SIST EN ISO 4126-1:2013
(Main)Safety devices for protection against excessive pressure - Part 1: Safety valves (ISO 4126-1:2013)
Safety devices for protection against excessive pressure - Part 1: Safety valves (ISO 4126-1:2013)
ISO 4126-1:2013 specifies general requirements for safety valves irrespective of the fluid for which they are designed.
It is applicable to safety valves having a flow diameter of 4 mm and above which are for use at set pressures of 0,1 bar gauge and above. No limitation is placed on temperature.
ISO 4126-1:2013 is a product standard and is not applicable to applications of safety valves.
Sicherheitseinrichtungen gegen unzulässigen Überdruck - Teil 1: Sicherheitsventile (ISO 4126-1:2013)
Diese Europäische Norm legt allgemeine Anforderungen an Sicherheitsventile fest, unabhängig von dem Medium, für das sie ausgelegt sind.
Die Norm gilt für Sicherheitsventile mit einem engsten Strömungsdurchmesser von mindestens 4 mm und für Ansprech¬drücke von mindestens 0,1 bar. Temperaturgrenzen sind nicht festgelegt.
Die vorliegende Norm ist eine Produktnorm und behandelt keine Anwendungsfälle für Sicherheitsventile.
Dispositifs de sécurité pour protection contre les pressions excessives - Partie 1: Soupapes de sûreté (ISO 4126-1:2013)
L'ISO 4126-1:2013 spécifie les exigences générales des soupapes de sûreté, quel que soit le fluide pour lequel elles sont conçues.
Elle est applicable aux soupapes de sûreté présentant un orifice d'écoulement de diamètre supérieur ou égal à 4 mm, qui sont utilisables à des pressions de début d'ouverture de 0,1 bar effectif et au-dessus. Aucune limitation en température n'est fixée.
L'ISO 4126-1:2013 est une norme de produit et elle n'est pas applicable à la mise en ?uvre des soupapes de sûreté.
Naprave za varovanje pred visokim tlakom - 1. del: Varnostni ventili (ISO 4126-1:2013)
Ta del standarda ISO 4126 določa splošne zahteve za varnostne ventile ne glede na tekočino, za katero so oblikovani. Uporablja se za varnostne ventile s premerom pretoka 4 mm in več, ki se uporabljajo pri nastavljenih tlakih 0,1 bara in več. Temperatura ni omejena. To je standard izdelka in ne velja za uporabo varnostnih ventilov.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-september-2013
1DGRPHãþD
SIST EN ISO 4126-1:2004
SIST EN ISO 4126-1:2004/AC:2007
Naprave za varovanje pred visokim tlakom - 1. del: Varnostni ventili (ISO 4126-
1:2013)
Safety devices for protection against excessive pressure - Part 1: Safety valves (ISO
4126-1:2013)
Sicherheitseinrichtungen gegen unzulässigen Überdruck - Teil 1: Sicherheitsventile (ISO
4126-1:2013)
Dispositifs de sécurité pour protection contre les pressions excessives - Partie 1:
Soupapes de sûreté (ISO 4126-1:2013)
Ta slovenski standard je istoveten z: EN ISO 4126-1:2013
ICS:
13.240 Varstvo pred previsokim Protection against excessive
tlakom pressure
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD
EN ISO 4126-1
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2013
ICS 13.240 Supersedes EN ISO 4126-1:2004
English Version
Safety devices for protection against excessive pressure - Part
1: Safety valves (ISO 4126-1:2013)
Dispositifs de sécurité pour protection contre les pressions Sicherheitseinrichtungen gegen unzulässigen Überdruck -
excessives - Partie 1: Soupapes de sûreté (ISO 4126- Teil 1: Sicherheitsventile (ISO 4126-1:2013)
1:2013)
This European Standard was approved by CEN on 28 December 2012.
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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2013 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 4126-1:2013: E
worldwide for CEN national Members.
Contents Page
Foreword .3
Annex ZA (informative) Relationship between this International Standard and the Essential
Requirements of EU Directive 97/23/EC (PED) .4
Foreword
This document (EN ISO 4126-1:2013) 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 January 2014, and conflicting national standards shall be withdrawn at
the latest by January 2014.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 4126-1:2004.
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 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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.
Endorsement notice
The text of ISO 4126-1:2013 has been approved by CEN as EN ISO 4126-1:2013 without any modification.
Annex ZA
(informative)
Relationship between this International Standard and the
Essential Requirements of EU Directive 97/23/EC (PED)
By agreement between ISO and CEN, this CEN annex is included in the DIS and the FDIS but will not appear
in the published ISO standard.
This International Standard has been prepared under a mandate given to CEN by the European Commission
and the European Free Trade Association to provide one means of conforming to Essential Requirements of
the New Approach Directive 97/23/EC (PED).
