ISO 9631:2018

Rubber seals - Joint rings for pipelines for hot-water supply up to 110 °C - Specification for the material

ISO 9631:2018 specifies material requirements for vulcanized rubber seals for hot drinking and non-drinking water supply (up to 110 °C). The different seal designations specified are defined according to seal type, seal application and the requirements for a particular seal (see Table 2). General requirements for finished joint seals are also given. Any additional requirements called for by the particular application are specified in the relevant product standards, taking into account that the performance of pipe joints is a function of the seal material properties, seal geometry and pipe joint design. This document is intended to be used where appropriate, in conjunction with product standards which specify performance requirements for joints. ISO 9631:2018 is applicable to joint seals for use with all pipeline materials, including metals, clay, fibre cement, concrete, reinforced concrete, plastics and glass-reinforced plastics. ISO 9631:2018 is applicable to elastomeric components of composite and non-composite seals. In the case of composite seals made from materials with hardness ranging from 76 IRHD to 95 IRHD, the requirements for elongation at break, compression set and stress relaxation apply only when the material participates in the sealing function or contributes to the long-term stability of the seal. The material requirements specified in this document are designed for long term performances and a potential lifetime of 50 years. The lifetime of a sealing depends not only on material performance but also on other parameters which are not defined in this document like the mounting design, the quality of assembly and the combination with operating conditions. Joint rings made from cellular rubber materials are not covered by this document.

Joints étanches en caoutchouc — Garnitures d'étanchéité destinées aux joints de canalisations pour la fourniture d'eau chaude jusqu'à 110 °C — Spécifications pour les matériaux

General Information

• Status: Published
• Publication Date: 05-Mar-2018
• ICS: 83.140.50 - Seals
• Technical Committee: ISO/TC 45/SC 4 - Products (other than hoses)
• Drafting Committee: ISO/TC 45/SC 4/WG 2 - Rubber seals
• Current Stage: 9093 - International Standard confirmed
• Start Date: 16-Jan-2024
• Completion Date: 13-Dec-2025

Relations

• Revises: ISO 9631:2003 - Rubber seals - Joint rings for pipelines for hot-water supply up to 110 degrees C - Specification for the material
• Effective Date: 21-Dec-2013

Overview

ISO 9631:2018 - Rubber seals - Joint rings for pipelines for hot‑water supply up to 110 °C - Specification for the material - defines material requirements for vulcanized rubber joint rings used in hot drinking and non‑drinking water systems up to 110 °C. The standard covers elastomeric material properties, classification by hardness and application class, general requirements for finished seals, testing methods and quality assurance. It is intended to be used together with product standards that set joint performance criteria.

Key Topics

• Scope and applicability: Applies to elastomeric components of seals for pipelines made of metals, concrete, plastics, glass‑reinforced plastics, etc. Cellular rubber joint rings are excluded.
• Classification:
  • Hardness classes (nominal IRHD): 50, 60, 70, 80, 90 (specified hardness ranges).
  • Service classes: T1, T2, T3 - increasing severity for hot‑water and district‑heating applications.
  • Seal types: Type A (EPM, EPDM, NBR, SBR or equivalents) and Type B (IIR, CIIR, BIIR butyl rubbers).
  • Drinking‑water designation adds the letter D.
• Material requirements and tests (examples): tensile strength, elongation at break, hardness tolerance, compression set (air and in hot water), accelerated ageing, stress relaxation, volume change in water, ozone resistance, tear strength. Test methods reference ISO standards (e.g., ISO 37, ISO 48, ISO 815‑1, ISO 188).
• Design life: Material requirements target long‑term performance with a potential design lifetime of 50 years, noting actual life also depends on joint design, assembly quality and operating conditions.
• Composite seals: For components with hardness 76–95 IRHD, some tests (elongation, compression set, stress relaxation) apply only if that component contributes to sealing or long‑term stability.

Applications

Who uses ISO 9631:2018 and why:

• Seal and gasket manufacturers - to specify compound formulations and verify testable properties for hot‑water joints.
• Piping system designers and OEMs - to select compatible joint rings for potable and non‑potable hot‑water pipelines.
• Water utilities, plumbing specifiers and contractors - to ensure compliance with long‑term sealing performance for hot‑water distribution and district heating secondary systems.
• Testing and certification labs - to apply standardized test methods and quality assurance procedures.

