oSIST prEN ISO 28921-1:2021

Industrial valves - Isolating valves for low-temperature applications - Part 1: Design, manufacturing and production testing (ISO/DIS 28921-1:2021)

Industriearmaturen - Absperrventile für die Anwendung im Tieftemperaturbereich - Teil 1: Auslegung, Fertigung und Produktionsprüfung (ISO/DIS 28921-1:2021)

Dieses Dokument legt Anforderungen an die Auslegung, Maße, das Material, die Fertigung und die Fertigungsprüfung von Schiebern, Durchgangsventilen, Kugel-/Kegelventilen und Drosselventilen, die als Absperrventile und Rückschlagventile für Tieftemperaturanwendungen eingesetzt werden, fest.
Dieses Dokument behandelt Absperrventile zum Einsatz im tiefen und kryogenen Temperaturbetrieb, in welchem der geplante Tieftemperaturbereich zwischen −50 °C und −196 °C liegt.
Dieses Dokument 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 Dokuments von den Anforderungen in der Produktnorm der Ventile abweichen, sind die Anforderungen dieses Dokuments anzuwenden.
Dieses Dokument 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; 950; 1 000; 1 050; 1 200; 1 350; 1 400; 1 500; 1 600; 1 650; 1 800,
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; 38; 40; 42; 48; 54; 56; 60; 64; 66; 72,
und anwendbar auf Druckbezeichnungen:
- PN 16; 25; 40; 100; 160; 250; 400;
- Class 150; 300; 600; 800; 900; 1 500; 2 500.
ANMERKUNG Nicht alle Typen- und Größenkombinationen sind in allen Druckstufen verfügbar.
Dieses Dokument schließt die Prüfung für Sicherheits- und Regelventile aus.

Robinetterie industrielle - Robinets d'isolement pour application à basses températures - Partie 1: Conception, essais de fabrication et de production (ISO/DIS 28921-1:2021)

Industrijski ventili - Zapirni ventili za uporabo pri nizki temperaturi - 1. del: Načrtovanje, proizvodnja in preskušanje med proizvodnjo (ISO/DIS 28921-1:2021)

General Information

• Status: Not Published
• Public Enquiry End Date: 04-Jul-2021
• ICS: 23.060.01 - Valves in general
• Technical Committee: IHPV - Hydraulics and pneumatics
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 17-May-2021
• Due Date: 04-Oct-2021
• Completion Date: 04-Jun-2021
• Ref Project: prEN ISO 28921-1 - Industrial valves - Isolating valves for low-temperature applications - Part 1: Design, manufacturing and production testing (ISO/DIS 28921-1:2021)

RELATIONS

• Revised: SIST EN ISO 28921-1:2017 - Industrial valves - Isolating valves for low-temperature applications - Part 1: Design, manufacturing and production testing (ISO 28921-1:2013)
• Effective Date: 01-Jul-2021

Standards Content (sample)

SLOVENSKI STANDARD
oSIST prEN ISO 28921-1:2021
01-julij-2021

Industrijski ventili - Zapirni ventili za uporabo pri nizki temperaturi - 1. del:

Načrtovanje, proizvodnja in preskušanje med proizvodnjo (ISO/DIS 28921-1:2021)

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

manufacturing and production testing (ISO/DIS 28921-1:2021)

Industriearmaturen - Absperrventile für die Anwendung im Tieftemperaturbereich - Teil 1:

Auslegung, Fertigung und Produktionsprüfung (ISO/DIS 28921-1:2021)

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

Partie 1: Conception, essais de fabrication et de production (ISO/DIS 28921-1:2021)

Ta slovenski standard je istoveten z: prEN ISO 28921-1
ICS:
23.060.01 Ventili na splošno Valves in general
oSIST prEN ISO 28921-1:2021 en,fr,de

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

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oSIST prEN ISO 28921-1:2021
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oSIST prEN ISO 28921-1:2021
DRAFT INTERNATIONAL STANDARD
ISO/DIS 28921-1
ISO/TC 153 Secretariat: AFNOR
Voting begins on: Voting terminates on:
2021-04-13 2021-07-06
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
ICS: 23.060.01
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 28921-1:2021(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION. ISO 2021
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oSIST prEN ISO 28921-1:2021
ISO/DIS 28921-1:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