Once this standard is cited in the Official Journal of the European Communities under that Directive and has
been implemented as a national standard in at least one Member State, compliance with the normative
clauses of this standard given in Table ZA.1 confers, within the limits of the scope of this standard, a
presumption of conformity with the corresponding Essential Requirements of that Directive and associated
EFTA regulations.
Table ZA.1 — Correspondence between this International Standard and Directive 97/23/EC (PED)
Sub-clauses of this International Essential Requirements of Directive 97/23/EC (PED)
Standard
Essential Requirements Annex I of PED
5,6,7,8,9 Safety accessories 2.11.1
5.1.5 Safety of operation 2.3
5.1.6 Drain and venting 2.5
6.3 Proof test 3.2.2
10 Marking and labelling 3.3
WARNING: Other requirements and other EU Directives may be applicable to the products falling within the
scope of this standard.
INTERNATIONAL ISO
STANDARD 4126-1
Third edition
2013-07-15
Safety devices for protection against
excessive pressure —
Part 1:
Safety valves
Dispositifs de sécurité pour protection contre les pressions excessives —
Partie 1: Soupapes de sûreté
Reference number
ISO 4126-1:2013(E)
©
ISO 2013
ISO 4126-1:2013(E)
© ISO 2013
All rights reserved. Unless otherwise specified, 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
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2013 – All rights reserved
ISO 4126-1:2013(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and units . 4
5 Design . 4
5.1 General . 4
5.2 Valve end connections . 5
5.3 Minimum requirements for springs . 5
5.4 Materials . 6
6 Production testing . 6
6.1 Purpose . 6
6.2 General . 6
6.3 Hydrostatic testing . 6
6.4 Pneumatic testing . 7
6.5 Adjustment of set or cold differential test pressure . 8
6.6 Seat leakage test. 8
7 Type testing. 8
7.1 General . 8
7.2 Tests to determine operating characteristics . 9
7.3 Tests to determine flow characteristics.11
7.4 Determination of the coefficient of discharge .12
7.5 Certification of coefficient of discharge .12
8 Determination of safety valve performance .13
9 Sizing of safety valves .13
10 Marking and sealing .13
10.1 Marking .13
10.2 Sealing of a safety valve .13
Bibliography .14
ISO 4126-1:2013(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International
Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies
casting a vote.
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.
ISO 4126-1 was prepared by Technical Committee ISO/TC 185, Safety devices for protection against
excessive pressure.
This third edition cancels and replaces the second edition (ISO 4126-1:2004), which has been technically
revised. It also incorporates the Technical Corrigendum ISO 4126-1:2004/Cor.1:2007.
ISO 4126 consists of the following parts, under the general title Safety devices for protection against
excessive pressure:
— Part 1: Safety valves
— Part 2: Bursting disc safety devices
— Part 3: Safety valves and bursting disc safety devices in combination
— Part 4: Pilot operated safety valves
— Part 5: Controlled safety pressure relief systems (CSPRS)
— Part 6: Application, selection and installation of bursting disc safety devices
— Part 7: Common data
— Part 9: Application and installation of safety devices excluding stand-alone bursting disc safety devices
— Part 10: Sizing of safety valves for gas/liquid two-phase flow
1)
— Part 11: Performance testing
Part 7 contains data that is common to more than one of the parts of ISO 4126 to avoid unnecessary repetition.
1) Under preparation.
iv © ISO 2013 – All rights reserved
INTERNATIONAL STANDARD ISO 4126-1:2013(E)
Safety devices for protection against excessive pressure —
Part 1:
Safety valves
1 Scope
This part of ISO 4126 specifies general requirements for safety valves irrespective of the fluid for which
they are designed.
It is applicable to safety valves having a flow diameter of 4 mm and above which are for use at set
pressures of 0,1 bar gauge and above. No limitation is placed on temperature.
This is a product standard and is not applicable to applications of safety valves.
2 Normative references
The following referenced documents are indispensable for the application 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 4126-7:2013, Safety devices for protection against excessive pressure — Part 7: Common data
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
safety valve
valve which automatically, without the assistance of any energy other than that of the fluid concerned,
discharges a quantity of the fluid so as to prevent a predetermined safe pressure being exceeded, and
which is designed to re-close and prevent further flow of fluid after normal pressure conditions of
service have been restored
Note 1 to entry: The valve can be characterized either by pop action (rapid opening) or by opening in proportion
(not necessarily linear) to the increase in pressure over the set pressure.
