organizations marked with an asterisk in the above list, together with thefollowing, were directly represented on the Technical Committee entrusted with the preparation of this British Standard:

British Hydromechanics Research Association

British Rubber Manufacturers’ Association

Hydraulic Press Manufacturers’ Association

Society of British Aerospace Companies Limited

This British Standard, having been prepared under the direction of the Mechanical Engineering Standards Committee, was published under the authority of the board of BSI and comes into effect on 30 April 1982

First published November 1969

First revision July 1974

Second revision April 1982

The following BSI references relate to the work on this standard:

Committee reference MEE/109 Drafts for comment 81/73664 DC, 14/30295993 DC

Foreword

This British Standard is published by BSI Standards Limited, under licence from the British Standards Institution, and came into effect on 30 April 1982.

This British Standard has been prepared under the direction of the Mechanical Engineering Standards Committee. It revises and supersedes the 1974 edition which is now withdrawn.

BS 4518:1982+A2:2014 supersedes BS 4518:1982, incorporating Amendment No. 1:1984, which is withdrawn.

Text introduced or altered by Amendment No. 2 is indicated in the text by tags . Minor editorial changes are not tagged. Previous amendments are not indicated.

Amendment No. 2 introduces the following principal changes:

Standards references have been updated.
Some additional preferred sizes in accordance with BS ISO 3320 have been cross-referred to in Table 1, Table 7, Table 8 and Table B.1.

The first edition of the standard, published in 1969, introduced a new range of metric sizes for elastomeric toroidal sealing rings which were based upon European practices. In order to permit the introduction of additional sizes, a reference numbering system, based upon the “O”-ring internal diameter and section diameter, was adopted.

The first revision of the standard, published in 1974, introduced a further 4.1 mm diameter of “O”-ring section. The opportunity was also taken to improve the presentation of the information provided.

In this second revision, additional sizes have been introduced to cater for the preferred range of cylinder bores and piston rod diameters specified in BS ISO 3320. Groove dimensions for pneumatic applications have also been added. In addition, two charts have been included in Appendix A to aid selection of appropriate seals for given applications.

Previous editions of this standard contained information on the limits for surface imperfections of “O”-rings. These are now covered by BS ISO 3601‑3.

Because of the lack of demand for the 4.1 mm section rings which were introduced in the 1974 edition, requirements for these rings are not included in this revision. However, details of the rings are given in Appendix B for information if required for replacement purposes.

It is stressed that the dimensions specified in this standard, although providing the necessary basis for standardization in the manufacture and application of “O”-rings, should not be regarded as providing all the information required for design purposes. Attention is drawn to the desirability of consultation between users and manufacturers of “O”-rings, when a particular application of this type of seal is being considered.

It is recognized that inch series “O”-rings will continue to be required. Requirements for such “O”-rings are specified in BS ISO 3601‑1 and BS ISO 3601‑2.

This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

Summary of pages

This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 28, an inside back cover and a back cover.

This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.

1 Scope

This British Standard specifies the dimensions of elastomeric “O”-rings which are toroidal in shape and which are used for sealing components against ingress or egress of fluids under dynamic and static conditions.

The standard also specifies the shape and dimensions of five types of associated housing grooves for the rings when used at pressures not normally exceeding 100 bar ¹⁾.

NOTE At pressures exceeding 100 bar, or when the diametral clearances of the grooves are in excess of those specified in this standard, it is recommended that these “O”-rings should be used in conjunction with anti-extrusion back-up rings. Spiral anti-extrusion back-up rings and their housings, the dimensions of which are specified in BS 5106, are suitable for pressures up to approximately 200 bar.

Two charts are provided in Appendix A to aid the selection of “O”-rings.

2 References

3 “O”-rings

3.1

3.2

3.3

3.4

4 Housing grooves

4.1

4.2

4.3

4.4

4.5

BS 4518:1982+A2:2014

Specification for metric dimensions of toroidal sealing rings ('O'-rings) and their housings

Current

Published:

30 Apr 1982