Practical benefits: ensures material compatibility with water quality, predictable aging behavior at elevated temperatures, and standardization across pipeline materials and installation contexts.

Related Standards (if applicable)

Relevant references cited by ISO 9631:2018 include:

• ISO 37 (tensile testing), ISO 48 (hardness), ISO 815‑1 (compression set), ISO 188 (accelerated ageing), ISO 1817 (effect of liquids), ISO 1431‑1 (ozone resistance), ISO 3384‑1 (stress relaxation), ISO 10508 (hot/cold water piping guidance).

Keywords: ISO 9631:2018, rubber seals, joint rings, hot‑water supply, elastomeric seals, pipeline seals, compression set, hardness IRHD, tensile strength, water quality compliance.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 9631
Third edition
2018-03
Rubber seals — Joint rings for
pipelines for hot-water supply up to
110 °C — Specification for the material
Joints étanches en caoutchouc — Garnitures d'étanchéité destinées
aux joints de canalisations pour la fourniture d'eau chaude jusqu'à
110 °C — Spécifications pour les matériaux
Reference number
©
ISO 2018
© ISO 2018
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
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Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Classification . 2
5 Requirements and test methods . 3
5.1 Requirements for material . . 3
5.1.1 General. 3
5.1.2 Effect on water quality . 7
5.2 Requirement for finished seals . 7
5.2.1 Dimensional tolerances. 7
5.2.2 Imperfections and defects . 7
5.2.3 Hardness . 7
5.2.4 Tensile strength and elongation at break . 7
5.2.5 Compression set in air . 7
5.2.6 Accelerated ageing in air . 8
5.2.7 Stress relaxation . 8
5.2.8 Volume change in water . 8
5.2.9 Ozone resistance . 8
5.2.10 Tear strength . 9
5.2.11 Compression set in water . 9
5.2.12 Splices of prevulcanized profile ends . 9
6 Testing . 9
6.1 Preparation of test pieces . 9
6.2 Test temperature .10
7 Quality assurance .10
8 Storage .10
9 Designation .10
10 Marking and labelling .10
Annex A (normative) Determination of splice strength .11
Annex B (normative) Determination of compression set in hot water at 110 °C for seals.12
Annex C (informative) Quality assurance .14
Annex D (informative) Guidance on storage of seals .15
Bibliography .16
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
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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 documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on 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 the following
URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 45, Rubber and rubber products,
Subcommittee SC 4, Products (other than hoses).
This third edition cancels and replaces the second edition (ISO 9631:2003), which has been technically
revised.
The main changes compared to the previous edition are as follows.
— Three different temperature classes (T1, T2 and T3) have been introduced. The requirements for
the lowest class (T1) are similar to the requirements in the second edition of this standard, while
classes T2 and T3 have been added in Table 2 to specify more severe requirements in order to deal
with more demanding applications.
— The test procedure for the hot water compression set (Annex B) has been revised to be more in line
with experiences over the last years.
iv © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 9631:2018(E)
Rubber seals — Joint rings for pipelines for hot-water
supply up to 110 °C — Specification for the material
WARNING — Persons using this document should be familiar with normal laboratory practice.
This standard does not purport to address all of the safety problems, if any, associated with its
use. It is the responsibility of the user to establish appropriate safety and health practices.
1 Scope
This document specifies material requirements for vulcanized rubber seals for hot drinking and non-
drinking water supply (up to 110 °C).
The different seal designations specified are defined according to seal type, seal application and the
requirements for a particular seal (see Table 2).
General requirements for finished joint seals are also given. Any additional requirements called for by
