SIST ISO 7146-1:2009

INTERNATIONAL ISO
STANDARD 7146-1
First edition
2008-10-15
Plain bearings — Appearance and
characterization of damage to metallic
hydrodynamic bearings —
Part 1:
General
Paliers lisses — Aspect et caractérisation de l'endommagement des
paliers métalliques à couche lubrifiante fluide —
Partie 1: Généralités
Reference number
©
ISO 2008
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ii © ISO 2008 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Descriptions, causes, and features of damage . 2
4.1 Damage . 2
4.2 Damage causes. 2
4.3 Damage appearances. 2
4.4 Damage characterization . 3
4.5 Relationship between damage appearance and damage characterizations . 3
5 Guidelines for damage analysis. 5
5.1 General. 6
5.2 Step 1 . 6
5.3 Step 2 . 6
5.4 Step 3 . 6
5.5 Step 4 . 6
5.6 Step 5 . 6
6 Damage to the bearing surface — damage characteristics, typical damage appearances
and possible damage causes . 7
6.1 General. 7
6.2 Static overload . 7
6.3 Dynamic overload. 8
6.4 Wear by friction. 15
6.5 Overheating . 18
6.6 Insufficient lubrication (starvation). 20
6.7 Contamination. 25
6.8 Cavitation erosion. 36
6.9 Electro-erosion. 38
6.10 Hydrogen diffusion. 39
6.11 Bond failure . 41
7 Damage to the bearing back. 42
7.1 General. 42
7.2 Dynamic overload on the bearing back.42
7.3 Wear by friction on the bearing back. 44
7.4 Contamination with particles on the bearing back . 46
8 Special position of damage appearances . 47
Annex A (informative) Example of use of Table 1. 50

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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 7146-1 was prepared by Technical Committee ISO/TC 123, Plain bearings, Subcommittee SC 2,
Materials and lubricants, their properties, characteristics, test methods and testing conditions.
This first edition of ISO 7146-1, together with ISO 7146-2, cancels and replaces ISO 7146:1993 the technical
content of which has been technically revised and augmented.
ISO 7146 consists of the following parts, under the general title Plain bearings — Appearance and
characterization of damage to metallic hydrodynamic bearings:
⎯ Part 1: General
⎯ Part 2: Cavitation erosion and its countermeasures

iv © ISO 2008 – All rights reserved

Introduction
In practice, damage to a bearing may often be the result of several mechanisms operating simultaneously. It is
the complex combination of design, manufacture, assembly, operation, maintenance, and possible
reconditioning which often causes difficulty in establishing the primary cause of damage.
In the event of extensive damage or destruction of the bearing, the evidence is likely to be lost, and it will then
be impossible to identify how the damage came about.
In all cases, knowledge of the actual operating conditions of the assembly and the maintenance history is of
the utmost importance.
The classification of bearing damage established in this part of ISO 7146 is based primarily upon the features
visible on the running surfaces and elsewhere, and consideration of each aspect is required for reliable
determination of the cause of bearing damage.
Since more than one process may cause similar effects on the running surface, a description of appearance
alone is occasionally inadequate in determining the cause of damage. Thus Clause 4 is subdivided into
several subclauses including damage appearance and damage characteristics.
For the procedure of damage analysis, Clause 5 may give a helpful guide.
In Clauses 6 and 7, examples of all damage characteristics with typically associated damage appearance are
given.
INTERNATIONAL STANDARD ISO 7146-1:2008(E)

Plain bearings — Appearance and characterization of damage
to metallic hydrodynamic bearings —
Part 1:
General
1 Scope
This part of ISO 7146 defines, describes and classifies the characteristics of damage occurring in service to
hydrodynamically lubricated metallic plain bearings and journals. It assists in the understanding of the various
characteristic forms of damage which may occur.
Consideration is restricted to damage characteristics which have a well-defined appearance and which can be
attributed to particular damage causes with a high degree of certainty. Various appearances are illustrated
with photographs and diagrams.
2 Normative references
The following referenced documents are indispensable for the application 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 4378-1, Plain bearings — Terms, definitions, classification and symbols — Part 1: Design, bearing
materials and their properties
ISO 4378-2, Plain bearings — Terms, definitions, classification and symbols — Part 2: Friction and wear
ISO 4378-3, Plain bearings — Terms, definitions, classification and symbols — Part 3: Lubrication
ISO 4378-4, Plain bearings — Terms, definitions, classification and symbols — Part 4: Basic symbols
ISO 7146-2, Plain bearings — Appearance and characterization of damage to metallic hydrodynamic
bearings — Part 2: Cavitation erosion and its countermeasures
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 4378-1, ISO 4378-2, ISO 4378-3,
ISO 4378-4 and the following apply.
3.1
damage to plain bearings
bearing damage
all changes in appearance occurring on the bearing surface and/or on the bearing back during operation that
adversely affect the performance of the bearing
4 Descriptions, causes, and features of damage
4.1 Damage
4.1.1 General
Damage to plain bearings is a phenomenon that adversely changes their tribological function, usually
accompanied with a change in appearance. The damage is initiated by the damage cause and develops to the
end of service life.
As long as no abnormal conditions occur, service life of the plain bearing relates to the service life of the
machine.
4.1.2 Indicators of damage
Typical indicators observed during machine operation are: continuously increasing service temperature,
decline of lubricant pressure, noise, vibration, and bad smell.
4.2 Damage causes
The cause is the practical event that initiates and leads to damage. The majority of damage causes will be
found outside the bearing.
4.3 Damage appearances
Damage appearance is a defined visible picture of the bearing surface and/or of the bearing back. Damage
appearances are clearly different from each other.
A plain bearing failure can show various damage appearances. Usually damage appearances are directly
associated with damage characteristics, but not directly with the damage cause (for exceptions, see 6.8 and
6.9).
List of damage appearances:
a) depositions;
b) creep deformation;
c) deformation due to temperature cycles;
d) thermal cracks;
e) fatigue cracks;
f) material relief (loss of bond);
g) frictional corrosion;
h) melting out, seizure;
i) polishing, scoring;
j) traces of mixed lubrication, worn material;
k) blue, black colour;
l) corrosion, fluid erosion;
m) embedded particles, particle-migration tracks, formation of wire wool;
n) electric arc craters;
o)
...