SIST EN ISO 4126-2:2019

SLOVENSKI STANDARD
SIST EN ISO 4126-2:2019
01-maj-2019
1DGRPHãþD
SIST EN ISO 4126-2:2003
SIST EN ISO 4126-2:2003/AC:2004
SIST EN ISO 4126-2:2003/AC:2007
1DSUDYH]DYDURYDQMHSUHGYLVRNLPWODNRPGHO1DSUDYH]UD]SRþQLPL
PHPEUDQDPL,62
Safety devices for protection against excessive pressure - Part 2: Bursting disc safety
devices (ISO 4126-2:2018)
Sicherheitseinrichtungen gegen unzulässigen Überdruck - Teil 2:
Berstscheibeneinrichtungen (ISO 4126-2:2018)
Dispositifs de sécurité pour protection contre les pressions excessives - Partie 2:
Dispositifs de sûreté à disque de rupture (ISO 4126-2:2018)
Ta slovenski standard je istoveten z: EN ISO 4126-2:2019
ICS:
13.240 Varstvo pred previsokim Protection against excessive
tlakom pressure
SIST EN ISO 4126-2:2019 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 4126-2:2019

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SIST EN ISO 4126-2:2019


EN ISO 4126-2
EUROPEAN STANDARD

NORME EUROPÉENNE

March 2019
EUROPÄISCHE NORM
ICS 13.240 Supersedes EN ISO 4126-2:2003
English Version

Safety devices for protection against excessive pressure -
Part 2: Bursting disc safety devices (ISO 4126-2:2018)
Dispositifs de sécurité pour protection contre les Sicherheitseinrichtungen gegen unzulässigen
pressions excessives - Partie 2: Dispositifs de sûreté à Überdruck - Teil 2: Berstscheibeneinrichtungen (ISO
disque de rupture (ISO 4126-2:2018) 4126-2:2018)
This European Standard was approved by CEN on 3 December 2018.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.





EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 4126-2:2019 E
worldwide for CEN national Members.

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SIST EN ISO 4126-2:2019
EN ISO 4126-2:2019 (E)
Contents Page
European foreword . 3
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive 2014/68/EU (PED) aimed to be covered . 4

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SIST EN ISO 4126-2:2019
EN ISO 4126-2:2019 (E)
European foreword
This document (EN ISO 4126-2:2019) has been prepared by Technical Committee ISO/TC 185 "Safety
devices for protection against excessive pressure" in collaboration with Technical Committee CEN/TC
69 “Industrial valves” the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by September 2019, and conflicting national standards
shall be withdrawn at the latest by September 2019.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 4126-2:2003.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association, and supports essential requirements of EU Directive(s).
For the relationship with EU Directive(s) see informative Annex ZA, which is an integral part of this
document.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 4126-2:2018 has been approved by CEN as EN ISO 4126-2:2019 without any
modification.

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SIST EN ISO 4126-2:2019
EN ISO 4126-2:2019 (E)
Annex ZA
(informative)

Relationship between this European Standard and the Essential
Requirements of EU Directive 2014/68/EU (PED) aimed to be covered
This European Standard has been prepared under a Commission’s standardization request to provide
one voluntary means of conforming to Essential Requirements of New Approach Directive 2014/68/EU,
Pressure Equipment Directive (PED).
Once this document is cited in the Official Journal of the European Union under that Directive,
compliance with the normative clauses of this document given in Table ZA.1 confers, within the limits of
the scope of this document, a presumption of conformity with the corresponding essential
requirements of that Directive and associated EFTA regulations.
Table ZA.1 — Correspondence between this European Standard and Annex I of the Directive
2014/68/EU
Essential Requirements of Clause(s)/sub-clause(s) Remarks/Notes
Directive 2014/68/EU of this EN
Clause 1.3 and 3.4 11 Protection against misuse and
instructions for the user
Clause 2.1 5, 6.1.2, 6.2, 7 to 10, 12 General design
Clause 2.2.2 6.1.1 Design for adequate strength
The experimental method limited to
PN x DN less than 3 000
Clause 2.3 6.1.2 Safe operation
Clause 2.6 4.3 Corrosion
Clause 3.1.2, paragraphs 2 11.3
Permanent joining
and 3
Clause 3.3 17 Marking and labelling
WARNING 1 — Presumption of conformity stays valid only as long as a reference to this European
Standard is maintained in the list published in the Official Journal of the European Union. Users of this
document should consult frequently the latest list published in the Official Journal of the European
Union.
WARNING 2 — Other Union legislation may be applicable to the product(s) falling within the scope of
this document.
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SIST EN ISO 4126-2:2019
INTERNATIONAL ISO
STANDARD 4126-2
Second edition
2018-12
Safety devices for protection against
excessive pressure —
Part 2:
Bursting disc safety devices
Dispositifs de sécurité pour protection contre les pressions
excessives —
Partie 2: Dispositifs de sûreté à disque de rupture
Reference number
ISO 4126-2:2018(E)
©
ISO 2018

