SIST EN ISO 4126-4:2013
(Main)Safety devices for protection against excessive pressure - Part 4: Pilot-operated safety valves (ISO 4126-4:2013)
Safety devices for protection against excessive pressure - Part 4: Pilot-operated safety valves (ISO 4126-4:2013)
This part of ISO 4126 specifies general requirements for pilot operated safety valves, irrespective of the fluid for which they are designed. In all cases, the operation is carried out by the fluid in the system to be protected. It is applicable to pilot operated safety valves having a valve 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 it is not applicable to applications of pilot operated safety valves.
Sicherheitseinrichtungen gegen unzulässigen Überdruck - Teil 4: Pilotgesteuerte Sicherheitsventile (ISO 4126-4:2013)
Dieser Teil der vorliegenden Norm legt allgemeine Anforderungen an pilotgesteuerte Sicherheitsventile unabhängig von dem Medium fest, für das sie ausgelegt sind. Die Funktion wird in allen Fällen durch das Medium in dem zu schützenden System ausgelöst.
Die Norm gilt für pilotgesteuerte Sicherheitsventile mit einem engsten Strömungsdurchmesser von min-destens 6 mm und für Ansprechdrücke von mindestens 0,1 bar. Temperaturgrenzen sind nicht festgelegt.
Diese Norm ist eine Produktnorm und behandelt keine Anwendungsfälle für pilotgesteuerte Sicherheitsventile.
Dispositifs de sécurité pour protection contre les pressions excessives - Partie 4: Soupapes de sûreté pilotées (ISO 4126-4:2013)
L'ISO 4126-4:2013 spécifie les exigences générales des soupapes de sûreté pilotées, quel que soit le fluide pour lequel elles sont conçues. Dans tous les cas, le fonctionnement est assuré par le fluide contenu dans le système à protéger.
Elle est applicable aux soupapes de sûreté pilotées 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 4126-4:2013 est une norme de produit et elle n'est pas applicable à la mise en ?uvre des soupapes de sûreté pilotées.
Naprave za varovanje pred visokim tlakom - 4. del: Predkrmiljeni varnostni ventili (ISO 4126-4:2013)
Ta del standarda ISO 4126 določa splošne zahteve za pilotsko upravljane varnostne ventile ne glede na tekočino, za katero so oblikovani. V vseh primerih delovanje poteka s tekočino v sistemu, ki naj se zaščiti. Uporablja se za pilotsko upravljane 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 pilotsko upravljanih varnostnih ventilov.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 4126-4:2013
01-september-2013
1DGRPHãþD
SIST EN ISO 4126-4:2004
Naprave za varovanje pred visokim tlakom - 4. del: Predkrmiljeni varnostni ventili
(ISO 4126-4:2013)
Safety devices for protection against excessive pressure - Part 4: Pilot-operated safety
valves (ISO 4126-4:2013)
Sicherheitseinrichtungen gegen unzulässigen Überdruck - Teil 4: Pilotgesteuerte
Sicherheitsventile (ISO 4126-4:2013)
Dispositifs de sécurité pour protection contre les pressions excessives - Partie 4:
Soupapes de sûreté pilotées (ISO 4126-4:2013)
Ta slovenski standard je istoveten z: EN ISO 4126-4:2013
ICS:
13.240 Varstvo pred previsokim Protection against excessive
tlakom pressure
SIST EN ISO 4126-4:2013 en,fr
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 4126-4:2013
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SIST EN ISO 4126-4:2013
EUROPEAN STANDARD
EN ISO 4126-4
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2013
ICS 13.240 Supersedes EN ISO 4126-4:2004
English Version
Safety devices for protection against excessive pressure - Part
4: Pilot-operated safety valves (ISO 4126-4:2013)
Dispositifs de sécurité pour protection contre les pressions Sicherheitseinrichtungen gegen unzulässigen Überdruck -
excessives - Partie 4: Soupapes de sûreté pilotées (ISO Teil 4: Pilotgesteuerte Sicherheitsventile (ISO 4126-4:2013)
4126-4:2013)
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 4126-4:2013: E
worldwide for CEN national Members.
