Industrial valves - Isolating valves for low-temperature applications - Part 1: Design, manufacturing and production testing (ISO 28921-1:2013)

ISO 28921-1:2013 specifies requirements for design, dimensions, material, fabrication and production testing of isolation valves for low-temperature applications. It applies to gate, globe, check, butterfly and ball valves and can be used for other valve types used in low-temperature services.
ISO 28921-1:2013 covers isolation valves for use in cryogenic temperature service where the design low-temperature service is ?50 °C down to ? 96 °C. It covers valves with body, bonnet, bonnet extension or cover made of metallic materials.
ISO 28921-1:2013 covers valves of nominal sizes DN: 10; 15; 20; 25; 32; 40; 50; 65; 80; 100; 125; 150; 200; 250; 300; 350; 400; 450; 500; 600; 650; 700; 750; 800; 850; 900, corresponding to nominal pipe sizes NPS: 3/8; ½; ; 1; 11/4; 11/2; 2; 21/2; 3; 4; 5; 6; 8; 10; 12; 14; 16; 18; 20; 24; 26; 28; 30; 32; 34; 36.
It applies to pressure designations:
PN 16; 25; 40; 100; 160; 250;
Class 150; 300; 600; 800; 900; 1 500.

Industriearmaturen - Absperrventile für die Anwendung im Tieftemperaturbereich - Teil 1: Auslegung, Fertigung und Produktionsprüfung (ISO 28921-1:2013)

Dieser Teil der ISO 28921 legt Anforderungen an die Auslegung, Maße, das Material, die Fertigung und die Fertigungsprüfung von Absperrventilen für Tieftemperaturanwendungen fest.
Er ist auf Schieber, Durchgangsventile, Rückschlagventile, Drosselventile und Kugelventile anwendbar und kann auch für andere Ventilarten im Tieftemperaturbereich eingesetzt werden.
Dieser Teil der ISO 28921 behandelt Absperrventile zum Einsatz im kryogenen Temperaturbetrieb, in welchem der geplante Tieftemperaturbereich zwischen −50 °C und −196 °C liegt.
Dieser Teil der ISO 28921 gilt nicht für Ventile für den kryogenen Betrieb, die in Übereinstimmung mit ISO 21011 für den Einsatz mit Kryo Behältern ausgelegt sind.
In Fällen, in denen die Anforderungen dieses Teils der ISO 28921 von den Anforderungen in der Produktnorm der Ventile abweichen, sind die Anforderungen dieses Teils der ISO 28921 anzuwenden.
Dieser Teil der ISO 28921 behandelt Ventile mit einem Ventilgehäuse, einem Ventiloberteil, einer Verlängerung des Oberteils oder einem Deckel aus metallischen Werkstoffen.
Es werden Ventile der folgenden Nennweiten DN abgedeckt: 10; 15; 20; 25; 32; 40; 50; 65; 80; 100; 125; 150; 200; 250; 300; 350; 400; 450; 500; 600; 650; 700; 750; 800; 850; 900,
entsprechend den NPS: 3/8; 1/2; 3/4; 1; 11/4; 11/2; 2; 21/2; 3; 4; 5; 6; 8; 10; 12; 14; 16; 18; 20; 24; 26; 28; 30; 32; 34; 36,
und anwendbar auf Druckbezeichnungen:
   PN 16; 25; 40; 100; 160; 250.
   Class 150; 300; 600; 800; 900; 1 500.
ANMERKUNG   PN 250 und Class 1 500 in Größen DN > 100 und NPS > 4 werden nicht von diesem Teil der ISO 28921 abgedeckt.