the particular application are specified in the relevant product standards, taking into account that the
performance of pipe joints is a function of the seal material properties, seal geometry and pipe joint
design. This document is intended to be used where appropriate, in conjunction with product standards
which specify performance requirements for joints.
This document is applicable to joint seals for use with all pipeline materials, including metals, clay, fibre
cement, concrete, reinforced concrete, plastics and glass-reinforced plastics.
It is applicable to elastomeric components of composite and non-composite seals. In the case of composite
seals made from materials with hardness ranging from 76 IRHD to 95 IRHD, the requirements for
elongation at break, compression set and stress relaxation apply only when the material participates in
the sealing function or contributes to the long-term stability of the seal.
The material requirements specified in this document are designed for long term performances and a
potential lifetime of 50 years. The lifetime of a sealing depends not only on material performance but
also on other parameters which are not defined in this document like the mounting design, the quality
of assembly and the combination with operating conditions. Joint rings made from cellular rubber
materials are not covered by this document.
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 34-2, Rubber, vulcanized or thermoplastic — Determination of tear strength — Part 2: Small (Delft)
test pieces
ISO 37, Rubber, vulcanized or thermoplastic — Determination of tensile stress-strain properties
ISO 48, Rubber, vulcanized or thermoplastic — Determination of hardness (hardness between 10 IRHD and
100 IRHD)
ISO 188:2011, Rubber, vulcanized or thermoplastic — Accelerated ageing and heat resistance tests
ISO 815-1, Rubber, vulcanized or thermoplastic — Determination of compression set — Part 1: At ambient
or elevated temperatures
ISO 1431-1, Rubber, vulcanized or thermoplastic — Resistance to ozone cracking — Part 1: Static and
dynamic strain testing
ISO 1629, Rubber and latices — Nomenclature
ISO 1817, Rubber, vulcanized or thermoplastic — Determination of the effect of liquids
ISO 3302-1, Rubber — Tolerances for products — Part 1: Dimensional tolerances
ISO 3384-1:2011, Rubber, vulcanized or thermoplastic — Determination of stress relaxation in
compression — Part 1: Testing at constant temperature
ISO 6914:2013, Rubber, vulcanized or thermoplastic — Determination of ageing characteristics by
measurement of stress relaxation in tension
ISO 9691:1992, Rubber — Recommendations for the workmanship of pipe joint rings — Description and
classification of imperfections
ISO 10508:2006, Plastics piping systems for hot and cold water installations — Guidance for classification
and design
ISO 15510, Stainless steels — Chemical composition
ISO 23529, Rubber — General procedures for preparing and conditioning test pieces for physical test methods
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at https:// www .electropedia .org/
— ISO Online browsing platform: available at https:// www .iso .org/ obp
4 Classification
4.1 Materials for pipe joint seals are classified based on their nominal hardness. A nominal hardness
shall be specified within the ranges in Table 1.
Table 1 — Hardness classification
Hardness class 50 60 70 80 90
Range of hardness, IRHD 46 to 55 56 to 65 66 to 75 76 to 85 86 to 95
4.2 On top of that, three classes for the use of the materials are specified in Table 2.
Table 2 — Classes and designation of elastomeric joint seals by type, application and
requirements
Class Application Requirements Subclause
Tables 3 and 4
Hot water systems where the temperature is high (up to 85 °C)
T1 5.1.2
during tapping and low (ambient) when no water is used.
(Effect on water quality)
Tables 5 and 6
Hot water circulation systems based on the classification class
T2 5.1.2
2 in ISO 10508:2006
(Effect on water quality)
Tables 7 and 8
District heating, secondary systems with hot water circulation
T3 5.1.2
a
between 75 °C and 95 °C
(Effect on water quality)
a
T3 is based on EN 253.
2 © ISO 2018 – All rights reserved

