ISO 21157:2018

INTERNATIONAL ISO
STANDARD 21157
First edition
2018-11
Ships and marine technology — Ball
valves for use in low temperature
applications — Design and testing
requirements
Navires et technologie maritime — Robinets à boisseau sphérique
destinés aux applications à basse température — Exigences de
conception et d'essai
Reference number
©
ISO 2018
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2018 – All rights reserved

Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Pressure-temperature rating . 3
5 Structure . 3
5.1 General . 3
5.1.1 Structure . 3
5.1.2 Materials . 3
5.2 Design and materials of the body. 4
5.2.1 Design . 4
5.2.2 Materials . 4
5.2.3 Manufacturing . 4
5.3 Design and materials of the extended bonnet . 5
5.3.1 Design . 5
5.3.2 Materials . 5
5.4 Design and materials of ball . 5
5.4.1 Design . 5
5.4.2 Materials . 5
5.5 Design and materials of the stem . 5
5.5.1 Design . 5
5.5.2 Materials . 5
5.6 Stem sealing . 6
5.7 Design and materials of the seat . 6
5.7.1 Design . 6
5.7.2 Materials . 6
5.8 Design and materials of bolting . 6
5.8.1 Design . 6
5.8.2 Materials . 6
5.9 Requirement of operating device and actuators . 7
5.10 Surface treatment . 7
5.11 Welding and heat treatment . 7
5.11.1 Welding . 7
5.11.2 Heat treatment. 7
5.12 Repair welding . 8
6 Test and inspection . 8
6.1 General . 8
6.2 Material test . 8
6.3 Non-destructive inspection . 8
6.3.1 General. 8
6.3.2 Radiographic testing (RT) . 8
6.3.3 Penetrant testing (PT) . 9
6.3.4 Ultrasonic testing (UT) . 9
6.3.5 Retest . 9
6.3.6 Submission of inspection results . 9
6.4 Dimension check . 9
6.5 Visual inspection .10
6.6 Heat treatment inspection .10
6.7 Operating tests .10
6.8 Pressure test .10
6.8.1 Pressure test in ambient temperature .10
6.8.2 Test procedure and method .10
6.8.3 Test of cavity pressure relief .11
6.9 Fire-resistance test (if necessary) .11
6.10 Anti-static testing.11
6.11 Cryogenic tests .11
6.11.1 General.11
6.11.2 Scope of tests .11
6.11.3 Test procedure .12
6.11.4 Submission of test result .13
7 Marking .13
Annex A (informative) Examples of ball valve construction .14
iv © ISO 2018 – All rights reserved

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
...