Robinetterie industrielle - Robinets d'isolement pour application à basses températures - Partie 1: Conception, essais de fabrication et de production (ISO 28921-1:2013)

L'ISO 28921-1:2013 spécifie les exigences relatives à la conception, aux dimensions, aux matériaux, à la fabrication et aux essais de production des robinets d'isolement pour application à basses températures.
Elle s'applique aux robinets-vannes, aux robinets à soupape, aux clapets de non-retour, aux robinets à papillon et aux robinets à tournant sphérique et peut être utilisée pour d'autres types d'appareils de robinetterie destinés à un usage à basses températures.
L'ISO 28921-1:2013 traite des robinets d'isolement destinés à un usage à basses températures pour lesquels la température de calcul est comprise entre -50 °C et -196 °C.
Elle traite des appareils de robinetterie dont le corps, le chapeau, l'extension du chapeau ou le couvercle sont en matériaux métalliques.
L'ISO 28921-1:2013 couvre les appareils de robinetterie de diamètre nominal DN: 10; 15; 20; 25; 32; 40; 50; 65; 80; 100; 125; 150; 200; 250; 300; 350; 400; 450; 500; 600; 650; 700; 750; 800; 850; 900, correspondant à des dimensions nominales de tubes NPS: 3/8; 1/2; 3/4; 1; 1 1/4; 1 1/2; 2; 2 1/2; 3; 4; 5; 6; 8; 10; 12; 14; 16; 18; 20; 24; 26; 28; 30; 32; 34; 36.
Elle s'applique aux désignations de pression:
PN 16; 25; 40; 100; 160; 250;
Class 150; 300; 600; 800; 900; 1 500.

Industrijski ventili - Zapirni ventili za uporabo pri nizki temperaturi - 1. del: Načrtovanje, proizvodnja in preskušanje med proizvodnjo (ISO 28921-1:2013)

ISO 28921-1:2013 določa zahteve glede zasnove, dimenzij, materiala, izdelave in proizvodnega preskušanja izolacijskih ventilov za uporabo pri nizkih temperaturah. Uporablja se za zasune, zapiralne ventile, protipovratne ventile, zaporne lopute ter krogelne ventile in se lahko uporablja za druge vrste ventilov, ki se uporabljajo pri nizkih temperaturah.
ISO 28921-1:2013 zajema izolacijske ventile za uporabo pri kriogenih temperaturah, pri čemer je predviden razpon nizke temperature od ?50 °C do ? 96 °C. To zajema ventile z ohišjem, pokrovom, podaljškom pokrova ali plaščem iz kovinskih materialov.
ISO 28921-1:2013 zajema ventile nazivnih velikosti DN: 10; 15; 20; 25; 32; 40; 50; 65; 80; 100; 125; 150; 200; 250; 300; 350; 400; 450; 500; 600; 650; 700; 750; 800; 850; 900, ki ustrezajo nazivnim velikostim cevi NPS: 3/8; ½; 1; 11/4; 11/2; 2; 21/2; 3; 4; 5; 6; 8; 10; 12; 14; 16; 18; 20; 24; 26; 28; 30; 32; 34; 36.
Uporablja se za označbe tlaka:
PN 16; 25; 40; 100; 160; 250;
Class 150; 300; 600; 800; 900; 1 500.

General Information

Status
Withdrawn
Public Enquiry End Date
07-Aug-2016
Publication Date
30-Mar-2017
Withdrawal Date
06-Jun-2022
Current Stage
9900 - Withdrawal (Adopted Project)
Start Date
02-Jun-2022
Due Date
25-Jun-2022
Completion Date
07-Jun-2022

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Standards Content (sample)

SLOVENSKI STANDARD
SIST EN ISO 28921-1:2017
01-maj-2017
1DGRPHãþD
SIST EN 12567:2001

,QGXVWULMVNLYHQWLOL=DSLUQLYHQWLOL]DXSRUDERSULQL]NLWHPSHUDWXULGHO

1DþUWRYDQMHSURL]YRGQMDLQSUHVNXãDQMHPHGSURL]YRGQMR ,62

Industrial valves - Isolating valves for low-temperature applications - Part 1: Design,

manufacturing and production testing (ISO 28921-1:2013)

Robinetterie industrielle - Robinets d'isolement pour application à basses températures -

