National foreword

This British Standard is the UK implementation of ISO 7902‑1:2020. It supersedes BS ISO 7902‑1:2013, which is withdrawn.

The UK participation in its preparation was entrusted to Technical Committee MCE/12, Plain bearings.

A list of organizations represented on this committee can be obtained on request to its secretary.

This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 July 2020.

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.

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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.

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

3 Terms and definitions

4 Symbols and units

5 Basis of calculation, assumptions, and preconditions

5.1 Reynolds equation

5.2 Assumptions and preconditions

5.3 Boundary conditions

5.4 Basis of calculation

5.5 Permissible operational parameters

6 Calculation procedure

6.1 General

6.2 Freedom from wear

6.3 The limits of mechanical loading

6.4 The limits of thermal loading

6.5 Influencing factors

6.6 Reynolds number

6.7 Calculation factors

7 Definition of symbols

7.1 Load-carrying capacity

7.2 Frictional power loss

7.3 Lubricant flow rate

7.4 Heat balance

7.5 Minimum lubricant film thickness and specific bearing load

7.6 Operational conditions

7.7 Further influencing factors

Bibliography

BS ISO 7902-1:2020

Hydrodynamic plain journal bearings under steady-state conditions. Circular cylindrical bearings - Calculation procedure

Current, Under Review

Published:

31 Jul 2020