SIST EN ISO 4126-3:2020
(Main)Safety devices for protection against excessive pressure - Part 3: Safety valves and bursting disc safety devices in combination (ISO 4126-3:2020)
Safety devices for protection against excessive pressure - Part 3: Safety valves and bursting disc safety devices in combination (ISO 4126-3:2020)
This document specifies only the requirements for a product assembled from the in-series combination
of safety valves or CSPRS (controlled safety pressure relief systems) according to ISO 4126-1, ISO 4126-4
and ISO 4126-5, and bursting disc safety devices, according to ISO 4126-2, installed upstream of the
valve within five pipe diameters of the valve inlet. It specifies the design, application and marking
requirements for such products, composed of the bursting disc safety device, a safety valve or CSPRS
and, where applicable, a connecting pipe or spool piece. In addition, it gives a method for establishing
the combination discharge factor used in sizing combinations.
Sicherheitseinrichtungen gegen unzulässigen Überdruck - Teil 3: Sicherheitsventile und Berstscheibeneinrichtungen in Kombination (ISO 4126-3:2020)
Dieses Dokument legt nur die Anforderungen fest an ein Produkt, bestehend aus einer in Reihe geschalteten Kombination von Sicherheitseinrichtungen bzw. gesteuerten Sicherheitsventilen (CSPRS) nach ISO 4126 1, ISO 4126 4 und ISO 4126 5 und Berstscheibeneinrichtungen nach ISO 4126 2, bei der die Berstscheibeneinrichtung in einem Abstand von höchstens 5 Rohrdurchmesser vor der Ventileintrittsseite eingebaut ist. Es legt die Anforderungen für Konstruktion, Anwendung und Kennzeichnung von Produkten fest, die eine Berstscheibeneinrichtung, ein Sicherheitsventil oder ein gesteuertes Sicherheitsventil (CSPRS) und ggf. ein Anschlussrohr- oder Leitungsstück umfassen. Zusätzlich wird ein Verfahren festgelegt, nach dem die bei der Bemessung der Kombination eingesetzte Ausflussziffer bestimmt wird.
Dispositifs de sécurité pour protection contre les pressions excessives - Partie 3: Soupapes de sûreté et dispositifs de sûreté à disque de rupture en combinaison (ISO 4126-3:2020)
Le présent document spécifie seulement les exigences applicables aux combinaisons en série de soupapes de sûreté ou de DSDCS (dispositifs de sécurité à décharge contrôlés contre les surpressions), conformément à l'ISO 4126‑1, à l'ISO 4126‑4 et à l'ISO 4126‑5, et de dispositifs de sûreté à disque de rupture conformément à l'ISO 4126‑2 installés en amont de la soupape à une distance de l'orifice d'entrée de la soupape au plus égale à cinq diamètres de tuyauterie. Il spécifie les exigences de conception, d'application et de marquage de tels produits, composés du dispositif de sûreté à disque de rupture, une soupape de sûreté ou un DSDCS et, le cas échéant, la tuyauterie ou manchette de raccordement. Il donne, en outre, la méthode permettant d'établir le coefficient de débit de la combinaison utilisé pour le dimensionnement des combinaisons.
Naprave za varovanje pred visokim tlakom - 3. del: Varnostni ventili in razpočne plošče v kombinaciji (ISO/FDIS 4126-3:2020)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 4126-3:2020
01-november-2020
Nadomešča:
SIST EN ISO 4126-3:2006
Naprave za varovanje pred visokim tlakom - 3. del: Varnostni ventili in razpočne
plošče v kombinaciji (ISO/FDIS 4126-3:2020)
Safety devices for protection against excessive pressure - Part 3: Safety valves and
bursting disc safety devices in combination (ISO 4126-3:2020)
Sicherheitseinrichtungen gegen unzulässigen Überdruck - Teil 3: Sicherheitsventile und
Berstscheibeneinrichtungen in Kombination (ISO 4126-3:2020)
Dispositifs de sécurité pour protection contre les pressions excessives - Partie 3:
Soupapes de sûreté et dispositifs de sûreté à disque de rupture en combinaison (ISO
4126-3:2020)
Ta slovenski standard je istoveten z: EN ISO 4126-3:2020
ICS:
13.240 Varstvo pred previsokim Protection against excessive
tlakom pressure
SIST EN ISO 4126-3:2020 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 4126-3:2020
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SIST EN ISO 4126-3:2020
EN ISO 4126-3
EUROPEAN STANDARD
NORME EUROPÉENNE
September 2020
EUROPÄISCHE NORM
ICS 13.240 Supersedes EN ISO 4126-3:2006
English Version
Safety devices for protection against excessive pressure -
Part 3: Safety valves and bursting disc safety devices in
combination (ISO 4126-3:2020)
Dispositifs de sécurité pour protection contre les Sicherheitseinrichtungen gegen unzulässigen
pressions excessives - Partie 3: Soupapes de sûreté et Überdruck - Teil 3: Sicherheitsventile und
dispositifs de sûreté à disque de rupture en Berstscheibeneinrichtungen in Kombination (ISO
combinaison (ISO 4126-3:2020) 4126-3:2020)
This European Standard was approved by CEN on 11 July 2020.
