Foreword

Publishing information

This British Standard is published by BSI Standards Limited, under licence from The British Standards Institution, and came into effect on 30 April 2024. It was prepared by Technical Committee MCE/11, Fluid seals and their housings. A list of organizations represented on this committee can be obtained on request to the committee manager.

Supersession

This British Standard supersedes BS 5106:1988, which is withdrawn.

Relationship with other publications

This British Standard was developed from, and is complementary to, BS 4518.

Information about this document

This is a full revision of the document, and introduces the following principal changes:

• the preferred shaft (rod) and cylinder diameters in accordance with BS ISO 3320 are indicated; and
• references have been updated.

Annex A gives guidance on the assembly of spiral back-up rings into their housings.

Due to the lack of demand for the 4.1 mm section rings introduced in BS 4518:1974, requirements for the compatible back-up rings are not included in this revision. However, details of the rings are given in Annex B and for information if required for replacement purposes. This parallels similar changes introduced into BS 4518:1982.

The efficient use of “O”-rings depends upon the ability of the elastomeric “O” ring to resist extrusion through the working clearances between mating parts. Under certain circumstances it is necessary to increase the resistance to extrusion by the use of back-up rings. This British Standard specifies requirements for a range of spiral back-up rings that are compatible with “O” rings manufactured in accordance with BS 4518.

The width and radial depth of the grooves specified here are such that the spiral back-up rings, by virtue of their coiling action, may be fitted in assemblies in which the internal or external diameter is a rounded metric dimension.

It is stressed that the dimensions specified in this British Standard, although providing the necessary basis for standardization in the manufacture and application of spiral back-up 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 and spiral back up rings, when a particular application is being considered.

This publication can be withdrawn, revised, partially superseded or superseded. Information regarding the status of this publication can be found in the Standards Catalogue on the BSI website at knowledge.bsigroup.com, or by contacting the Customer Services team.

Where websites and webpages have been cited, they are provided for ease of reference and are correct at the time of publication. The location of a webpage or website, or its contents, cannot be guaranteed.

Presentational conventions

The provisions of this document are presented in roman (i.e. upright) type. Its requirements are expressed in sentences in which the principal auxiliary verb is “shall”.

Commentary, explanation and general informative material is presented in smaller italic type, and does not constitute a normative element.

Where words have alternative spellings, the preferred spelling of the Shorter Oxford English Dictionary is used (e.g. “organization” rather than “organisation”).

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

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

BS 5106:2024

Dimensions of spiral anti-extrusion back-up rings and their housings. Specification

Current

Published:

29 Apr 2024