ISO 7902-1:2020

INTERNATIONAL ISO
STANDARD 7902-1
Third edition
2020-06
Hydrodynamic plain journal bearings
under steady-state conditions —
Circular cylindrical bearings —
Part 1:
Calculation procedure
Paliers lisses hydrodynamiques radiaux fonctionnant en régime
stabilisé — Paliers circulaires cylindriques —
Partie 1: Méthode de calcul
Reference number
©
ISO 2020
© ISO 2020
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 2020 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and units . 1
5 Basis of calculation, assumptions, and preconditions . 5
5.1 Reynolds equation . 5
5.2 Assumptions and preconditions . 5
5.3 Boundary conditions . 5
5.4 Basis of calculation . 6
5.5 Permissible operational parameters . 6
6 Calculation procedure . 6
6.1 General . 6
6.2 Freedom from wear . 6
6.3 The limits of mechanical loading. 7
6.4 The limits of thermal loading . 7
6.5 Influencing factors . 7
6.6 Reynolds number . 7
6.7 Calculation factors . 7
7 Definition of symbols . 9
7.1 Load-carrying capacity . 9
7.2 Frictional power loss . 9
7.3 Lubricant flow rate .10
7.3.1 General.10
7.3.2 Lubricant feed elements .10
7.3.3 Lubrication grooves .10
7.3.4 Lubrication pockets .10
7.3.5 Lubricant flow rate .11
7.4 Heat balance .11
7.4.1 General.11
7.4.2 Heat dissipation by convection .12
7.4.3 Heat dissipation via the lubricant .12
7.5 Minimum lubricant film thickness and specific bearing load .13
7.6 Operational conditions.14
7.7 Further influencing factors .14
Annex A (informative) Calculation examples .17
Bibliography .32
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 123, Plain bearings, Subcommittee SC 8,
Calculation methods for plain bearings and their applications.
This third edition cancels and replaces the second edition (ISO 7902-1:2013), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— subclause titles have been added;
— symbols have been corrected and added in Table 1;
— calculation values in Annex A have been corrected;
— adjustments have been made to ISO/IEC Directives, Part 2:2018;
— typographical errors have been corrected.
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 © ISO 2020 – All rights reserved

INTERNATIONAL STANDARD ISO 7902-1:2020(E)
Hydrodynamic plain journal bearings under steady-state
conditions — Circular cylindrical bearings —
Part 1:
Calculation procedure
1 Scope
This document specifies a calculation procedure for oil-lubricated hydrodynamic plain bearings, with
complete separation of the shaft and bearing sliding surfaces by a film of lubricant, used for designing
plain bearings that are reliable in operation.
It deals with circular cylindrical bearings having angular spans, Ω, of 360°, 180°, 150°, 120°, and 90°,
the arc segment being loaded centrally. Their clearance geometry is constant except for negligible
deformations resulting from lubricant film pressure and temperature.
The calculation procedure serves to provide dimensions and optimize plain bearings in turbines,
generators, electric motors, gear units, rolling mills, pumps, and other machines. It is limited to steady-
state operation, i.e. under continuously driven operating conditions, with the magnitude and direction
of loading as well as the angular speeds of all rotating parts constant. It can also be applied if a full
plain bearing is subjected to a constant force rotating at any speed. Dynamic loadings (i.e. those whose
magnitude and direction vary with time), such as those that can result from vibration effects and
instabilities of rapid-running rotors, are not taken into account.
NOTE Equivalent calculation procedures exist that enable operating conditions to be estimated and checked
against acceptable conditions. The use of them is equally admissible.
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 7902-2, Hydrodynamic plain journal bearings under steady-state conditions — Circular cylindrical
bearings — Part 2: Functions used in the calculation procedure
ISO 7902-3, Hydrodynamic plain journal bearings under steady-state conditions — Circular cylindrical
bearings — Part 3: Permissible operational parameters
3 Terms and definitions
No terms and definitions are listed in this document.
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/
4 Symbols and units
Symbols and units are defined in Figure 1 and Table 1.
Figure 1 — Illustration of symbols
Table 1 — Symbols and their designations
Symbol Designation Unit
A Area of heat-emitting surface (bearing housing) m
b Width of lubrication groove m
G
b Width of lubrication pocket m
P
B Nominal bearing width m
B Length of the axial housing m
H
c Specific heat capacity of the lubricant J/(kg·K)
p
C Nominal bearing clearance m
C Effective bearing radial clearance m
R,eff
d Lubrication hole diameter m
L
D Nominal bearing diameter (inside diameter) m
D Length of the outside diameter of the housing m
H
D Nominal shaft diameter m
J
D Maximum value of D m
J,max J
D Minimum value of D m
J,min J
D Maximum value of D m
max
D Minimum value of D m
min
e Eccentricity between the axis of the shaft and the bearing axis m
f Coefficient of friction in the loaded area of the lubricant film ( f = F /F) 1
f
f′ Coefficient of friction in both the loaded and unloaded area of
...