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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, 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
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 4126-3:2020 E
worldwide for CEN national Members.
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SIST EN ISO 4126-3:2020
EN ISO 4126-3:2020 (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
2
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SIST EN ISO 4126-3:2020
EN ISO 4126-3:2020 (E)
European foreword
This document (EN ISO 4126-3:2020) 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 March 2021, and conflicting national standards shall
be withdrawn at the latest by March 2021.
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 4126-3:2006.
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, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 4126-3:2020 has been approved by CEN as EN ISO 4126-3:2020 without any
modification.
3
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SIST EN ISO 4126-3:2020
EN ISO 4126-3:2020 (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 2.1 5, 7, 9 and 12 General design
Clause 2.11.1 and 2.11.2 5, 6, 7, 8, 9, 11 and 12 Safety accessories
Clause 3.4 a), 1st indent 6 Installation instructions
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.
4
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SIST EN ISO 4126-3:2020
INTERNATIONAL ISO
STANDARD 4126-3
Second edition
2020-09
Safety devices for protection against
excessive pressure —
Part 3:
Safety valves and bursting disc safety
devices in combination
Dispositifs de sécurité pour protection contre les pressions
excessives —
Partie 3: Soupapes de sûreté et dispositifs de sûreté à disque de
rupture en combinaison
Reference number
ISO 4126-3:2020(E)
©
ISO 2020
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SIST EN ISO 4126-3:2020
ISO 4126-3:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
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
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
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SIST EN ISO 4126-3:2020
ISO 4126-3:2020(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 4
5 Design of combination . 4
6 Installation of combination . 5
7 Combination performance . 5
8 Determination of combination discharge capacity factor, F , by testing.6
d
8.1 General . 6
8.2 Test requirements . 6
8.3 Test rig . 6
8.4 Test method . 7
8.5 Test procedure . 7
8.6 Acceptance criteria of the tests . 7
8.6.1 General. 7
8.6.2 Conditions applicable to the safety valve . 8
8.6.3 Conditions applicable to the bursting disc safety device . 8
8.6.4 Conditions applicable to combination . 8
9 Derivation of combination discharge capacity factor, F . 9
d
10 Alternative to testing for F . 9
d
11 Certification of combination discharge capacity factor, F . 9
d
12 Application and use of the certified combination discharge capacity factor, F .9
d
13 Marking and identification of combination devices . 9
13.1 Bursting disc safety device . 9
13.2 Safety valve .10
13.3 Combination .10
14 Documentation .10
15 Preparation for storage and transport .11
© ISO 2020 – All rights reserved iii
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SIST EN ISO 4126-3:2020
ISO 4126-3:2020(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, in collaboration with the European Committee for Standardization (CEN) Technical
Committee CEN/TC 69, Industrial valves, in accordance with the Agreement on technical cooperation
between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 4126-3:2006), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— Eliminated unnecessary references and definitions throughout the document.
— Clause 5: Inlet line and pressure drop requirements from prior 6.2 were moved to Clause 5 and a
reference to ISO 4126-9 was also added.
— Clause 7: Deleted specific references to specific EN standards to refer to the applicable pressure
vessel standard to reflect the global nature of this document.