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: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
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oSIST prEN ISO 28921-1:2021
ISO/DIS 28921-1:2021(E)
Contents Page

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

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

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

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

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

4 Requirements .......................................................................................................................................................................................................... 4

4.1 Materials ....................................................................................................................................................................................................... 4

4.1.1 General...................................................................................................................................................................................... 4

4.1.2 Metallic materials ............................................................................................................................................................ 4

4.1.3 Internal non-metallic materials .......................................................................................................................... 5

4.2 Design ............................................................................................................................................................................................................. 5

4.2.1 General...................................................................................................................................................................................... 5

4.2.2 Body/bonnet wall thickness .................................................................................................................................. 5

4.2.3 Body and bonnet extension .................................................................................................................................... 5

4.2.4 Stem .........................................................................................................................................................................................10

4.2.5 Seats and seating surfaces ....................................................................................................................................10

4.2.6 Provision for internal pressure relief ..........................................................................................................10

4.2.7 Operating means ...........................................................................................................................................................11

4.2.8 Electric continuity and fire-safe design ....................................................................................................11

5 Testing ..........................................................................................................................................................................................................................11

5.1 Production testing with low-temperature test ......... ................................................................................................11

5.2 Type-testing ............................................................................................................................................................................................11

6 Sampling .....................................................................................................................................................................................................................12

6.1 Lot requirements ...............................................................................................................................................................................12

6.2 Sample size ..............................................................................................................................................................................................12

6.3 Lot acceptance ......................................................................................................................................................................................12

7 Marking, labelling and packaging ...................................................................................................................................................12

Annex A (normative) Test procedure for production testing of valves at low temperature ....................14

Annex B (informative) Low-temperature test record ......................................................................................................................23

Bibliography .............................................................................................................................................................................................................................25

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oSIST prEN ISO 28921-1:2021
ISO/DIS 28921-1:2021(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 153, Valves.

This second edition cancels and replaces the first edition ( ISO 28921-1:2013), which has been

technically revised.
The main changes compared to the previous edition are as follows:

— extension to include sizes DN 950 to 1 800, NPS 38 to 72, and pressure designations PN 400 and

Class 2 500;
— addition of a new definition 3.13 for shell;
— addition of a new definition 3.14 for drip plate;
— exclusion of safety valves and control valves;
— in 5.2, addition of type test requirement in accordance with ISO 28921-2;

— update of Annex A giving the test procedure for production testing of valves at low temperature.

A list of all parts in the ISO 28921 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 2021 – All rights reserved
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oSIST prEN ISO 28921-1:2021
ISO/DIS 28921-1:2021(E)
Introduction

The purpose of this document 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.
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oSIST prEN ISO 28921-1:2021
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oSIST prEN ISO 28921-1:2021
DRAFT INTERNATIONAL STANDARD ISO/DIS 28921-1:2021(E)
Industrial valves — Isolating valves for low-temperature
applications —
Part 1:
Design, manufacturing and production testing
1 Scope

This document specifies requirements for design, dimensions, material, fabrication and production

testing of gate, globe, ball/plug and butterfly valve design types used as isolation valves and check

valves for low-temperature applications.

This document covers isolation valves for use in low and cryogenic temperature service where the

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

This document does not apply to valves for cryogenic services, designed in accordance with ISO 21011,

used with cryogenic vessels.

Where the requirements of this document vary from those given in the valve product standards, the

requirements of this document apply.

This document 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; 950; 1 000; 1 050; 1 200; 1 350; 1 400; 1 500; 1 600;

1 650; 1 800.