Partie 1: Conception, essais de fabrication et de production (ISO 28921-1:2013)
Ta slovenski standard je istoveten z: EN ISO 28921-1:2017
ICS:
23.060.01 Ventili na splošno Valves in general
SIST EN ISO 28921-1:2017 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 28921-1:2017
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SIST EN ISO 28921-1:2017
EN ISO 28921-1
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2017
EUROPÄISCHE NORM
ICS 23.060.01 Supersedes EN 12567:2000
English Version
Industrial valves - Isolating valves for low-temperature
applications - Part 1: Design, manufacturing and
production testing (ISO 28921-1:2013)

Robinetterie industrielle - Robinets d'isolement pour Industriearmaturen - Absperrventile für die

application à basses températures - Partie 1: Anwendung im Niedertemperaturbereich - Teil 1:

Conception, essais de fabrication et de production (ISO Auslegung, Fertigung, Produktionsprüfung (ISO 28921-

28921-1:2013) 1:2013)
This European Standard was approved by CEN on 10 January 2017.

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: Avenue Marnix 17, B-1000 Brussels

© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 28921-1:2017 E

worldwide for CEN national Members.
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SIST EN ISO 28921-1:2017
EN ISO 28921-1:2017 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 28921-1:2017
EN ISO 28921-1:2017 (E)
European foreword

The text of ISO 28921-1:2013 has been prepared by Technical Committee ISO/TC 153 “Valves” of the

International Organization for Standardization (ISO) and has been taken over as EN ISO 28921-1:2017

by 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 August 2017, and conflicting national standards shall

be withdrawn at the latest by August 2017.

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.
EN ISO 28921-1 and EN ISO 28921-2 supersede EN 12567:2000.

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 28921-1:2013 has been approved by CEN as EN ISO 28921-1:2017 without any

modification.
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SIST EN ISO 28921-1:2017
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SIST EN ISO 28921-1:2017
INTERNATIONAL ISO
STANDARD 28921-1
First edition
2013-05-01
Industrial valves — Isolating valves for
low-temperature applications —
Part 1:
Design, manufacturing and
production testing
Robinetterie industrielle — Robinets d’isolement pour application à
basses températures —
Partie 1: Conception, essais de fabrication et de production
Reference number
ISO 28921-1:2013(E)
ISO 2013
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SIST EN ISO 28921-1:2017
ISO 28921-1:2013(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 28921-1:2017
ISO 28921-1:2013(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Requirements .......................................................................................................................................................................................................... 3

4.1 Materials ....................................................................................................................................................................................................... 3

4.2 Design ............................................................................................................................................................................................................. 4

5 Testing ..........................................................................................................................................................................................................................10

5.1 Production testing with low-temperature test ......... ................................................................................................10

6 Sampling .....................................................................................................................................................................................................................10

6.1 Lot requirements ...............................................................................................................................................................................10

6.2 Sample size ..............................................................................................................................................................................................11

6.3 Lot acceptance ......................................................................................................................................................................................11

7 Marking, labelling and packaging ...................................................................................................................................................11

Annex A (normative) Test procedure for production testing of valves at low temperature ....................13

Annex B (informative) Low-temperature test record ......................................................................................................................21

Bibliography .............................................................................................................................................................................................................................23

© ISO 2013 – All rights reserved iii
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SIST EN ISO 28921-1:2017
ISO 28921-1:2013(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 28921-1 was prepared by Technical Committee ISO/TC 153, Valves, Subcommittee SC 1, Design,

manufacture, marking and testing.

ISO 28921 consists of the following parts, under the general title Industrial valves — Isolating valves for

low-temperature applications:
— Part 1: Design, manufacturing and production testing
— Part 2: Type testing
iv © ISO 2013 – All rights reserved
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SIST EN ISO 28921-1:2017
ISO 28921-1:2013(E)
Introduction

The purpose of this part of ISO 28921 is the establishment of basic requirements and practices for design,

fabrication, material selection and production testing of valves used in low-temperature services. The

intention is to provide requirements for design, material selection and valve preparation for valves to be

used in low-temperature service.
© ISO 2013 – All rights reserved v
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SIST EN ISO 28921-1:2017
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SIST EN ISO 28921-1:2017
INTERNATIONAL STANDARD ISO 28921-1:2013(E)
Industrial valves — Isolating valves for low-temperature
applications —
Part 1:
Design, manufacturing and production testing
1 Scope

This part of ISO 28921 specifies requirements for design, dimensions, material, fabrication and

production testing of isolation valves for low-temperature applications.

