ISO 7902-3:2026

International
Standard
ISO 7902-3
Third edition
Hydrodynamic plain journal
2026-05
bearings under steady-state
conditions — Circular cylindrical
bearings —
Part 3:
Permissible operational parameters
Paliers lisses hydrodynamiques radiaux fonctionnant en régime
stabilisé — Paliers circulaires cylindriques —
Partie 3: Paramètres opérationnels admissibles
Reference number
© ISO 2026
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
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and units. 1
5 Operational parameters to avoid wear . 2
5.1 Minimum permissible lubrication film thickness .2
5.2 Effective waviness and maximum permissible effective waviness .2
6 Operational parameters to avoid excessive mechanical loading . 6
7 Operational parameters to avoid excessive thermal loading . 7
8 Operational parameters for the bearing clearance . 8
Bibliography . 9

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 document 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 third edition cancels and replaces the second edition (ISO 7902-3:2020), of which it constitutes a minor
revision.
The changes are as follows:
— a note on equivalent calculation procedures has been added to the introduction.
A list of all parts in the ISO 7902 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
Introduction
In order to attain sufficient operational reliability of circular cylindrical plain journal bearings when
calculated in accordance with ISO 7902-1, it is essential that the calculated operational parameters h , T
min B
or T and p do not lie above or below the permissible operational parameters h , T and p . The
ex lim lim
lim
permissible parameters represent geometrically and technologically dependent operational limits within
the plain bearing tribological system. They are empirical values which still enable sufficient operational
reliability even for minor influences (see ISO 7902-1).
NOTE Equivalent calculation procedures exist that enable operating conditions to be estimated and checked
against acceptable conditions. Another calculation procedure is equally admissible.

v
International Standard ISO 7902-3:2026(en)
Hydrodynamic plain journal bearings under steady-state
conditions — Circular cylindrical bearings —
Part 3:
Permissible operational parameters
1 Scope
This document specifies empirical permissible values for h , T and p .
lim lim
lim
The empirical values stated can be modified for certain applications, for example if information supplied by
the manufacturer is to be taken into account. The descriptions of the symbols and calculation examples are
given in ISO 7902-1.
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 7902-1:2026, Hydrodynamic plain journal bearings under steady-state conditions — Circular cylindrical
bearings — Part 1: Calculation procedure
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 Symbols and units
Symbols and units are defined in Table 1. ISO 7902-1:2026, Table 1 shall be referenced to identify the meaning
of symbols not listed in Table 1.
Table 1 — Symbols and their designations
Symbol Designation Unit
B Nominal bearing width m
C Nominal bearing clearance m
D Nominal bearing diameter (inside diameter) m
E Dimensionless modulus of elasticity 1
G Dimensionless shear modulus 1
h Waviness of sliding surface (from Figure 3) m
wav
h Effective waviness of sliding surface m
wav,eff
TTabablele 1 1 ((ccoonnttiinnueuedd))
Symbol Designation Unit
h Maximum permissible effective waviness m
wav,eff,lim
h Maximum permissible waviness m
wav,lim
i Number of waves 1
l Length of lubrication groove m
G
l Length of lubricant pocket m
P
L Length of bearing housing m
H
−1
N Rotational frequency of the bearing force s
F
Q Lubricant flow rate at the inlet to clearance gap m /s
Q Lubricant flow rate at the outlet to clearance gap m /s
Rz Average peak-to-valley height of bearing sliding surface m
B
Rz Average peak-to-valley height of shaft mating surface m
J
y Amount of deflection m
γ Angle of misalignment of the shaft rad
Period of waviness °
ϕ
wav
5 Operational parameters to avoid wear
5.1 Minimum permissible lubrication film thickness
The aim of keeping above the minimum permissible lubrication film thickness h is to retain complete
lim
lubrication of the plain bearing in order to attain least possible wear and low susceptibility to faults. The
lubricant should be free of contaminating particles, otherwise increased wear, scoring and local overheating
can result, thus impairing correct functioning of the plain bearing. If necessary, appropriate filtering of the
lubricant should be provided for.
The minimum permissible lubrication film thickness h , as a characteristic parameter for the transition to
lim
...