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SIST EN ISO 4126-2:2019
ISO 4126-2:2018(E)

COPYRIGHT PROTECTED DOCUMENT
© 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

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SIST EN ISO 4126-2:2019
ISO 4126-2:2018(E)

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Materials . 4
4.1 Selection of materials . 4
4.2 Material specifications . 4
4.3 Protection from corrosion . 5
5 Types of bursting discs. 5
5.1 Conventional domed bursting discs (Forward acting) . 5
5.2 Reverse domed bursting discs (Reverse acting) . 6
5.3 Flat bursting discs . 6
5.4 Other types and designs . 8
6 Bursting disc holders . 8
6.1 Design . 8
6.1.1 Pressure-containing capability . 8
6.1.2 Other design requirements . 8
6.2 Types. 8
6.3 Connections .10
7 Back pressure supports .11
7.1 General .11
7.2 Opening back pressure supports .11
7.3 Non-opening back pressure supports .11
8 Temperature shields .11
9 Stiffening rings .11
10 Gaskets/seals .11
11 Assembly of bursting disc safety devices .11
11.1 General .11
11.2 Bursting disc safety devices with replaceable bursting disc assemblies .12
11.3 Bursting disc safety devices with non-replaceable bursting disc assemblies .12
12 Specified bursting pressure requirements .12
13 Inspection by the manufacturer .13
14 Test procedures .14
14.1 General .14
14.2 Pressure testing .14
14.3 Burst testing .14
14.3.1 General.14
14.3.2 Coincident temperature in the range 15 °C to 30 °C .14
14.3.3 Coincident temperature above or below the range 15 °C to 30 °C .14
14.3.4 Procedure for burst testing .15
14.4 Leak testing .16
14.4.1 General.16
14.4.2 Selection of acceptable leakage rate .16
14.5 Non-destructive examination .16
15 Certification .16
16 Product designation .17
© ISO 2018 – All rights reserved iii

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SIST EN ISO 4126-2:2019
ISO 4126-2:2018(E)

17 Marking .17
17.1 General .17
17.2 Bursting discs or bursting disc assemblies .17
17.3 Bursting disc holders .18
17.4 Bursting disc safety devices with non-replaceable bursting disc assemblies .18
17.5 Ancillary components .19
17.6 Omission of markings .19
18 Packaging and storage .19
Annex A (informative) Packaging: marking, assembly instructions and documentation .20
iv © ISO 2018 – All rights reserved

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SIST EN ISO 4126-2:2019
ISO 4126-2:2018(E)

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 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 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 185, Safety devices for protection against
excessive pressure.
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.
This second edition cancels and replaces the first edition (ISO 4126-2:2003), which has been technically
revised. The main changes compared to the previous edition are as follows:
— non-applicable references have been removed;
— material references (old Annexes A and B) have been removed;
— new Annex A has been added.
A list of all parts in the ISO 4126 series can be found on the ISO website.
© ISO 2018 – All rights reserved v

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SIST EN ISO 4126-2:2019
ISO 4126-2:2018(E)

Introduction
A bursting disc safety device is a non-reclosing pressure relief device used to protect pressure
equipment such as pressure vessels, piping, gas cylinders or other enclosures from excessive pressure
and/or excessive vacuum.
A bursting disc safety device typically comprises an assembly of components including a bursting
disc, a bursting disc holder and, where necessary, other components such as back pressure supports,
stiffening rings, etc.
The bursting disc is the pressure-sensitive part of the bursting disc safety device and is designed to
open by bursting at a specified pressure. There are many different types of bursting disc safety devices
manufactured in corrosion resistant materials, both metallic and non-metallic, to cover a wide range of
nominal sizes, burst pressures and temperatures.
vi © ISO 2018 – All rights reserved

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SIST EN ISO 4126-2:2019
INTERNATIONAL STANDARD ISO 4126-2:2018(E)
Safety devices for protection against excessive pressure —
Part 2:
Bursting disc safety devices
1 Scope
This document specifies the requirements for bursting disc safety devices.
It includes the requirements for the design, manufacture, inspection, testing, certification, marking,
and packaging.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological 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
bursting disc safety device
non-reclosing pressure relief device actuated by differential pressure and designed to function by
the bursting of the bursting disc(s) (3.3), and which is the complete assembly of installed components
including, where appropriate, the bursting disc holder (3.4)
3.2
bursting disc assembly
complete assembly of components which are installed in the bursting disc holder (3.4) to perform the
desired function
3.3
bursting disc
pressure-sensitive component(s) of a bursting disc safety device (3.1), designed to open by bursting at a
specified bursting pressure (3.11)
Note 1 to entry: It is not considered a pressure-containing part with respect to 4.2.
3.4
bursting disc holder
part of a bursting disc safety device (3.1) which retains the bursting disc assembly (3.2) in position
Note 1 to entry: It is considered a pressure-containing part with respect to 4.2.
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SIST EN ISO 4126-2:2019
ISO 4126-2:2018(E)

