ISO 9691:1992

Rubber - Recommendations for the workmanship of pipe joint rings - Description and classification of imperfections

Classifies imperfections in surface and internal imperfections and specifies maximum acceptable limits.

Caoutchouc — Recommandations concernant l'exécution des garnitures d'étanchéité pour joints de canalisation — Description et classification des imperfections

General Information

• Status: Published
• Publication Date: 11-Nov-1992
• ICS: 23.040.80 - Seals for pipe and hose assemblies
• 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

Overview

ISO 9691:1992 - Rubber - Recommendations for the workmanship of pipe joint rings - Description and classification of imperfections provides manufacturers and users of rubber pipe joint rings with a clear vocabulary and criteria to describe, inspect and classify workmanship defects. The standard targets both surface imperfections and internal imperfections, and gives guidance on inspection methods and acceptable limits. It is a recommendations document (not a prescriptive specification): final acceptance of defects is to be agreed between the interested parties.

Key topics

• Scope and purpose
  • Describes typical manufacturing imperfections in rubber pipe joint rings and gives criteria for assessing workmanship quality.
  • Intended to support compliance with requirements in related product standards (e.g., requirements that rings “shall be free from porosity and surface defects that affect function”).
• Classification of imperfections
  • Surface imperfections grouped into three types:
    • Not involving excess/shortage (e.g., bloom, surface inclusions, cuts, crazing)
    • Excess material (e.g., flash, offset, mismatch)
    • Shortage of material (e.g., backrind, parting-line indentation, excessive trimming, flow marks, surface depressions)
  • Internal imperfections such as blisters/porosity and foreign material are described and their functional impact noted.
• Inspection and assessment
  • Surface inspection recommended with a x2 magnifying lens and slight stretching/bending to reveal hidden defects; avoid excessive stretching.
  • Internal defects assessed by comparing compression stress–strain (ISO 7743) or density (ISO 2781) of samples from a suspect part against a good reference.
• Acceptable limits
  • Sealing zones must be free of all surface imperfections except bloom.
  • Non-sealing zones are classified into major and minor imperfections with numeric thresholds (the standard provides a table of dimensional limits for features such as flash height/thickness, offset percentage, cut depth/length, backrind depth, flow-mark dimensions).

Applications and who uses it

• Useful for manufacturers of rubber joint rings to design moulds, control production and set trimming practices.
• Employed by quality inspectors, purchasers, and contracting engineers to interpret workmanship requirements and to decide acceptance criteria during incoming inspection or contract negotiation.
• Relevant to industries that use pipeline seals for water, gas, sewage and petroleum distribution.

Related standards

• ISO 7743 - compression stress–strain testing (referenced for internal assessment)
• ISO 2781 - density determination (referenced for internal assessment)
• ISO 4633, ISO 6447, ISO 6448 - related material and product standards for rubber joint rings

Keywords: ISO 9691:1992, rubber pipe joint rings, workmanship, imperfections, surface defects, internal defects, flash, offset, backrind, porosity, inspection, quality control.

Standards Content (Sample)