— Clause 9: The restrictions for F values less than 0,97 were eliminated.
d
— Clause 12: Clarified the applicable minimum bursting pressure for which the F value can be used
d
for sizes larger than those flow tested.
— Clause 14: Added a requirement for the supplier to provide a test certificate if the F being used is a
d
certified combination discharge coefficient.
A list of all parts in the ISO 4126 series can be found on the ISO website.
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.
iv © ISO 2020 – All rights reserved
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SIST EN ISO 4126-3:2020
ISO 4126-3:2020(E)
Introduction
Bursting disc safety devices can be used upstream of safety valves in the following cases:
a) to protect the safety valve against corrosion, fouling or operating conditions which could affect the
safety valve performance;
b) to prevent leakage;
c) to prevent total loss of contents from the protected equipment following the bursting of the
bursting disc.
The term combination is used to describe the close-coupled (i.e. within 5 pipe diameters) assembly of
a bursting disc safety device upstream of a safety valve or controlled safety pressure relief systems
(CSPRS), as defined by this document. Requirements for other installation arrangements of bursting
discs with safety valves or CSPRS are defined in ISO 4126-9.
© ISO 2020 – All rights reserved v
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SIST EN ISO 4126-3:2020
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SIST EN ISO 4126-3:2020
INTERNATIONAL STANDARD ISO 4126-3:2020(E)
Safety devices for protection against excessive pressure —
Part 3:
Safety valves and bursting disc safety devices in
combination
1 Scope
This document specifies only the requirements for a product assembled from the in-series combination
of safety valves or CSPRS (controlled safety pressure relief systems) according to ISO 4126-1, ISO 4126-4
and ISO 4126-5, and bursting disc safety devices, according to ISO 4126-2, installed upstream of the
valve within five pipe diameters of the valve inlet. It specifies the design, application and marking
requirements for such products, composed of the bursting disc safety device, a safety valve or CSPRS
and, where applicable, a connecting pipe or spool piece. In addition, it gives a method for establishing
the combination discharge factor used in sizing combinations.
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 4126-1:2013, Safety devices for protection against excessive pressure — Part 1: Safety valves
ISO 4126-2:2018, Safety devices for protection against excessive pressure — Part 2: Bursting disc
safety devices
ISO 4126-4:2013, Safety devices for protection against excessive pressure — Part 4: Pilot operated
safety valves
ISO 4126-5:2013, Safety devices for protection against excessive pressure — Part 5: Controlled safety
pressure relief systems (CSPRS)
ISO 4126-6:2014, Safety devices for protection against excessive pressure — Part 6: Application, selection
and installation of bursting disc safety devices
ISO 4126-9:2008, Safety devices for protection against excessive pressure — Part 9: Application and
installation of safety devices excluding stand-alone bursting disc safety devices
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/
© ISO 2020 – All rights reserved 1
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SIST EN ISO 4126-3:2020
ISO 4126-3:2020(E)
3.1
combination
installation which comprises a bursting disc safety device (3.3) installed within five pipe diameters
(from outlet of bursting disc holder (3.6) to inlet of valve) before the inlet of a safety valve or a CSPRS
Note 1 to entry: See Figure 1.
Key
1 safety valve or CSPRS
2 bursting disc safety device
3 safety valve or CSPRS inlet
4 bursting disc safety device outlet
NOTE Other bursting disc safety device configurations used in conjunction with safety valves or CSPRS are
specified in ISO 4126-6.
Figure 1 — Diagram of combination showing relative distance
3.2
combination discharge capacity factor
F
d
factor used to determine the discharge capacity of a safety valve or CSPRS when the safety valve or
CSPRS is used in combination with a bursting disc safety device (3.3) installed upstream of the safety
valve or CSPRS
3.3
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) (3.5)
Note 1 to entry: It is the complete assembly of installed components including, where appropriate, the bursting
disc holder (3.6).
