ISO 4378-3:2024
(Main)Plain bearings — Terms, definitions, classification and symbols — Part 3: Lubrication
Plain bearings — Terms, definitions, classification and symbols — Part 3: Lubrication
This document specifies the most commonly used terms relating to lubrication of plain bearings with their definitions and classification. For some terms and word combinations, their short forms are given, which can be used where they are unambiguous.
Paliers lisses — Termes, définitions, classification et symboles — Partie 3: Lubrification
L'ISO 4378-3:2017 spécifie les termes les plus couramment utilisés en matière de lubrification, ainsi que leur définition et leur classification. Les formes abrégées données pour certains termes peuvent être employées dans les cas où elles ne créent aucune ambiguïté possible quant à leur interprétation. Les termes suffisamment explicites par eux-mêmes ne sont pas définis.
General Information
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Standards Content (Sample)
International
Standard
ISO 4378-3
Fourth edition
Plain bearings — Terms, definitions,
2024-11
classification and symbols —
Part 3:
Lubrication
Paliers lisses — Termes, définitions, classification et symboles —
Partie 3: Lubrification
Reference number
© ISO 2024
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 General terms .1
3.2 Terms related to the types of lubrication and classification .1
3.2.1 Classification according to physical state of the lubricant .1
3.2.2 Classification according to the mechanism of separation of the interacting
surfaces by a lubricant film .2
3.2.3 Calculation model for the EHD and THD lubrication condition .3
3.3 Terms related to methods of lubrication and classification .4
3.3.1 Classification according to periodicity of application of lubricant .4
3.3.2 Classification according to the methods of renewing the lubricant .4
3.3.3 Classification according to the method of application of the lubricant to the
friction surface .4
3.4 Terms related to lubricants, their components and types . 12
3.4.1 Terms related to type according to the physical state of lubricant . 12
3.4.2 Terms related to type according to the presence of additive . 12
3.4.3 Terms related to type according to the origin of lubricant . 13
3.4.4 Terms related to type according to the type of additive . 13
3.4.5 Terms related to type according to the application of lubricant . 15
3.5 Basic characteristics of lubricants . 15
Bibliography . 17
Index .18
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
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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 6, Terms
and common items.
This fourth edition cancels and replaces the third edition (ISO 4378-3:2017), which has been technically
revised.
The main changes are as follows:
— editorial revision of the document: instead of referring to the parts in the figure by subclause number,
the part numbers have been used and the names in the key have been shown.
— addition of alphabetical index.
A list of all parts in the ISO 4378 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
As there is a large number of multiple designations in the domain of plain bearings, there is a considerable
risk of error in the interpretation of standards and technical literature.
This document is an attempt to establish a uniform basic system of designations of lubrication.
in addition, this document is specifically intended for the field of plain bearings the content can be adopted
in general to the field of tribology and being adopted to other machinery elements.
v
International Standard ISO 4378-3:2024(en)
Plain bearings — Terms, definitions, classification and
symbols —
Part 3:
Lubrication
1 Scope
This document specifies the most commonly used terms relating to lubrication of plain bearings with their
definitions and classification.
