ISO 7685

Glass-reinforced thermosetting plastics (GRP) pipes — Determination of initial ring stiffness

This document specifies methods for determining the initial ring stiffness of glass-reinforced thermosetting plastics (GRP) pipes. Two methods are given (constant load and constant deflection), and within the specified deflection limits, each is equally valid and can be used for any diameter.

Tubes en plastiques thermodurcissables renforcés de verre (PRV) — Détermination de la rigidité annulaire initiale

General Information

• Status: Not Published
• ICS: 23.040.20 - Plastics pipes
• Technical Committee: ISO/TC 138/SC 6 - Reinforced plastics pipes and fittings for all applications
• Drafting Committee: ISO/TC 138/SC 6/WG 1 - Methods of test
• Current Stage: 6000 - International Standard under publication
• Start Date: 04-Dec-2025
• Completion Date: 13-Dec-2025

Relations

• Revises: ISO 7685:2019 - Glass-reinforced thermosetting plastics (GRP) pipes — Determination of initial ring stiffness
• Effective Date: 18-May-2024

Standards Content (Sample)

International
Standard
Third edition
Glass-reinforced thermosetting
plastics (GRP) pipes —
Determination of initial ring
stiffness
Tubes en plastiques thermodurcissables renforcés de verre
(PRV) — Détermination de la rigidité annulaire initiale
PROOF/ÉPREUVE
Reference number
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
PROOF/ÉPREUVE
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 3
5.1 Compressive-loading machine . .3
5.2 Load application surfaces .3
5.2.1 General arrangement.3
5.2.2 Plates .3
5.2.3 Beam bars .3
5.3 Dimension-measuring instruments.3
6 Test pieces . 4
6.1 Preparation .4
6.2 Number .4
6.3 Determination of dimensions .5
6.3.1 General .5
6.3.2 Length .5
6.3.3 Wall thickness .5
6.3.4 Mean diameter .5
7 Conditioning . 5
8 Procedure . 5
8.1 Test temperature .5
8.2 Positioning of the test piece .5
8.3 Application of load and measurement of deflection.6
8.3.1 General .6
8.3.2 Method A: Using constant load .6
8.3.3 Method B: Using constant deflection .6
9 Calculation . 7
10 Test report . 8
Bibliography . 9
PROOF/ÉPREUVE
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 138, Plastics pipes, fittings and valves for the
transport of fluids, Subcommittee SC 6, Reinforced plastics pipes and fittings for all applications.
This third edition cancels and replaces the second edition (ISO 7685:2019), which has been technically
revised.
The main changes are as follows:
— the formula for the definition of the mean diameter has been corrected;
— Notes have been added in 8.3.2 and 8.3.3.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
PROOF/ÉPREUVE
iv
International Standard ISO 7685:2025(en)
Glass-reinforced thermosetting plastics (GRP) pipes —
Determination of initial ring stiffness
1 Scope
This document specifies methods for determining the initial ring stiffness of glass-reinforced thermosetting
plastics (GRP) pipes. Two methods are given (constant load and constant deflection), and within the specified
deflection limits, each is equally valid and can be used for any diameter.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 3126, Plastics piping systems — Plastics components — Determination of dimensions
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
compressive load
F
load applied to a pipe to cause a diametric deflection
Note 1 to entry: Compressive load is expressed in newtons.
3.2
vertical deflection
y
vertical change in diameter of a pipe in a horizontal position in response to a vertical compressive load (3.1)
Note 1 to entry: Vertical deflection is expressed in metres.
3.3
relative vertical deflection
y/d
m
ratio of the vertical deflection, y (3.2) to the mean diameter, d (3.4) of the pipe
m
...

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ISO/TC 138/SC 6
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Date: 2025-10-2711-05
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Glass-reinforced thermosetting plastics (GRP) pipes —
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Determination of initial ring stiffness
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Tubes en plastiques thermodurcissables renforcés de verre (PRV) — Détermination de la rigidité annulaire
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ISO/DISPRF 7685:2025(en)
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Formatted: French (France)
E-mail: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO/DISPRF 7685:2025(en)
Contents
Foreword . iii
Scope . iii
Normative references . iii
Terms and definitions . iii
Principle. iii
Apparatus . iii
Compressive-loading machine . iii
Load application surfaces . iii
Dimension-measuring instruments . iii
Test pieces . iii
Preparation. iii
Number. iii
Determination of dimensions . iii
Conditioning . iii
Procedure . iii
Test temperature . iii
Positioning of the test piece . iii
Application of load and measurement of deflection . iii
Calculation . iii
Test report . iii
Bibliography . iii
Foreword . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 3
5.1 Compressive-loading machine . 3
5.2 Load application surfaces . 3
5.3 Dimension-measuring instruments . 3
6 Test pieces . 4
6.1 Preparation . 4
6.2 Number . 5
6.3 Determination of dimensions. 5
7 Conditioning . 5
8 Procedure . 5
8.1 Test temperature . 5
8.2 Positioning of the test piece . 6
8.3 Application of load and measurement of deflection . 6
9 Calculation . 8
10 Test report . 9
iii
ISO/DISPRF 7685:2025(en)
Bibliography . 10

iv
ISO/DISPRF 7685:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO documentsdocument should be noted. This document was drafted in accordance with the editorial rules
of the ISO/IEC Directives, Part 2 (see www.iso.org/directives 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
Field Code Changed
This document was prepared by Technical Committee ISO/TC 138, Plastics pipes, fittings and valves for the
transport of fluids, Subcommittee SC 6, Reinforced plastics pipes and fittings for all applications.
This third edition cancels and replaces the second edition (ISO 7685:2019), which has been technically
revised.
The main changes are as follows:
— correction of the formula for the definition of the mean diameter. has been corrected;
— addition of Notes have been added in 8.3.2 and 8.3.3.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.htmlwww.iso.org/members.html.
v
ISO/DISPRF 7685:2025(en)
Glass-reinforced thermosetting plastics (GRP) pipes — Determination
of initial ring stiffness
1 Scope
This document specifies methods for determining the initial ring stiffness of glass-reinforced thermosetting
plastics (GRP) pipes. Two methods are given (constant load and constant deflection), and within the specified
deflection limits, each is equally valid and can be used for any diameter.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 3126, Plastics piping systems — Plastics components — Determination of dimensions
3 Ter
...