3.4
bursting disc assembly
complete assembly of the components installed in the bursting disc holder (3.6) to perform the desired
function
3.5
bursting disc
pressure-sensitive component(s) of a bursting disc safety device (3.3) designed to open by bursting at a
specified bursting pressure (3.7)
3.6
bursting disc holder
part of a bursting disc safety device (3.3) which retains the bursting disc assembly (3.4) in position
2 © ISO 2020 – All rights reserved
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SIST EN ISO 4126-3:2020
ISO 4126-3:2020(E)
3.7
specified bursting pressure
bursting pressure (3.13) quoted with a coincident temperature when defining the bursting disc (3.5)
requirements
Note 1 to entry: It is used in conjunction with a performance tolerance (3.10).
3.8
specified maximum bursting pressure
maximum bursting pressure (3.13) quoted with the coincident temperature when defining the bursting
disc (3.5) requirements
Note 1 to entry: It is used in conjunction with a specified minimum bursting pressure (3.9).
3.9
specified minimum bursting pressure
minimum bursting pressure (3.13) quoted with the coincident temperature when defining the bursting
disc (3.5) requirements
Note 1 to entry: It is used in conjunction with a specified maximum bursting pressure (3.8).
3.10
performance tolerance
range of pressure between the specified minimum bursting pressure (3.9) and the specified maximum
bursting pressure (3.8) or the range of pressure in positive and negative percentages or quantities which
is related to the specified bursting pressure (3.7)
3.11
relieving pressure
maximum pressure under discharge conditions in the pressurised system
Note 1 to entry: It may differ from the bursting pressure of the bursting disc (3.5).
3.12
batch
quantity of bursting discs or bursting disc safety devices (3.3) made as a single group of the same type,
size, materials and specified bursting pressure (3.7) requirements, and where the bursting discs (3.5) are
manufactured from the same lot of material
3.13
bursting pressure
value of the differential pressure between the upstream side and the downstream side of the bursting
disc (3.5) when it bursts
3.14
pressure relief system
system intended for the safe relief of fluids from pressure equipment for prevention of excessive
pressure
Note 1 to entry: It can consist of equipment nozzle, inlet piping, pressure relief device(s) and discharge piping to
atmosphere/collecting vessel/header.
3.15
certified derated coefficient of discharge
K
dr
adjusted coefficient of discharge (3.16) for the safety valve or CSPRS
Note 1 to entry: See ISO 4126-1, ISO 4126-4, or ISO 4126-5 as applicable.
© ISO 2020 – All rights reserved 3
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SIST EN ISO 4126-3:2020
ISO 4126-3:2020(E)
3.16
coefficient of discharge
K
d
value of actual discharge capacity (from tests) divided by the theoretical discharge capacity (from
calculation) of the safety valve or CSPRS.
Note 1 to entry: See ISO 4126-1, ISO 4126-4, or ISO 4126-5 as applicable.
3.17
combination coefficient of discharge
K
dc
tested value of actual discharge capacity of the combination (3.1) divided by the theoretical discharge
capacity of the safety valve or CSPRS
3.18
set pressure
P
set
predetermined pressure at which a safety valve or CSPRS under operating conditions commences to open
Note 1 to entry: It is the gauge pressure measured at the valve inlet at which the pressure forces tending to open
the valve for the specific service conditions are in equilibrium with the forces retaining the valve disc on its seat.
4 Symbols
A flow area of a safety valve (not curtain area), in square millimetres
F combination discharge capacity factor
d
K coefficient of discharge of the safety valve or CSPRS
d
K combination coefficient of discharge
dc
K certified derated coefficient of discharge for safety valve or CSPRS
dr
P set pressure of safety valve or CSPRS
set
5 Design of combination
Bursting disc safety devices shall comply with ISO 4126-2.
Application and selection of bursting disc safety devices shall be in accordance with ISO 4126-6.
Safety valves shall comply with ISO 4126-1 or ISO 4126-4.
CSPRS shall comply with ISO 4126-5.
Where additional components are used to combine the bursting disc safety device and the safety valve
or CSPRS into a combination (e.g. spool piece), these shall comply with the applicable design standard.
The connection from the protected equipment to the safety valve inlet shall be as short as practicable
and designed so that the total pressure drop to the safety valve or CSPRS inlet, including the effect of
the bursting disc safety device, shall meet the requirements for the inlet line as described in ISO 4126-9.