It applies to gate, globe, check, butterfly and ball valves and can be used for other valve types used in

low-temperature services.

This part of ISO 28921 covers isolation valves for use in cryogenic temperature service where the design

low-temperature service is –50 °C down to –196 °C.

This part of ISO 28921 does not apply to valves for cryogenic services, designed in accordance with

ISO 21011, used with cryogenic vessels.

Where the requirements of this part of ISO 28921 vary from those given in the valve product standards,

the requirements of this part of ISO 28921 apply.

This part of ISO 28921 covers valves with body, bonnet, bonnet extension or cover made of metallic materials.

It covers valves of nominal sizes DN: 10; 15; 20; 25; 32; 40; 50; 65; 80; 100; 125; 150; 200; 250; 300; 350;

400; 450; 500; 600; 650; 700; 750; 800; 850; 900,

corresponding to nominal pipe sizes NPS: 3/8; 1/2; 3/4; 1; 11/4; 11/2; 2; 21/2; 3; 4; 5; 6; 8; 10; 12; 14; 16;

18; 20; 24; 26; 28; 30; 32; 34; 36,
and applies to pressure designations:
— PN 16; 25; 40; 100; 160; 250.
— Class 150; 300; 600; 800; 900; 1 500.

NOTE PN 250 and Class 1 500 in sizes DN > 100 and NPS > 4 are not covered in this part of ISO 28921.

2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable to its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 5208, Industrial valves — Pressure testing of metallic valves
ISO 5209, General purpose industrial valves — Marking

ISO 10434, Bolted bonnet steel gate valves for the petroleum, petrochemical and allied industries

ISO 10497, Testing of valves — Fire type-testing requirements
ISO 10631, Metallic butterfly valves for general purposes

ISO 14313, Petroleum and natural gas industries — Pipeline transportation systems — Pipeline valves

© ISO 2013 – All rights reserved 1
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SIST EN ISO 28921-1:2017
ISO 28921-1:2013(E)

ISO 15761, Steel gate, globe and check valves for sizes DN 100 and smaller, for the petroleum and natural

gas industries
ISO 17292, Metal ball valves for petroleum, petrochemical and allied industries

EN 12516-1, Industrial valves — Shell design strength — Part 1: Tabulation method for steel valve shells

EN 12516-2, Industrial valves — Shell design strength — Part 2: Calculation method for steel valve shells

EN 12516-3, Valves — Shell design strength — Part 3: Experimental method
EN 1515-1, Flanges and their joints — Bolting — Part 1: Selection of bolting
EN 13480-2, Metallic industrial piping – Part 2: Materials

API 607, Fire Test for Quarter-turn Valves and Valves Equipped with Nonmetallic Seats

API 6FA, Specification for Fire Test for Valves
ANSI/ASME B16.34, Valves Flanged, Threaded and Welding End
ASME B31.3, Process Piping
ASME, ASME Boiler and Pressure Vessel Code, Section VIII
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
nominal size

alphanumeric designation of size for components of a pipework system, which is used for reference

purposes, comprising the letters DN followed by a dimensionless whole number which is indirectly

related to the physical size, in millimetres, of the bore or outside diameter of the end connections

[SOURCE: ISO 6708:1995, definition 2.1]
3.2
nominal pressure

numerical designation relating to pressure that is a convenient rounded number for reference purposes,

and which comprises the letters PN followed by the appropriate reference number

Note 1 to entry: It is intended that all equipment of the same nominal size (DN) designated by the same PN number

shall have compatible mating dimensions.

Note 2 to entry: The maximum allowable pressure depends on materials, design and working temperature, and is

to be selected from the tables of pressure/temperature ratings given in the appropriate standards.