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; 38; 40; 42; 48; 54; 56; 60; 64; 66; 72,
and applies to pressure designations:
— PN 16; 25; 40; 100; 160; 250; 400;
— Class 150; 300; 600; 800; 900; 1 500; 2 500.
NOTE Not all type and size combination are available in all pressure ratings.
This document excludes testing for safety valves and control valves.
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 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
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oSIST prEN ISO 28921-1:2021
ISO/DIS 28921-1:2021(E)

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

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

gas industries

ISO 15848-1:2015, Industrial valves — Measurement, test and qualification procedures for fugitive

emissions — Part 1: Classification system and qualification procedures for type testing of valves

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

ISO 28921-2, Industrial valves — Isolating valves for low-temperature applications — Part 2: Type testing

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 12516-4, Industrial valves — Shell design strength — Part 4: Calculation method for valve shells

manufactured in metallic materials other than steel
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
ASME B16.34, Valves Flanged, Threaded and Welding End
ASME B31.3, Process Piping
Boiler ASME, and Pressure Vessel Code, Section VIII
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
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.

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oSIST prEN ISO 28921-1:2021
ISO/DIS 28921-1:2021(E)
[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.

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
Note 1 to entry: 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

Note 1 to entry: 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
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oSIST prEN ISO 28921-1:2021
ISO/DIS 28921-1:2021(E)
3.13
shell

pressure containing envelope of the valve normally comprised of the body and when included in the

design a bonnet or cover and the body bonnet or body cover joint excluding sealing parts

3.14
drip plate

plate attached to the extension bonnet to prevent condensation from entering the insulation layer

3.15
obturator

movable component of the valve whose position in the fluid flow path permits, restricts or obstructs

the fluid flow
3.16
DBB valve

single valve with two seating surfaces that, in the closed position, provides a seal against pressure from

both ends of the valve with a means of venting/bleeding the cavity between seating surfaces

Note 1 to entry: This valve does not provide positive double isolation when only one side is under pressure.

3.17
DIB valve

single valve with two seating surfaces, each of which, in the closed position, provides a seal against

pressure from a single source, with a means of venting/bleeding the cavity between the seating surfaces

Note 1 to entry: This feature can be provided in one direction or in both directions: DIB-1 (both seats

bidirectional) or DIB-2 (one seat unidirectional and one seat bidirectional).
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.

4.1.2 Metallic materials
4.1.2.1 Shell
For material suitability at low temperature, use ASME B31.3 or EN 13480-2.

The material of body, bonnet, bonnet extension and cover, and other parts of the shell, shall be selected

from the following.

a) Low alloy and austenitic stainless steel materials listed in ASME B16.34 or EN 12516-1 for Class

designated valves or EN 12516-1 for PN designated valves.
b) Nickel alloy materials listed in ASME B16.34 for Class designated valves.

c) Copper alloy materials listed in EN 12516-4 for Class and PN designated valves.

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oSIST prEN ISO 28921-1:2021
ISO/DIS 28921-1:2021(E)
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, ball, plug, 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, seats 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 document 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 or EN 12516-4 for Class-designated valves and EN 12516-1 or EN 12516-2 or EN 12516-4

for PN designated valves. The pressure rating of the valve at or below service temperatures –50 °C shall

not exceed the cold working pressure 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.

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oSIST prEN ISO 28921-1:2021
ISO/DIS 28921-1:2021(E)

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.
Key
a minimum vapour column length for non-cold box application (see Table 1)
b extension for cold box application (see Table 2)
c outline of cold box enclosure
d bottom of the packing chamber
e optional drip plate
f top of stem guide or bonnet
Figure 1 — Valve with extended bonnet
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oSIST prEN ISO 28921-1:2021
ISO/DIS 28921-1:2021(E)
Table 1 — Minimum vapour column length for non-cold box extension
Valve size range Minimum vapour column length Valve size range
DN mm NPS
Minimum design temperature
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
≥ 950 To be agreed between purchaser and the manufacturer ≥ NPS 38
Table 2 — Minimum bonnet extension length for cold box applications
Valve size Minimum bonnet extension length Valve size
DN mm 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
≥ 950 To be agreed between purchaser and the manufacturer ≥ NPS 38
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 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.

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oSIST prEN ISO 28921-1:2021
ISO/DIS 28921-1:2021(E)

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
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oSIST prEN ISO 28921-1:2021
ISO/DIS 28921-1:2021(E)

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).
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 or topside of the

valve body.

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.

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oSIST prEN ISO 28921-1:2021
ISO/DIS 28921-1:2021(E)

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. Wh
...