A material of one type qualified for one class is automatically qualified for the inferior class.
4.3 Furthermore a difference is made for two types of sealing principle:
— Type A: Seals based on EPM, EPDM, NBR, SBR or equivalent polymers as typical materials;
— Type B: Seals based on IIR, CIIR or BIIR (butylic rubbers) or equivalent as typical materials.
4.4 If products are intended for drinking water, the letter D is added to the designation.
5 Requirements and test methods
5.1 Requirements for material
5.1.1 General
Requirements are summarized in Tables 3, 4, 5, 6, 7 and 8 for each class. The material shall be free of
any substances which could have a deleterious effect on the water transported, or on the life of the
sealing ring, or on the pipe or fitting. Elastomeric components of composite seals not exposed to the
contents of the pipeline are not required to meet the requirements of 5.1.2.
Table 3 — Physical-property requirements for type A materials used in class T1 applications
Property Unit Test Sub- Requirements for hardness classes
method clause 50 60 70 80 90
Permissible tolerance on nomi-
IRHD ISO 48 5.2.3 ±5 ±5 ±5 ±5 ±5
nal hardness
Tensile strength, min. MPa ISO 37 5.2.4 9 9 9 9 9
Elongation at break, min. % ISO 37 5.2.4 250 200 150 100 100
Compression set, max.
% ISO 815-1 5.2.5.2
72 h at 23 °C 15 15 15 15 15
% ISO 815-1 5.2.5.2
24 h at 125 °C 20 20 20 20 20
Ageing, 7 days at 125 °C ISO 188 5.2.6
IRHD
Hardness change, max. ISO 48 +8/–5 +8/–5 +8/–5 +8/–5 +8/–5
%
Tensile strength change, max. ISO 37 –20 –20 –20 –20 –20
%
Elongation change, max. ISO 37 +10/–30 +10/–30 +10/–30 +10/–40 +10/–40
Stress relaxation, max % ISO 3384-1 5.2.7
7 days at 23 °C or 15 15 15 18 18
7 days at 125 °C ISO 6914 30 30 30 30 30
Volume change in water, max. % ISO 1817 5.2.8
+8/–1 +8/–1 +8/–1 +8/–1 +8/–1
7 days at 95 °C
Ozone resistance — ISO 1431-1 5.2.9 No cracking when viewed without magnification
Tear strength, min. N ISO 34-2 5.2.10 20 20 20 20 20
Table 4 — Physical-property requirements for type B materials used in class T1 applications
Property Unit Test method Sub- Requirements for hardness classes
clause 50 60 70 80
Permissible tolerance on nomi-
IRHD ISO 48 5.2.3 ±5 ±5 ±5 ±5
nal hardness
Tensile strength, min. MPa ISO 37 5.2.4 9 9 9 9
Elongation at break, min. % ISO 37 5.2.4 250 200 150 100
Compression set, max.
% ISO 815-1 5.2.5.2
72 h at 23 °C 15 15 15 15
% ISO 815-1 5.2.5.2
24 h at 125 °C 20 20 20 20
Ageing, 7 days at 125 °C 5.2.6
ISO 188
IRHD
Hardness change, max.
ISO 48 +8/–5 +8/–5 +8/–5 +8/–5
%
Tensile strength change,
ISO 37 –20 –20 –20 –20
max.
%
ISO 37 +10/–30 +10/–30 +10/–30 +10/–40
Elongation change, max.
% ISO 3384-1 5.2.7
Stress relaxation, max
or 15 15 15 18
7 days at 23 °C
ISO 6914
No cracking when viewed without magni-
Ozone resistance — ISO 1431-1 5.2.9
fication
Compression set in water for
% Annex B 5.2.11 30 30 30 30
1 680 h at 110 °C, max.
Table 5 — Physical-property requirements for type A materials used in class T2 applications
Property Unit Test Sub- Requirements for hardness classes
method clause 60 70 80
Permissible tolerance on nominal
IRHD ISO 48 5.2.3 ±5 ±5 ±5
hardness
Tensile strength, min. MPa ISO 37 5.2.4 9 9 9
Elongation at break, min. % ISO 37 5.2.4 200 150 100
Compression set, max.
% ISO 815-1 5.2.5.2
72 h at 23 °C 15 15 15
% ISO 815-1 5.2.5.2
24 h at 125 °C 20 20 20
Ageing, 7 days at 125 °C ISO 188 5.2.6
IRHD
Hardness change ISO 48 +8/–5 +8/–5 +8/–5
%
Tensile strength change, max. ISO 37 –20 –20 –20
%
Elongation change ISO 37 +10/–30 +10/–30 +10/–40
Stress relaxation, max % ISO 3384-1 5.2.7
7 days at 23 °C or 15 15 18
7 days at 125 °C ISO 6914 30 30 30
Stress relaxation, max. % ISO 6914 5.2.7
55 55 55
21 days at 140 °C
Volume change in water % ISO 1817 5.2.8
+8/–1 +8/–1 +8/–1
7 days at 95 °C
4 © ISO 2018 – All rights reserved

Table 5 (continued)
Property Unit Test Sub- Requirements for hardness cla
...