Hydrodynamic plain journal bearings under steady-state conditions — Circular cylindrical bearings — Part 3: Permissible operational parameters

This document specifies empirical permissible values for hlim, Tlim and . 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.

Paliers lisses hydrodynamiques radiaux fonctionnant en régime stabilisé — Paliers circulaires cylindriques — Partie 3: Paramètres opérationnels admissibles

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Status
Published
Publication Date
08-Jun-2020
Current Stage
6060 - International Standard published
Start Date
16-Apr-2020
Completion Date
09-Jun-2020
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ISO 7902-3:2020 - Hydrodynamic plain journal bearings under steady-state conditions -- Circular cylindrical bearings
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INTERNATIONAL ISO
STANDARD 7902-3
Second edition
2020-06
Hydrodynamic plain journal 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 7902-3:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO 7902-3:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© 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
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Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 7902-3:2020(E)
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

© ISO 2020 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 7902-3:2020(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 123, Plain bearings, Subcommittee SC 8,

Calculation methods for plain bearings and their applications.

This second edition cancels and replaces the first edition (ISO 7902-3:1998), of which it constitutes a

minor revision. The changes compared to the previous edition are as follows:
— adjustment to ISO/IEC Directives, Part 2:2018;
— correction of typographical errors.
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
---------------------- Page: 4 ----------------------
ISO 7902-3:2020(E)
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 or T and p do not lie above or below the permissible operational parameters h , T and

min B ex lim lim

p . The permissible parameters represent geometrically and technologically dependent operational

lim

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).
© ISO 2020 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 7902-3:2020(E)
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, 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 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 Table 1. ISO 7902-1:2020, Table 1 shall be referenced to identify the

meaning of symbols not listed in Table 1.
Table 1 — Symbols and their designations
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
h Maximum permissible effective waviness m
wav,eff,lim
h Maximum permissible waviness m
wav,lim
© ISO 2020 – All rights reserved 1
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ISO 7902-3:2020(E)
Table 1 (continued)
i Number of waviness 1
l Length of lubrication groove m
l Length of lubricant pocket m
L Length of bearing housing m
N Rotational frequency of the bearing force s
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
Rz Average peak-to-valley height of shaft mating surface m
y Amount of deflection m
γ Angle of misalignment of the shaft rad
Period of waviness °
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

lim

transition to mixed friction (see ISO 7902-1:2020, 7.6), can be determined from the following formula as

shown in Figure 1.
1 1
hR=+zRzB+⋅yy++h (1)
limB Jwav,eff
2 2
Formula (1) takes into account

— the sum of the mean peak-to-valley heights of bearing and shaft at the ideal location (line X-X)

[Rz + Rz ],
B J
— the mi
...

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