Calculate the total inlet pressure drop (difference of stagnation pressures, i.e. non-recoverable losses)
using the actual flowing capacity, which is the capacity of the safety device calculated using the certified
coefficient of discharge, divided by the derating factor 0,9 and multiplied by the certified combination
discharge capacity factor F or a value of F = 1,0 if a certified value is not available. Please be aware of
d d
4 © ISO 2020 – All rights reserved
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SIST EN ISO 4126-3:2020
ISO 4126-3:2020(E)
national codes or regulations regarding the total inlet pressure drop. The pressure drop shall include
the effects of isolating valves, fittings and bursting disc safety devices.
NOTE 1 This guidance is not intended to cause a redesign of existing systems that have demonstrated stable
operation during valve discharge.
The space between the bursting disc safety device and the safety valve or CSPRS shall be provided with
a connection to prevent or detect an unacceptable build up in pressure.
NOTE 2 Bursting discs, being pressure-differential devices, require a higher pressure in the protected
equipment to burst the bursting disc if pressure builds up in the space between the bursting disc and the safety
valve or the CSPRS. This occurs when leakage develops through the bursting disc due to corrosion, due to back
pressure in the discharge piping or other cause.
After bursting, the bursting disc petals shall not protrude into the valve inlet unless the influence of the
petals on the capacity and performance of the safety valve or CSPRS have been assessed and proven to
meet the requirements of Clause 7.
The design of the bursting disc safety device shall be such that on bursting, release of bursting disc
material shall not impair the performance of the safety valve or the CSPRS.
The nominal pipe size of the bursting disc safety device shall be not less than the nominal size of the
inlet of the safety valve or CSPRS.
6 Installation of combination
The discharge of the combination shall be disposed of safely and be prevented from unintentional
flowing into other equipment to create a hazard (for example, into equipment out of service or
undergoing maintenance). The discharge pipe, between the outlet of the combination and the
atmosphere or venting system, shall always be adequately drained to prevent accumulation of liquids.
Provisions shall be made to absorb the reaction forces expected during the discharge of material.
The supplier of the combination shall provide a
...
SLOVENSKI STANDARD
oSIST prEN ISO 4126-3:2019
01-oktober-2019
Naprave za varovanje pred visokim tlakom - 3. del: Varnostni ventili in razpočne
plošče v kombinaciji (ISO/DIS 4126-3:2019)
Safety devices for protection against excessive pressure - Part 3: Safety valves and
bursting disc safety devices in combination (ISO/DIS 4126-3:2019)
Sicherheitseinrichtungen gegen unzulässigen Überdruck - Teil 3: Sicherheitsventile und
Berstscheibeneinrichtungen in Kombination (ISO/DIS 4126-3:2019)
Dispositifs de sécurité pour protection contre les pressions excessives - Partie 3:
Soupapes de sûreté et dispositifs de sûreté à disque de rupture en combinaison
(ISO/DIS 4126-3:2019)
Ta slovenski standard je istoveten z: prEN ISO 4126-3
ICS:
13.240 Varstvo pred previsokim Protection against excessive
tlakom pressure
oSIST prEN ISO 4126-3:2019 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
oSIST prEN ISO 4126-3:2019
---------------------- Page: 2 ----------------------
oSIST prEN ISO 4126-3:2019
DRAFT INTERNATIONAL STANDARD
ISO/DIS 4126-3
ISO/TC 185 Secretariat: ANSI
Voting begins on: Voting terminates on:
2019-08-05 2019-10-28
Safety devices for protection against excessive pressure —
Part 3:
Safety valves and bursting disc safety devices in
combination
Dispositifs de sécurité pour protection contre les pressions excessives —
Partie 3: Soupapes de sûreté et dispositifs de sûreté à disque de rupture en combinaison
ICS: 13.240
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 4126-3:2019(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
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oSIST prEN ISO 4126-3:2019
ISO/DIS 4126-3:2019(E)
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oSIST prEN ISO 4126-3:2019
ISO/DIS 4126-3:2019(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 4
5 Design of combination . 4
6 Installation of combination . 5
7 Combination performance . 5
8 Determination of combination discharge capacity factor, F , by testing .6
d
8.1 General . 6
8.2 Test requirements . 6
8.3 Test rig . 7
8.4 Test method . 7
8.5 Test procedure . 7
8.6 Acceptance criteria of the tests . 8
8.6.1 General. 8
8.6.2 Conditions applicable to the safety valve . 8
8.6.3 Conditions applicable to the bursting disc safety device . 8
8.6.4 Conditions applicable to combination . 8
9 Derivation of combination discharge capacity factor, F . 9
d
10 Alternative to testing for F . 9
d
11 Certification of combination discharge capacity factor, F . 9
d
12 Application and use of the certified combination discharge capacity factor, F .9
d
13 Marking and identification of combination devices . 9
13.1 Bursting disc safety device . 9
13.2 Safety valve .10
13.3 Combination .10
14 Documentation .10
15 Preparation for storage and transport .10
Annex ZA (informative) Relationship between this European Standard and the Essential
Requirements of EU Directive 2014/68/EU (PED) aimed to be covered .11
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oSIST prEN ISO 4126-3:2019
ISO/DIS 4126-3:2019(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 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 185, Safety devices for protection against
excessive pressure.