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SIST EN ISO 4126-4:2013
EN ISO 4126-4:2013 (E)
Contents Page
Foreword .3
Annex ZA (informative) Relationship between this International Standard and the Essential
Requirements of EU Directive 97/23/EC (PED) .4
2
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SIST EN ISO 4126-4:2013
EN ISO 4126-4:2013 (E)
Foreword
This document (EN ISO 4126-4:2013) 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 4126-4:2004.
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 4126-4:2013 has been approved by CEN as EN ISO 4126-4:2013 without any modification.
3
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SIST EN ISO 4126-4:2013
EN ISO 4126-4:2013 (E)
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.
4
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SIST EN ISO 4126-4:2013
INTERNATIONAL ISO
STANDARD 4126-4
Second edition
2013-07-15
Safety devices for protection against
excessive pressure —
Part 4:
Pilot operated safety valves
Dispositifs de sécurité pour protection contre les pressions excessives —
Partie 4: Soupapes de sûreté pilotées
Reference number
ISO 4126-4:2013(E)
©
ISO 2013
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SIST EN ISO 4126-4:2013
ISO 4126-4:2013(E)
COPYRIGHT PROTECTED DOCUMENT
© 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
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SIST EN ISO 4126-4:2013
ISO 4126-4:2013(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and units . 5
5 Design . 5
5.1 General . 5
5.2 Valve end connections . 6
5.3 Minimum requirements for springs . 6
5.4 Materials . 7
6 Production testing . 7
6.1 Purpose . 7
6.2 General . 7
6.3 Hydrostatic testing . 7
6.4 Pneumatic testing . 8
6.5 Adjustment of set or cold differential test pressure . 8
6.6 Seat leakage test. 9
6.7 Pressure seals . 9
7 Type testing. 9
7.1 General . 9
7.2 Tests to determine operating characteristics .10
7.3 Tests to determine flow characteristics.12
7.4 Determination of the coefficient of discharge .14
7.5 Certification of coefficient of discharge .14
8 Determination of pilot operated safety valve performance .14
9 Sizing of pilot operated safety valves .14
10 Marking and sealing .14
10.1 Marking .14
10.2 Sealing of a pilot operated safety valve .15
Bibliography .16
© ISO 2013 – All rights reserved iii
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SIST EN ISO 4126-4:2013
ISO 4126-4:2013(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 4126-4 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 4126-4:2004), which has been technically
revised. It also incorporates the Technical Corrigendum ISO 4126-4:2004/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 development.
iv © ISO 2013 – All rights reserved
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SIST EN ISO 4126-4:2013
INTERNATIONAL STANDARD ISO 4126-4:2013(E)
Safety devices for protection against excessive pressure —
Part 4:
Pilot operated safety valves
1 Scope
This part of ISO 4126 specifies general requirements for pilot operated safety valves, irrespective of the
fluid for which they are designed. In all cases, the operation is carried out by the fluid in the system to
be protected.
It is applicable to pilot operated safety valves having a valve 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 it is not applicable to applications of pilot operated 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
pilot operated safety valve
self-actuated device comprising a main valve and an attached pilot
Note 1 to entry: The pilot responds to the pressure of the fluid without any other actuating energy than the fluid
itself and controls the operation of the main valve. The main valve opens when the fluid pressure that keeps it
closed is removed or reduced. The main valve re-closes when the pressure is re-applied.
Note 2 to entry: See Figure 1 for a list of main components.