3.2
direct loaded safety valve
safety valve in which the loading due to the fluid pressure underneath the valve disc is opposed only by
a direct mechanical loading device such as a weight, lever and weight, or spring
3.3
assisted safety valve
safety valve which, by means of a powered assistance mechanism, may additionally be lifted at a pressure
lower than the set pressure and will, even in the event of failure of the assistance mechanism, comply
with all the requirements for safety valves given in ISO 4126
ISO 4126-1:2013(E)
3.4
supplementary loaded safety valve
safety valve which has, until the pressure at the inlet to the safety valve reaches the set pressure, an
additional force which increases the sealing force
Note 1 to entry: This additional force (supplementary load), which may be provided by means of an extraneous
power source, is reliably released when the pressure at the inlet of the safety valve reaches the set pressure. The
amount of supplementary loading is so arranged that if such supplementary loading is not released, the safety
valve will attain its certified discharge capacity at a pressure not greater than 1,1 times the maximum allowable
pressure of the equipment to be protected.
Note 2 to entry: Other types of supplementary loaded safety devices are dealt with in ISO 4126-5.
3.5
set pressure
predetermined pressure at which a safety valve 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.
3.6
maximum allowable pressure
PS
maximum pressure for which the protected equipment is designed
3.7
overpressure
pressure increase over the set pressure
Note 1 to entry: Overpressure is usually expressed as a percentage of the set pressure.
3.8
reseating pressure
value of the inlet static pressure at which the disc re-establishes contact with the seat or at which the
lift becomes zero
3.9
cold differential test pressure
inlet static pressure at which a safety valve is set to commence to open on the test bench
Note 1 to entry: This test pressure includes corrections for service conditions, e.g. back pressure and/or temperature.
3.10
relieving pressure
pressure used for the sizing of a safety valve which is greater than or equal to the set pressure plus
overpressure
3.11
back pressure
pressure that exists at the outlet of a safety valve as a result of the pressure in the discharge system
Note 1 to entry: The back pressure is the sum of the superimposed and built-up back pressures.
3.12
built-up back pressure
pressure existing at the outlet of a safety valve caused by flow through the valve and the discharge system
3.13
superimposed back pressure
pressure existing at the outlet of a safety valve at the time when the device is required to operate
Note 1 to entry: It is the result of pressure in the discharge system from other sources.
2 © ISO 2013 – All rights reserved
ISO 4126-1:2013(E)
3.14
balanced bellows
device which minimizes the effect of back pressure on the set pressure and/or the operation of a safety valve
3.15
blowdown
difference between set and reseating pressures
Note 1 to entry: Blowdown is normally stated as a percentage of set pressure except for pressures of less than
3 bar when the blowdown is expressed in bar.
3.16
lift
actual travel of the valve disc away from the closed position
3.17
flow area
minimum cross-sectional flow area (but not the smallest area between disc and seat) between inlet and
seat which is used to calculate the theoretical flow capacity, with no deduction for any obstruction
3.18
flow diameter
diameter corresponding to the flow area
3.19
theoretical discharge capacity
calculated capacity expressed in mass or volumetric units of a theoretically perfect nozzle having a
cross-sectional flow area equal to the flow area of a safety valve
3.20
coefficient of discharge
value of actual flowing capacity (from tests) divided by the theoretical flowing capacity (from calculation)
3.21
certified (discharge) capacity
that portion of the measured capacity permitted to be used as a basis for the application of a safety valve
Note 1 to entry: It may, for example, equal the: a) measured flow rate times the derating factor; or b) theoretical
flow rate times the coefficient of discharge times the derating factor; or c) theoretical flow rate times the certified
de-rated coefficient of discharge.
3.22
DN (nominal size)
alphanumeric designation of size that is common for components used in a piping system, used for
reference purposes, comprising the letters DN followed by a dimensionless number having an indirect
correspondence to the physical size of the bore or outside diameter of the component end connection
Note 1 to entry: The dimensionless number does not represent a measurable value and is not used for
calculation purposes.
Note 2 to entry: Prefix DN usage is applicable to components bearing PN designations according to ISO 7268.
Note 3 to entry: Adapted from ISO 6708:1995, definition 2.1.
ISO 4126-1:2013(E)
4 Symbols and units
Table 1 — Symbols and their descriptions
Symbol Description Unit
A Flow area of a safety valve (not smallest area between seat and disc) mm
a
K Coefficient of discharge —
d
a
K Certified de-rated coefficient of discharge (K × 0,9) —
dr d
n Number of tests —
q Theoretical specific discharge capacity kg/(h⋅mm )
m
q′ Specific discharge capacity determined by tests kg/(h⋅mm )
m
a
K and K are expressed as 0,xxx.
d dr
5 Design
5.1 General
5.1.1 The design shall incorporate guiding arrangements necessary to ensure consistent operation
and seat tightness.
5.1.2 The seat of a safety valve, other than when it is an integral part of the valve shell, shall be fastened
securely to prevent the seat becoming loose in service.
5.1.3 In the case of valves where the lift can be reduced to conform to the required discharge capacity,
restriction of the lift shall not interfere with the operation of the valve. The lift restricting device shall be
designed so that, if adjustable, the adjustable feature can be mechanically locked and access sealed. The
lift restricting device shall
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