For some terms and word combinations, their short forms are given, which can be used where they are
unambiguous.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
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 https:// www .electropedia .org/
3.1 General terms
3.1.1
lubrication
technique to reduce friction force, wear and deterioration of the surfaces of two bodies in contact and in
relative motion due to the action and effect of lubricant
3.1.2
method of lubrication
method of supplying lubricant into the space between two bodies in contact and in relative motion
3.2 Terms related to the types of lubrication and classification
3.2.1 Classification according to physical state of the lubricant
3.2.1.1
gas-film lubrication
lubrication (3.1.1) in which the interacting surfaces in relative motion are separated by a gaseous lubricant
3.2.1.2
liquid-film lubrication
lubrication (3.1.1) in which the interacting surfaces in relative motion are separated by a liquid lubricant
3.2.1.3
fluid-film lubrication
lubrication (3.1.1) in which the interacting surfaces in relative motion are separated by a fluid lubricant (gas
or liquid)
3.2.1.4
solid-film lubrication
lubrication (3.1.1) in which the interacting surfaces in relative motion are separated by a solid lubricant
(3.4.1.4)
3.2.2 Classification according to the mechanism of separation of the interacting surfaces by a
lubricant film
3.2.2.1
hydrodynamic lubrication
lubrication (3.1.1) in which the interacting surfaces in relative motion are completely separated by the
pressure generated in the fluid film between these surfaces due to their relative motion and the viscosity
(3.5.1) of the fluid
3.2.2.2
hydrostatic lubrication
lubrication (3.1.1) in which the interacting surfaces, either in relative motion or in a state of rest, are
completely separated by supplying high-pressure fluid between the interacting surfaces from the outside
3.2.2.3
aerodynamic lubrication
lubrication (3.1.1) in which the interacting surfaces in relative motion are completely separated by the
pressure generated in the gas film between these surfaces due to their relative motion and the viscosity
(3.5.1) of the gas
3.2.2.4
aerostatic lubrication
lubrication (3.1.1) in which the interacting surfaces, either in relative motion or in a state of rest, are
completely separated by supplying high-pressure gas between the interacting surfaces from the outside
3.2.2.5
boundary lubrication
lubrication (3.1.1) in which friction between, and wear of, two surfaces in relative motion are governed by
the properties of the surface and by the properties of the lubricant other than bulk viscosity (3.5.1)
3.2.2.6
mixed-film lubrication
mixed lubrication
partial-film lubrication
lubrication (3.1.1) in which there is fluid-film lubrication (3.2.1.3) and boundary lubrication (3.2.2.5)
3.2.2.7
laminar flow lubrication
lubricating condition in which the molecules of the lubricant fluid move steadily and regularly, forming
smooth streamlines
Note 1 to entry: This condition appears in a flow in which the viscous force prevails over the inertia force, or where the
Reynolds number is relatively small and the Taylor number is less than a critical value.
3.2.2.8
non-laminar flow lubrication
lubricating condition for which the flow is not laminar and which includes transition and turbulent flow
lubrication (3.2.2.10)
3.2.2.9
transition flow lubrication
Taylor flow lubrication
lubricating condition in which the stream lines are not smooth, but the turbulence is not fully developed
Note 1 to entry: Depending on the operating conditions, the Taylor vortexes can occur or not.
3.2.2.10
turbulent flow lubrication
lubricating condition in which the molecules of the lubricant move in an unsteady and irregular manner in
time and space or in a turbulent manner
Note 1 to entry: This condition appears in a flow in which the inertia force prevails over viscous force or where the
Reynolds number is large and the Taylor number is greater than a critical value.
3.2.2.11
starved lubrication
lubricating condition in which lubricant is insufficiently supplied between surfaces to be lubricated
3.2.2.12
non-lubrication
condition of relative motion without lubrication (3.1.1)
3.2.2.13
oil-free lubrication
lubricating condition in which interacting surfaces in relative motion are not lubricated by oil
3.2.2.14
grease lubrication
lubrication (3.1.1) in which grease (3.4.1.3) is used as lubricant
3.2.2.15
water lubrication
lubrication (3.1.1) in which water or sea water is used as lubricant
3.2.3 Calculation model for the EHD and THD lubrication condition
3.2.3.1
elasto-hydrodynamic lubrication
EHL
EHD
lubrication (3.1.1) in which the pressure, the friction force and the lubricant film thickness between the interacting
surfaces in relative motion are governed by the elastic properties of the materials of contacting bodies, as well as
the rheological properties of the lubricant, especially the pressure dependence of viscosity (3.5.1)
3.2.3.1.1
hard EHL
elasto-hydrodynamic lubrication (3.2.3.1) in which the effect of elastic deformation of interacting surfaces in
relative motion, and the exponential
...
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