INTERNATIONAL
STANDARD
First edition
1992-11-15
-
~~.~-~-~--~~~~,~___- .---- ---
Rubber - Recommendations for the
workmanship of pipe joint rings - Description
and classification of imperfections
Recommandations concernant l’execution des garnitures
Caoutct?ouc -
- Description et classifkation
d’6iancMft5 pour joint de canalisafion
des imper-fections
Reference number
ISO 9691: 1992( E)
Foreward
ISO (the International Organization for Standardization) is a woridwide
federation of national Standards bodies (ISO member bodies). The work
of preparing International Standards is normally carried out through ISO
technical cornmittees. Esch 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, govern-
mental and non-governmental, in liaison with ISO, also take part in the
work. ISO collaborates closely with the International Etectrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an Inter-
national Standard requires approval by at least 75 % of the member
bodies castinq a vote.
L
International Standard ISO 9691 was prepared by Technical Committee
ISO/TC 45, Rubber and rubber producfs, Sub-Committee SC 4, Miscel-
laneous products.
Annex A of this International Standard is for information only.
0 ISO 1992
All rights reserved. No part of this publication may be reproduced or utilized in any fort-n
or by any means, electronie or mechanical, including photocopying and microfilm, withorrt
permission in writing from the publisher.
International Organization for Standardization
Case Postale 36 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
ii
Introduction
International Standards such as ISO 4633P1, ISO 6447121 and ISO 6448M
(see bibliography) for rubber joint rings for pipelines include some gen-
eral requirements for the finished rings, pat-ticularly for workmanship,
in Statements such as: “The rings shall be free from porosity and shall
not have surface defects or irregularities which could affect their func-
tions”.
In Order to assist manufacturers wishing to comply with such require-
ments, this International Standard describes manufacturing imperfec-
tions which could arise during the production of pipe joint rings, and lists
criteria by which the quality of workrnanship tan be assessed. lt should
be stressed, however, that this International Standard is not a specifi-
cation. Whether an imperfection is to be considered as a defect will ul-
timately have to be agreed upon between the interested Parties (see
clause 4).
. . .
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- Recommendations for the workmanship of pipe
Rubber
- Description and classification of imperfections
joint rings
3.1.1 Imperfections not involving excess or
1 Scope
shortage of material
This International Standard describes and classifies
imperfections in rubber joint rings for pipelines.
3.1.1.1 Bloom: A liquid or solid material which has
migrated to the surface of a rubber.
2 Normative references
3.1.1.2 Surface inclusion (foreign material): Any
The following Standards contain provisions which,
extraneous matter embedded in the surface.
through reference in this text, constitute provisions
of this International Standard. At the time of publi-
cation, the editions indicated were valid. All stan- 3.1.1.3 Cut: A fine incision similar to that made by
dards are subject to revision, and Parties to a scalpel. The tut is not open. lt is usually necessary
agreernents based on this International Standard to stretch the rubber for the edges of the tut to be-
are encouraged to investigate the possibility of ap- come clearly visible.
plying the most recent editions of the Standards in-
dicated below. Members of IEC and ISO maintain
3.1 .1.4 Cracking: A network of fine Cracks or
registers of currently valid International Standards.
crazing which is not visible unless the rubber is
folded. lt may be caused, for example, by ageing or
ISO 2781: 1988, Rubber, vulcanized - Determination
incorrect storage.
of densify.
ISO 7743~1989, Rubber, vulcanized or thermoplastic
-- Determination of compression stress-strain prop-
3.1.2 Excess material
erties.
3.1.2.1 Flash (see figure 1): Excess material which
3 Classification of imperfections
escapes from the moulding cavity during moulding
of a moulded ring, or is produced at the weld line
3.1 Surface imperfections
of an extruded welded ring, and solidifies to form a
film-Iike appendage. It is caused by mould separ-
There are three types of surface imperfection:
ation and is present owing to inadequate trimming.
a) imperfections not involving excess or shortage
of material (see 3.1.1);
3.1.2.2 Qffset: Joint ring halves that are off-register
or mismatched.
b) excess material (see 3.1.2);
3.1.2.2.1 Off-register (see figure 2): Misalignment of
c) shortage of material (sec 3.1.3).
joint ring halves caused by lateral shift of one mould
cavity plate or one end of the extrusion relative to
NOTE 1 Some surface imperfections, e.g. offset and
the other.
shortage of materiai, tan appear in combination.
l------------
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- Flash hefght
I -Flash thlckness
l
t
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,
l
t
a) Moulded rlnq
b) Extruded welded rlnq
’
Figure 1 - Flash
e
Externat
a) Moulded rlq
ter
b) Extruded welded rk~~
Figure 2 - Off-register
3.1.2.2.2 Mismatch (see figure 3): Abrupt chanqe in and has a U- or W-shaped Cross-section, with the
Cross-section of a joint ring, caused vvhen- the flash frequently being ragged or torn.
Cross-sectionai dimensions of one mould cavity
3.1.3.2 ßarting-line indentation [see figure 4 b)]: A
plate are not equal to those of the other plate or, in
the case of extruded welded rings, the cross- shallow saucer-like recess, sometimes triangular in
sectional dimensions of the two ends are unequal. shape, located along the parting line where the two
ring ends have been welded together. lt is caused
by deformation of the mould edge at the parting line.
3.1.3
S hortage of material
3.1.3.3 Excessive trimming (see figu re 5): A flat-
3.1.3.1 Backrind [see figure4 a)]: A longitudinal
tened and often roughened area around the inside
imperfection in which the rubber adjacent to the
and/or outside of the joint ring. lt is caused by trim-
flash line shrinks below the ievel of the moulding
ming off too much flash.
a) Moulded rlnq
e
b) Extruded welded rlng
Figur
...