3.2
main valve
parts of a pilot operated safety valve, through which the discharge capacity is achieved
3.3
flowing pilot
pilot which discharges the fluid throughout the relieving cycle of the pilot operated safety valve
© ISO 2013 – All rights reserved 1
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SIST EN ISO 4126-4:2013
ISO 4126-4:2013(E)
Key
1 equipment to be protected 9 disc (or piston)
2 main valve 10 seat
3 pilot valve 11 main valve body
4 sensing line 12 main valve inlet
5 loading/unloading line 13 main valve outlet
6 pressure chamber 14 pilot outlet
7 cover (or cap) 15 connection of the sensing line (see Note)
8 guide
NOTE The sensing line from the pilot can be either connected to the main valve inlet or connected directly
to the equipment to be protected. In cases where the sensing line is not connected to the main valve inlet,
considerations should be given to the length and to the protection from damage of the sensing line.
Figure 1 — Nomenclature of main components of a pilot operated safety valve
3.4
non-flowing pilot
pilot in which the fluid flows only during the opening and/or closing of the pilot operated safety valve
3.5
ON/OFF
action characterized by stable operation resulting in fully open or fully closed main valve position
Note 1 to entry: This is an action of the pilot operated safety valve.
2 © ISO 2013 – All rights reserved
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SIST EN ISO 4126-4:2013
ISO 4126-4:2013(E)
3.6
modulating
action characterized by a gradual opening and closing of the disc of the main valve which is a function of
the pressure, proportional but not necessarily linear
Note 1 to entry: This is an action of the pilot operated safety valve.
3.7
set pressure
predetermined pressure at which the main valve of a pilot operated safety valve under operating
conditions commences to open
Note 1 to entry: It is the gauge pressure measured at the main valve inlet at which the pressure forces tending to
lift the main valve disc for the specific service conditions are in equilibrium with the forces retaining the main
valve disc on its seat.
3.8
maximum allowable pressure
PS
maximum pressure for which the protected equipment is designed
3.9
opening sensing pressure
pressure at which the pilot commences to open in order to achieve the set pressure
3.10
overpressure
pressure increase over the set pressure, usually expressed as a percentage of the set pressure
3.11
reseating pressure
value of the inlet static pressure at which the main valve disc re-establishes contact with the seat or at
which the lift becomes zero
3.12
cold differential test pressure
inlet static pressure at which a pilot operated 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.
3.13
relieving pressure
pressure used for the sizing of a pilot operated safety valve which is greater than or equal to the set
pressure plus overpressure
3.14
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.
3.15
built-up back pressure
pressure existing at the outlet of the main valve caused by flow through the main valve and the
discharge system
3.16
superimposed back pressure
pressure existing at the outlet of the main 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.
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SIST EN ISO 4126-4:2013
ISO 4126-4:2013(E)
3.17
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.
3.18
lift
actual travel of the main valve disc away from the closed position
3.19
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 flowing capacity of the main valve, with no deduction for
any obstruction
3.20
flow diameter
diameter corresponding to the flow area
3.21
theoretical discharge capacity
calculated capacity of a theoretically perfect nozzle having a cross-sectional flow area equal to the flow
area of the main valve of a pilot operated safety valve
Note 1 to entry: It is expressed in mass or volumetric units.
3.22
coefficient of discharge
value of actual flowing capacity (from tests) divided by the theoretical flowing capacity (from calculation)
3.23
certified (discharge) capacity
portion of the measured capacity permitted to be used as a basis for the application of a pilot
operated safety valve
Note 1 to entry: It may, for example, equal the: a) measured flow rate times the de-rating factor; or b) theoretical
flow rate times the coefficient of discharge times the de-rating factor; or c) theoretical flow rate times the certified
de-rated coefficient of discharge.
3.24
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.
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SIST EN ISO 4126-4:2013
ISO 4126-4:2013(E)
4 Symbols and units
Table 1 — Symbols and their descriptions
Symbol Description Unit
2
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 —
2
q Theoretical specific discharge capacity kg/(h⋅mm )
m
2
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 the main 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 Means shall be provided to lock and/or to seal all external adjustments in such a manner so as to
prevent or reveal unauthorized adjustments of the pilot operated safety valve.