[SOURCE: ISO 7268:1983, Clause 2, modified.]
3.3
NPS

alphanumeric designation of size for components of a pipework system, which is used for reference

purposes, and which comprises the letters NPS followed by a dimensionless number indirectly related

to the physical size of the bore or outside diameter of the end connections

Note 1 to entry: The number following the letters NPS does not represent a measurable value and is not intended

to be used for calculation purposes except where specified in the relevant standard.

2 © ISO 2013 – All rights reserved
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SIST EN ISO 28921-1:2017
ISO 28921-1:2013(E)
3.4
Class

alphanumeric designation used for reference purposes related to a combination of mechanical and

dimensional characteristics of a component of a pipework system, which comprises the word “Class”

followed by a dimensionless whole number

Note 1 to entry: The number following the word Class does not represent a measurable value and is not intended

to be used for calculation purposes except where specified in the relevant standard.

3.5
cold box

enclosure that insulates equipment from the environment without the need for insulation of each

individual component inside the enclosure
3.6
valve body or bonnet extension

extended valve body or bonnet extension that locates the operating mechanism and packing away from

the cold media in the valve

Note 1 to entry: The body/bonnet extension allows the formation of a vapour barrier between the liquefied gas

in the valve and the packing.
3.7
vapour column

portion of body/bonnet extension that allows for the formation of an insulating column of vapour

3.8
vapour column length for non-cold box application
distance between the bottom of the packing box and the top of the
lower stem guide bushing or the beginning of the bonnet extension
See Figure 1.
3.9
length of bonnet extension for cold box applications

length measured from the centre-line of the valve flow passage up to the bottom of the packing chamber

See Figure 1.
3.10
cold working pressure
CWP

maximum fluid pressure assigned to a valve for operation at a fluid temperature of –20 °C to 38 °C

3.11
cryogenics
science of materials at low temperature
3.12
test gas
minimum 97 % pure helium or nitrogen mixed with 10 % helium
4 Requirements
4.1 Materials
4.1.1 General

Materials in contact with cold process fluid or exposed to low temperatures shall be suitable for use at

the minimum design temperature specified by the purchase order. Galling, friction heating, galvanic

corrosion and material compatibility with the fluid shall also be considered in the selection of materials.

© ISO 2013 – All rights reserved 3
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SIST EN ISO 28921-1:2017
ISO 28921-1:2013(E)
4.1.2 Metallic materials
4.1.2.1 Pressure-retaining boundary
For material suitability at low temperature, use ASME B31-3 or EN 13480-2.

Body, bonnet, bonnet extension and cover, and other parts of the pressure retaining boundary, shall be

selected from materials listed in ASME B16-34 or EN 12516-1 for Class-designated valves or EN 12516-1

for PN designated valves.
4.1.2.2 Bolting

Unless otherwise specified by the purchaser, bolting for assembling shell pressure-retaining components

shall be selected from materials listed in ASME B16-34 for Class-designated valves or EN 1515-1 for PN-

designated valves.

If low-strength bolting, such as non-strain hardened austenitic stainless steel, for example ISO 3506-1

grade A1-50 and A4-50 or ASTM A320 and ASTM A193 grade B8 Class 1 is being used, the design shall

comply with ASME Boiler and Pressure Vessel Code, Section VIII, Division 1 or 2.
4.1.2.3 Internal metallic parts

Internal metallic parts, e.g. stem, wedge, disc, seats, back seat and guide bushings, shall be made of

materials suitable for use at the entire design temperature range.
4.1.3 Internal non-metallic materials

Valve parts, e.g. packing, gasket, seatings and other non-metallic valve parts exposed to low temperature,

shall be capable of functioning at the entire design temperature range.
4.2 Design
4.2.1 General

Unless otherwise specified in the purchase order, valves shall have a bonnet extension that protects

the stem packing and valve operating mechanism from the low-temperature fluid that could otherwise

damage or impair the function of these items.

This part of ISO 28921 shall be applied in conjunction with the specific requirements of a valve product

standard, such as ISO 10434, ISO 10631, ISO 14313, ISO 15761 and ISO 17292 or other recognized

standards, such as API, ASME or EN, based on an agreement between the purchaser and the manufacturer.