INTERNATIONAL ISO
STANDARD 7902-1
Third edition
2020-06
Hydrodynamic plain journal bearings
under steady-state conditions —
Circular cylindrical bearings —
Part 1:
Calculation procedure
Paliers lisses hydrodynamiques radiaux fonctionnant en régime
stabilisé — Paliers circulaires cylindriques —
Partie 1: Méthode de calcul
Reference number
©
ISO 2020
© ISO 2020
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 2020 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and units . 1
5 Basis of calculation, assumptions, and preconditions . 5
5.1 Reynolds equation . 5
5.2 Assumptions and preconditions . 5
5.3 Boundary conditions . 5
5.4 Basis of calculation . 6
5.5 Permissible operational parameters . 6
6 Calculation procedure . 6
6.1 General . 6
6.2 Freedom from wear . 6
6.3 The limits of mechanical loading. 7
6.4 The limits of thermal loading . 7
6.5 Influencing factors . 7
6.6 Reynolds number . 7
6.7 Calculation factors . 7
7 Definition of symbols . 9
7.1 Load-carrying capacity . 9
7.2 Frictional power loss . 9
7.3 Lubricant flow rate .10
7.3.1 General.10
7.3.2 Lubricant feed elements .10
7.3.3 Lubrication grooves .10
7.3.4 Lubrication pockets .10
7.3.5 Lubricant flow rate .11
7.4 Heat balance .11
7.4.1 General.11
7.4.2 Heat dissipation by convection .12
7.4.3 Heat dissipation via the lubricant .12
7.5 Minimum lubricant film thickness and specific bearing load .13
7.6 Operational conditions.14
7.7 Further influencing factors .14
Annex A (informative) Calculation examples .17
Bibliography .32
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 123, Plain bearings, Subcommittee SC 8,
Calculation methods for plain bearings and their applications.
This third edition cancels and replaces the second edition (ISO 7902-1:2013), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— subclause titles have been added;
— symbols have been corrected and added in Table 1;
— calculation values in Annex A have been corrected;
— adjustments have been made to ISO/IEC Directives, Part 2:2018;
— typographical errors have been corrected.
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 © ISO 2020 – All rights reserved

INTERNATIONAL STANDARD ISO 7902-1:2020(E)
Hydrodynamic plain journal bearings under steady-state
conditions — Circular cylindrical bearings —
Part 1:
Calculation procedure
1 Scope
This document specifies a calculation procedure for oil-lubricated hydrodynamic plain bearings, with
complete separation of the shaft and bearing sliding surfaces by a film of lubricant, used for designing
plain bearings that are reliable in operation.
It deals with circular cylindrical bearings having angular spans, Ω, of 360°, 180°, 150°, 120°, and 90°,
the arc segment being loaded centrally. Their clearance geometry is constant except for negligible
deformations resulting from lubricant film pressure and temperature.
The calculation procedure serves to provide dimensions and optimize plain bearings in turbines,
generators, electric motors, gear units, rolling mills, pumps, and other machines. It is limited to steady-
state operation, i.e. under continuously driven operating conditions, with the magnitude and direction
of loading as well as the angular speeds of all rotating parts constant. It can also be applied if a full
plain bearing is subjected to a constant force rotating at any speed. Dynamic loadings (i.e. those whose
magnitude and direction vary with time), such as those that can result from vibration effects and
instabilities of rapid-running rotors, are not taken into account.
NOTE Equivalent calculation procedures exist that enable operating conditions to be estimated and checked
against acceptable conditions. The use of them is equally admissible.
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 7902-2, Hydrodynamic plain journal bearings under steady-state conditions — Circular cylindrical
bearings — Part 2: Functions used in the calculation procedure
ISO 7902-3, Hydrodynamic plain journal bearings under steady-state conditions — Circular cylindrical
bearings — Part 3: Permissible operational parameters
3 Terms and definitions
No terms and definitions are listed in this document.
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/
4 Symbols and units
Symbols and units are defined in Figure 1 and Table 1.
Figure 1 — Illustration of symbols
Table 1 — Symbols and their designations
Symbol Designation Unit
A Area of heat-emitting surface (bearing housing) m
b Width of lubrication groove m
G
b Width of lubrication pocket m
P
B Nominal bearing width m
B Length of the axial housing m
H
c Specific heat capacity of the lubricant J/(kg·K)
p
C Nominal bearing clearance m
C Effective bearing radial clearance m
R,eff
d Lubrication hole diameter m
L
D Nominal bearing diameter (inside diameter) m
D Length of the outside diameter of the housing m
H
D Nominal shaft diameter m
J
D Maximum value of D m
J,max J
D Minimum value of D m
J,min J
D Maximum value of D m
max
D Minimum value of D m
min
e Eccentricity between the axis of the shaft and the bearing axis m
f Coefficient of friction in the loaded area of the lubricant film ( f = F /F) 1
f
f′ Coefficient of friction in both the loaded and unloaded area of
...