ISO 31657-4:2025

International
Standard
ISO 31657-4
First edition
Plain bearings — Hydrodynamic
2025-10
plain journal bearings under
steady-state conditions —
Part 4:
Permissible operational parameters
for calculation of multi-lobed and
tilting pad journal bearings
Paliers lisses — Paliers lisses hydrodynamiques radiaux
fonctionnant en régime stabilisé —
Partie 4: Paramètres opérationnels admissibles du calcul pour les
paliers radiaux multilobés et à patins oscillants
Reference number
© ISO 2025
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
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Operational guide values for start-up and run-down . 1
5 Operational guide values for avoiding thermal and mechanical overloading . 4
6 Operational guide values for the bearing clearance . 5
Bibliography . 6

iii
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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 123, Plain bearings, Subcommittee SC 8,
Calculation methods for plain bearings and their applications.
This first edition of ISO 31657-4 cancels and replaces ISO/TS 31657-4:2020, which has been technically
revised.
The main changes are as follows:
— conversion from a technical specification to a full International Standard;
— correction of typographical errors.
A list of all parts in the ISO 31657 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
International Standard ISO 31657-4:2025(en)
Plain bearings — Hydrodynamic plain journal bearings under
steady-state conditions —
Part 4:
Permissible operational parameters for calculation of multi-
lobed and tilting pad journal bearings
1 Scope
This document establishes the permissible operational parameters in terms of guide values for the
calculation of selected multi-lobed and tilting-pad journal bearings.
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 31657-1:2025, Plain bearings — Hydrodynamic plain journal bearings under steady-state conditions — Part
1: Calculation of multi-lobed and tilting pad journal bearings
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Operational guide values for start-up and run-down
In order to attain a sufficient operational safety of multi-lobed and tilting-pad journal bearings by the
calculation according to ISO 31657-1, the operational characteristic value h shall be significantly above
min
the permissible operating parameter h , and the permissible operating parameters T and p shall not
lim,tr lim lim
be exceeded by the calculated operational characteristic values T and p .
max max
The guide values represent geometrically and technologically founded operational limiting values in the
tribological system of plain bearings.
They are empirical values that enable sufficient operational safety even in the event of smaller disturbing
influences (see ISO 31657-1). The empirical values indicated can be modified for special application areas.
The symbols in this document shall be in accordance with ISO 31657-1:2025, Table 1. Calculation examples
are given in ISO 31657-1:2025, Annex A. Equivalent calculation procedures exist that enable operating
conditions to be estimated and checked against acceptable conditions. Another calculation procedure is
equally admissible.
...