4.2.2 Body/bonnet wall thickness

The minimum valve body and bonnet wall thickness shall meet the requirements of ASME B16-34 or

EN 12516-1 for Class-designated valves and EN 12516-1, EN 12516-2 or EN 12516-3 for PN designated valves.

The pressure rating of the valve at or below service temperatures –50 °C shall not exceed the pressure

rating at room temperature for the applicable valve body material and appropriate Class or PN designation.

4.2.3 Body and bonnet extension

4.2.3.1 The length of the extension shall be sufficient to maintain the stem packing at a temperature

high enough to permit operation within the temperature range of the packing material.

4.2.3.2 The minimum vapour column length or bonnet extension shall be in accordance with Table 1 or

Table 2 and Figure 1, unless otherwise specified in the purchase order.
4 © ISO 2013 – All rights reserved
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SIST EN ISO 28921-1:2017
ISO 28921-1:2013(E)
Minimum vapour column length for non-cold box application (see Table 1).
Extension for cold box application (see Table 2).
Outline of cold box enclosure.
Bottom of the packing chamber.
Optional drip plate.
Top of stem guide or bonnet.
Figure 1 — Valve with extended bonnet
© ISO 2013 – All rights reserved 5
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SIST EN ISO 28921-1:2017
ISO 28921-1:2013(E)
Table 1 — Minimum vapour column length for non-cold box extension
Minimum vapour column length
Minimum design temperature
Valve size range Valve size range
DN NPS
minimum maximum minimum maximum
–196 –110 –109 –51
DN ≤ 25 200 100 NPS ≤ 1
32 ≤ DN ≤ 65 250 125 1 ¼ ≤ NPS ≤ 2 ½
80 ≤ DN ≤ 125 300 150 3 ≤ NPS ≤ 5
150 ≤ DN ≤ 200 350 175 6 ≤ NPS ≤ 8
250 ≤ DN ≤ 300 400 200 10 ≤ NPS ≤ 12
350 ≤ DN ≤ 400 450 250 14 ≤ NPS ≤ 16
450 ≤ DN ≤ 650 500 300 18 ≤ NPS ≤ 26
700 ≤ DN ≤ 850 600 400 28 ≤ NPS ≤ 34
DN 900 700 500 NPS 36
Table 2 — Minimum bonnet extension length for cold box applications
Minimum bonnet extension length
Valve size Valve size
DN NPS
Rising stem valves Quarter-turn valves
DN ≤ 25 450 400 NPS ≤ 1
32 ≤ DN ≤ 65 550 500 1 ¼ ≤ NPS ≤ 2 ½
80 ≤ DN ≤ 125 650 600 3 ≤ NPS ≤ 5
150 760 610 6
200 865 660 8
250 1 120 710 10
300 1 150 810 12
350 1 200 850 14
400 1 300 850 16
450 1 400 900 18
500 1 500 950 20
600 1 600 1 000 24
650 1 700 1 050 26
700 1 800 1 100 28
750 1 900 1 150 30
800 2 000 1 200 32
850 2 100 1 250 34
900 2 200 1 300 36
For globe valves, bonnet extension is shown up to DN 300 – NPS 12 only.

4.2.3.3 In case of a bonnet extension made of material having lower pressure/temperature rating than

the body, then the extension thickness shall be increased proportionally to meet the pressure/temperature

6 © ISO 2013 – All rights reserved
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SIST EN ISO 28921-1:2017
ISO 28921-1:2013(E)

rating of the body at all applicable temperatures. The minimum wall thickness shall be in accordance with

ASME B16-34 for Class-designated valves or EN 12516 for PN designated valves.

4.2.3.4 Bonnet extension tube thickness shall take into account pressure stresses as well as operating

torque, stem thrust and bending stresses induced by operating devices, such as handles, gears or actuators.

4.2.3.5 Stem to extended bonnet clearance should be minimized to reduce convective heat loss except

there shall be sufficient clearance to avoid interference during operation.