5.1.4 In the case of main valves with restricted lift, the lift restricting device shall limit the main valve
lift but shall not otherwise interfere with the operation of the main valve. The lift restricting device shall
be designed so that, if adjustable, the adjustable feature can be mechanically locked and sealed. The lift
restricting device shall be installed and sealed in accordance with the design of the manufacturer.
The valve lift shall not be restricted to a value less than 1 mm.
5.1.5 Pilot operated safety valves for toxic or flammable fluids shall have the pilot vented to a safe place.
5.1.6 The main valve shall be provided with a drain connection at the lowest point where liquid can
collect unless other provisions for draining are provided.
5.1.7 The design stress of pressure-retaining shells shall not exceed that specified in the
appropriate standards.
NOTE For example, EN 12516 or ANSI/ASME B 16.34 may be used as reference.
5.1.8 The materials for adjacent sliding surfaces such as guides and disc/disc holder/spindle shall be
selected to ensure corrosion resistance and to minimize wear and avoid galling.
5.1.9 In the case of reasonably foreseeable damage to connections between the various components,
the resulting flow areas shall be such that the pilot operated safety valve will discharge its certified
capacity at not more than 1,1 times the maximum allowable pressure.
5.1.10 When the superimposed back pressure can be higher than the inlet pressure, means shall be
provided so that the main valve does not open.
5.1.11 Easing gear shall be provided when specified or alternatively means for connecting and applying
pressure to the pilot adequate to verify that the moving parts critical to proper operation are free to move.
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SIST EN ISO 4126-4:2013
ISO 4126-4:2013(E)
5.1.12 The fitting of any additional device to a pilot and main valve combination shall not prevent the
pressurized system from being protected under any circumstances.
5.2 Valve end connections
The inlet design of valve end connections, regardless of type, shall be such that the internal area of
the external pipe or stub connection at the safety valve inlet is at least equal to that of the valve inlet
connection [see Figure 2 a)].
The outlet design of valve end connections, regardless of type, shall be such that the internal area of
the external pipe connection at the safety valve outlet is at least equal to that of the valve outlet, except
those valves with female threaded outlet connections [see Figure 2 b)].
NOTE See Clause 7 regarding type testing.
a) Inlet
b) Outlet
Key
1 main valve 3 unsatisfactory
2 satisfactory 4 required internal diameter of the pilot operated
safety valve for the valve to function properly
a
If the nominal diameter of the pipe is not equal to the nominal diameter of the valve outlet as shown, then a
suitable pipe shall be fitted during testing as specified in 7.1.4.
Figure 2 — Design of end connections
5.3 Minimum requirements for springs
Pressure setting springs, as applicable, shall be in accordance with ISO 4126-7.
6 © ISO 2013 – All rights reserved
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SIST EN ISO 4126-4:2013
ISO 4126-4:2013(E)
5.4 Materials
Only approved materials shall be used for pressure retaining shells.
NOTE For example, EN 12516 or any other national or internationally recognized standards (e.g. ASME, JIS,
etc.) may be used as reference.
These materials and their temperature limitations shall be suitable for pressure-containing function.
6 Production testing
6.1 Purpose
The purpose of these tests is to ensure that all pilot operated safety valves meet the requirements
for which they have been designed without exhibiting any form of leakage from pressure-retaining
components or joints.
6.2 General
All temporary pipes, connections and blanking devices shall be adequate to withstand the test pressure.
Any temporary welded-on attachments shall be carefully removed and the resulting weld scars shall
be ground flush with the parent material. After grinding, all such scars shall be inspected by using
magnetic particle or liquid penetrant techniques.
6.3 Hydrostatic testing
6.3.1 Application
The portion of the main valve shell exposed to the inlet pressure shall be tested to a pressure 1,5 times
the manufacturer’s stated maximum pressure for which the pilot operated safety valve is designed.
The portion of the main valve shell exposed to outlet pressure shall be te
...
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