3.5
conventional domed bursting disc
bursting disc (3.3) which is domed in the direction of the bursting pressure (3.10)
Note 1 to entry: I.e. where the bursting pressure is applied to the concave side of the bursting disc, see Figure 1.
Note 2 to entry: Also referred to as forward-acting bursting disc.
3.6
slotted lined bursting disc
bursting disc (3.3) made up of two or more layers, at least one of which is slit or slotted to control the
bursting pressure (3.10) of the bursting disc
3.7
reverse domed bursting disc
bursting disc (3.3) which is domed against the direction of the bursting pressure (3.10)
Note 1 to entry: I.e. where the bursting pressure is applied to the convex side of the bursting disc, see Figure 2.
Note 2 to entry: Also referred to as reverse-acting bursting disc.
3.8
flat bursting disc
bursting disc (3.3) having one or more layers, which is flat when installed and can be made of a ductile
or brittle material
3.9
graphite bursting disc
bursting disc (3.3) manufactured from graphite, impregnated graphite, flexible graphite or graphite
composite and designed to burst due to bending or shearing forces
Note 1 to entry: The following definitions apply:
a) Graphite: A crystalline form of the element carbon.
b) Impregnated graphite: Graphite in which the open porosity is impregnated with a filler material.
c) Flexible graphite: A graphite structure formed by the compression of thermally exfoliated graphite
intercalation compounds.
d) Graphite composite: Made up of two or more distinct materials and having different properties to those of
the separate materials and in which the proportion of graphite is over 50 per cent by weight.
3.10
bursting pressure
value of the differential pressure between the upstream side and the downstream side of the bursting
disc (3.3) when it bursts
3.11
specified bursting pressure
bursting pressure (3.10) quoted with a coincident temperature (3.14) when defining the bursting disc
(3.3) requirements
Note 1 to entry: Used in conjunction with a performance tolerance (3.15).
3.12
specified maximum bursting pressure
maximum bursting pressure (3.10) quoted with a coincident temperature (3.14) when defining the
bursting disc (3.3) requirements
Note 1 to entry: Used in conjunction with specified minimum bursting pressure (3.13).
2 © ISO 2018 – All rights reserved

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SIST EN ISO 4126-2:2019
ISO 4126-2:2018(E)

3.13
specified minimum bursting pressure
minimum bursting pressure (3.10) quoted with a coincident temperature (3.14) when defining the
bursting disc (3.3) requirements
Note 1 to entry: Used in conjunction with specified maximum bursting pressure (3.12).
3.14
coincident temperature
temperature of the bursting disc (3.3) associated with a bursting pressure (3.10) and which is the
expected temperature of the bursting disc when it is required to burst
3.15
performance tolerance
range of pressure between the specified minimum bursting pressure (3.13) and the specified maximum
bursting pressure (3.12), or the range of pressure in positive and negative percentages or quantities
which is related to the specified bursting pressure (3.11)
Note 1 to entry: See Figure 9.
3.16
operating pressure
pressure existing at normal operating conditions within the system being protected
3.17
differential back pressure
differential pressure across a bursting disc (3.3) in the opposite direction to the direction of the bursting
pressure (3.10), which is the result of pressure in the discharge system from other sources and/or a
result of vacuum on the upstream side of the bursting disc
3.18
vent area
cross-section area available for discharge of fluid as calculated by the manufacturer
3.19
batch
quantity of bursting discs (3.3) or bursting disc safety devices (3.1) made as a single group of the same
type, size, materials and specified bursting pressure (3.11) requirements where the bursting discs (3.3)
are manufactured from the same lot of material (3.20)
3.20
lot of material
definite quantity of material produced by a single manufacturer under conditions that are presumed
uniform
Note 1 to entry: Lots of the following materials used to manufacture bursting discs are defined as:
a) Metal: Material of the same specification coming from the same heat number, heat treatment batch and
specified thickness with tolerances to an appropriate standard;
b) Graphite and flexible graphite: Material of the same specification grade and quality coming from the same
graphite manufacturer and the same manufacturing process;
c) Impregnated graphite: Graphite of the same lot impregnated with a specific grade of filler material by the
same manufacturing process;
d) Graphite composite: Graphite and specific grades of other constituents coming from the same mix of raw
materials.
© ISO 2018 – All rights reserved 3

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