4.2.3.6 Valves specified to be in gas service shall be capable of operation with the extended bonnet in

any position, unless otherwise limited by the manufacturer.

4.2.3.7 Valves specified to be in liquid service, other than cold box applications, shall be capable of

operation with the extended bonnet at or above 45° above the horizontal position (see Figure 2).

Figure 2 — Recommended bonnet orientation for non-cold box installation

4.2.3.8 Valves specified to be in cold box applications, equipped with extended bonnet, for applications

with liquids, shall be capable of operating with the stem oriented 15° to 90° above the horizontal plane

(see Figure 3).
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SIST EN ISO 28921-1:2017
ISO 28921-1:2013(E)
Figure 3 — Recommended bonnet orientation for cold box installation
4.2.3.9 A stem guide shall be applied at the lower end of the extended bonnet.

Where necessary, an additional guide may be provided to the upper end of the extension. It shall be

located below the packing and designed so as not to interfere or otherwise damage the stem or the

packing during normal valve operation.
The guide can be separate or integral with the bonnet extension.

4.2.3.10 If specified on the purchase order, the extension shall be provided with an insulation collar/drip

plate. The collar/drip plate may be welded to the bonnet extension or of the clamp-on design. The clamp-

on type shall have the bolting on the upper side to enable easy adjustment. Any gap between the bonnet

and the collar/drip plate shall be sealed to avoid condensation entering into the insulated area.

4.2.3.11 The extended bonnet may be cast, forged or fabricated. Fabricated extensions shall use full

penetration welding except for valves using pipe extension DN 50 (NPS 2) or smaller, where partial

penetration V-groove welding, fillet type welding or full-strength threaded joint with seal weld may be

used. When the bonnet extension is made to a tubular specification, the material shall be seamless. The

requirements of ASME B16-34 or EN 12516 shall be met for welds to body/bonnets parts.

8 © ISO 2013 – All rights reserved
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SIST EN ISO 28921-1:2017
ISO 28921-1:2013(E)
4.2.4 Stem

4.2.4.1 Gate and globe valve stems shall have a diameter to length ratio that precludes buckling while

under compressive loading, required to fully seat the valve.

4.2.4.2 Backseats, when utilized, may be at the bottom or at the top of the body/bonnet extension.

Backseats at the bottom of the extension may increase the risk of pressure build-up in the body/bonnet

extension cavity if the valve is backseated and allowed to warm to ambient temperatures. In all cases, the

valve manufacturer shall provide a means of protection against cavity over-pressurization.

4.2.4.3 The stem shall be sized in such a way that it is able to transfer the required torque and thrust

to the valve and fully seat and unseat the closing element against pressure. Consideration shall be given

to any additional stresses resulting from the operational loads. During the stem calculations, the highest

valve rated temperature shall be used to establish the allowable material stress.

4.2.4.4 The stem shall be of one-piece construction and it shall be designed so that the stem seal

retaining fasteners alone do not retain the stem.
4.2.5 Seats and seating surfaces

Metallic seating surfaces in metal seated valves shall have edges equipped with a radius or chamfer as

necessary to prevent galling or other damage during operation.
4.2.6 Provision for internal pressure relief

4.2.6.1 Double seated valves shall be designed to prevent the build-up of body cavity pressure due

to thermal expansion or evaporation of trapped liquid in excess of 1,33 times the valve rated pressure.

Valves with backseat primary stem seal or stem guide at the bottom of the extension shall be designed to

relieve excessive pressure in the bonnet when warmed up to ambient temperature.
4.2.6.2 Unless otherwise specified, pressure relief shall function as follows:

— for upstream sealing valves, relief shall be to the downstream side of the closing member;

— for downstream sealing valves, relief shall be to the upstream side of the closing member.

For gate valves, pressure relief shall be achieved by the use of a relief hole, located so as to relief excess

cavity pressure to the upstream side of the valve when the valve is closed.

Where valve size permits, the pressure relieving hole shall be a minimum of 3 mm in diameter and

visible through the valve end-connection when the valve is closed. Where valve size does not permit a

3 mm hole, a smaller hole dia
...

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