This second edition cancels and replaces the first edition (ISO 4126-3:2006), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— Throughout: Eliminated unnecessary references and definitions
— Clause 5: Inlet line and pressure drop requirements from prior clause 6.2 were moved to Clause 5
and a reference to ISO 4126-9 was also added.
— Clause 7: Deleted specific references to specific EN standards to refer to the applicable pressure
vessel standard to reflect the global nature of this standard.
— Clause 9: The restrictions for F values less than 0,97 were eliminated.
d
— Clause 12: Clarified the applicable minimum bursting pressure for which the F value can be used
d
for sizes larger than those flow tested.
— Clause 14: Added a requirement for the supplier to provide a test certificate if the F being used is a
d
certified combination discharge coefficient.
A list of all parts in the ISO 4126- series can be found on the ISO website.
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oSIST prEN ISO 4126-3:2019
ISO/DIS 4126-3:2019(E)
Introduction
Bursting disc safety devices can be used upstream of safety valves in the following cases:
a) to protect the safety valve against corrosion, fouling or operating conditions which could affect the
safety valve performance;
b) to prevent leakage;
c) to prevent total loss of contents from the protected equipment following the bursting of the
bursting disc.
The term combination is used to describe the close-coupled (i.e. within 5 pipe diameters) assembly of
a bursting disc safety device upstream of a safety valve or CSPRS, as defined by the part of ISO 4126.
Requirements for other installation arrangements of bursting discs with safety valves or CSPRS are
defined in ISO 4126-9.
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oSIST prEN ISO 4126-3:2019
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oSIST prEN ISO 4126-3:2019
DRAFT INTERNATIONAL STANDARD ISO/DIS 4126-3:2019(E)
Safety devices for protection against excessive pressure —
Part 3:
Safety valves and bursting disc safety devices in
combination
1 Scope
This part of ISO 4126 specifies only the requirements for a product assembled from the in series
combination of safety valves or CSPRS (controlled safety pressure relief systems) according to
ISO 4126-1, ISO 4126-4 and ISO 4126-5, and bursting disc safety devices according to ISO 4126-2
installed upstream of the valve within five pipe diameters of the valve inlet. It specifies the design,
application and marking requirements for such products, composed of the bursting disc safety device,
a safety valve or CSPRS and, where applicable, a connecting pipe or spool piece. In addition, it gives a
method for establishing the combination discharge factor used in sizing combinations.
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 4126-1, Safety devices for protection against excessive pressure — Part 1: Safety valves
ISO 4126-2, Safety devices for protection against excessive pressure — Part 2: Bursting disc safety devices
ISO 4126-4, Safety devices for protection against excessive pressure — Part 4: Pilot operated safety valves
ISO 4126-5, Safety devices for protection against excessive pressure — Part 5: Controlled safety pressure
relief systems (CSPRS)
ISO 4126-6, Safety devices for protection against excessive pressure — Part 6: Application, selection and
installation of bursting disc safety devices
ISO 4126-7, Safety devices for protection against excessive pressure — Part 7: Common data
ISO 4126-9, Safety devices for protection against excessive pressure — Part 9: Application and installation
of safety devices excluding stand-alone bursting disc safety devices
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:
— IEC Electropedia: available at http: //www .electropedia .org/
— ISO Online browsing platform: available at https: //www .iso .org/obp
3.1
combination
installation which comprises a bursting disc safety device installed within five pipe diameters (from
outlet of bursting disc holder to inlet of valve) before the inlet of a safety valve or a CSPRS
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oSIST prEN ISO 4126-3:2019
ISO/DIS 4126-3:2019(E)
SEE: Figure 1.
Key
1. safety valve or CSPRS
2. bursting disc safety device
3. safety valve or CSPRS inlet
4. bursting disc safety device outlet
NOTE Other bursting disc safety device configurations used in conjunction with safety valves or CSPRS are
specified in ISO 4126-6.
Figure 1 — Diagram of combination showing relative distance
3.2
combination discharge capacity factor
F
d
factor used to determine the discharge capacity of a safety valve or CSPRS when the safety valve or
CSPRS is used in combination with a bursting disc safety device installed upstream of the safety valve
or CSPRS
3.3
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)
Note 1 to entry: It is the complete assembly of installed components including, where appropriate, the bursting
disc holder.
3.4
bursting disc assembly
complete assembly of the components installed in the bursting disc holder to perform the desired
function
3.5
bursting disc
pressure-sensitive component(s) of a bursting disc safety device, designed to open by bursting at a
specified bursting pressure
3.6
bursting disc holder
part of a bursting disc safety device which retains the bursting disc assembly in position
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3.7
specified bursting pressure
bursting pressure quoted with a coincident temperature when defining the bursting disc requirements
Note 1 to entry: It is used in conjunction with a performance tolerance (3.10)
3.8
specified maximum bursting pressure
maximum bursting pressure quoted with the coincident temperature when defining the bursting disc
requirements
Note 1 to entry: It is used in conjunction with a specified minimum bursting pressure (3.9)
3.9
specified minimum bursting pressure
minimum bursting pressure quoted with the coincident temperature when defining the bursting disc
requirements
Note 1 to entry: It is used in conjunction with a specified maximum bursting pressure (3.8)
3.10
performance tolerance
range of pressure between the specified minimum bursting pressure and the specified maximum
bursting pressure or the range of pressure in positive and negative percentages or quantities which is
related to the specified bursting pressure
3.11
operating pressure
pressure existing at normal operating conditions within the system being protected
3.12
relieving pressure
maximum pressure under discharge conditions in the pressurised system
Note 1 to entry: It may differ from the bursting pressure of the bursting disc.
3.13
bursting disc safety device discharge area
minimum cross-sectional flow area of the bursting disc safety device, taking into consideration the
possible reduction of the cross-section by, for example, back pressure supports, catching devices or
parts of the bursting disc which remain after bursting
3.14
batch
quantity of bursting discs or bursting disc safety devices made as a single group of the same type,
size, materials and specified bursting pressure requirements, and where the bursting discs are
manufactured from the same lot of material
3.15
bursting pressure
value of the differential pressure between the upstream side and the downstream side of the bursting
disc when it bursts
3.16
bursting disc safety device discharge capacity
rate at which a bursting disc safety device can discharge fluid after bursting of the bursting disc
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3.17
pressure relief system
system intended for the safe relief of fluids from pressure equipment for prevention of excessive
pressure
Note 1 to entry: It can consist of equipment nozzle, inlet piping, pressure relief device(s) and discharge piping to
atmosphere/collecting vessel/header.
3.18
certified derated coefficient of discharge
adjusted coefficient of discharge for the safety valve
Note 1 to entry: Note1 to entry: See ISO 4126-7.
3.19
coefficient of discharge
K
d
Value of actual discharge capacity (from tests) divided by the theoretical discharge capacity (from
calculation)
3.20
set pressure
P
set
predetermined pressure at which a safety valve or CSPRS under operating conditions commences to open
Note 1 to entry: It is the gauge pressure measured at the valve inlet at which the pressure forces tending to open
the valve for the specific service conditions are in equilibrium with the forces retaining the valve disc on its seat.
4 Symbols
A flow area of a safety valve (not curtain area), in square millimetres
F combination discharge capacity factor
d
K coefficient of discharge of the safety valve or CSPRS
d
K c
...
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