ISO 7902-3:2026
(Main)Hydrodynamic plain journal bearings under steady-state conditions — Circular cylindrical bearings — Part 3: Permissible operational parameters
- Abstract
This document specifies empirical permissible values for hlim, Tlim and plim . 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.
- Status
- Published
- Publication Date
- 18-May-2026
- Current Stage
- 6060 - International Standard published
- Start Date
- 19-May-2026
- Due Date
- 03-May-2027
- Completion Date
- 19-May-2026
ISO 7902-3:2026 is an ISO International Standard for hydrodynamic plain journal bearings under steady-state conditions, specifically circular cylindrical bearings. It specifies empirical permissible operational parameters for minimum lubrication film thickness hlim, maximum permissible bearing temperature Tlim and maximum permissible specific bearing load plim for engineers, manufacturers and users checking whether a bearing design and operating point stay within acceptable limits.
What does ISO 7902-3:2026 specify?
ISO 7902-3:2026 gives empirical allowable values for the key operating limits used with circular cylindrical hydrodynamic plain journal bearings. The document is organized around the practical checks a designer or buyer needs: wear, mechanical loading, thermal loading and bearing clearance.
Clause 4 provides the symbols and units used in the calculations, and Table 1 points readers to ISO 7902-1 when a symbol is not listed there. The document then moves from wear-related limits to load, temperature and clearance, so the reader can check a bearing in the same order as the operating risks.
What are the key requirements of ISO 7902-3:2026?
Clause 4 establishes the calculation language. Readers need the defined symbols and units before they can use the empirical limits in later clauses, and any symbol not listed in Table 1 is taken from ISO 7902-1.
Avoiding wear
Clause 5.1 links hlim to complete lubrication and low wear. ISO 7902-3:2026 explains that clean lubricant matters because contamination can raise wear, cause scoring and create local overheating, so filtering may be needed in practice.
The minimum film thickness depends on surface roughness, misalignment and deflection. Table 2 gives empirical values by shaft diameter and sliding speed, which lets a user select a practical minimum film thickness without building a full tribological model.
Clause 5.2 adds effective waviness, hwav,eff, for sliding surfaces with circumferential waviness. Figures 2 and 3 show how waviness amplitude, period and number of waves are related, and they are used to check the worst shaft position against hlim and the maximum permissible waviness.
Avoiding excessive mechanical loading
Clause 6 sets plim to prevent harmful deformation and cracking of the sliding surfaces. The clause also says the starting load should be checked separately, because high starting specific load may call for pressurized oil assistance.
Table 3 gives empirical permissible values for bearing material groups. In practice, that means the material selection is part of the load check, not just a manufacturing detail.
Avoiding excessive thermal loading
Clause 7 sets Tlim for the bearing system. ISO 7902-3:2026 notes that higher temperature reduces bearing material strength and lubricant viscosity, and that mineral-oil lubricants age faster above 80 °C.
For steady-state calculations, the bearing temperature TB or the lubricant outlet temperature Tex may be used if they remain below Tlim. Table 4 gives values for force-feed lubrication and lubrication without pressure, so the reader can relate thermal limits to the lubrication method and lubricant supply.
Bearing clearance
Clause 8 treats the mean relative bearing clearance, ψ, as a practical operating parameter. It gives an approximate relationship with peripheral speed U and then preferred clearance steps, while Table 5 gives empirical values by shaft diameter and speed.
The clause also warns that shaft temperature, elastic deformation, thermal expansion differences and unusual lubricant viscosity can shift the result. In practice, that means clearance is chosen from operating conditions, not from diameter alone.
What terms does ISO 7902-3:2026 define?
- hlim - the minimum permissible lubrication film thickness needed to keep the bearing in full lubrication as far as possible.
- hwav,eff - the effective waviness of the sliding surface, used when circumferential waviness affects the operating check.
- plim - the maximum permissible specific bearing load selected to avoid damaging mechanical deformation and cracks.
- Tlim - the maximum permissible bearing temperature used to limit thermal loading of the bearing and lubricant.
- ψ - the mean relative bearing clearance, expressed in thousandths, used in the clearance selection.
- U - the peripheral speed, which is used in the clearance guidance and in the empirical value tables.
- Tex - the lubricant outlet temperature, which may be used instead of bearing temperature in steady-state thermal checks.
Who uses ISO 7902-3:2026?
ISO 7902-3:2026 is used by bearing design engineers, tribology specialists, machine builders and suppliers working with hydrodynamic plain journal bearings. It is also useful for quality and application teams that need to check whether the selected bearing geometry, lubrication, load and temperature conditions match the permissible operating range. Buyers and specification writers can use it when setting operating limits for rotating equipment that uses circular cylindrical plain bearings.
What changed in ISO 7902-3:2026 from the previous edition?
ISO 7902-3:2026 is the third edition and replaces ISO 7902-3:2020. The stated revision is minor, and the introduction adds a note on equivalent calculation procedures.
Which standards are used with ISO 7902-3:2026?
| Standard | Contribution |
|---|---|
| ISO 7902-1:2026 | Calculation procedure, symbol meanings and calculation examples for the ISO 7902 series. |
| ISO 286-2 | Tolerance classes for holes and shafts, relevant to the bearing clearance discussion. |
| ISO 4381 | Material group reference for tin casting alloys in Table 3. |
| ISO 4382-1 | Material group reference for cast copper alloys in Table 3. |
| ISO 4382-2 | Material group reference for wrought copper alloys in Table 3. |
| ISO 4383 | Material group reference for multilayer materials in Table 3. |
What does the ISO 7902-3:2026 document contain?
ISO 7902-3:2026 contains one symbol-and-units table, three figures and four tables of empirical operating limits. The figures support the film-thickness and waviness calculations, while the tables give practical values for minimum film thickness, permissible load, permissible temperature and bearing clearance.
Clause 5 includes a worked calculation example for waviness, which helps users apply the method to real geometry and surface data. The bibliography points to standards on tolerance classes and plain-bearing materials that support the clearance and material discussions.
Relations
- Effective Date
- 08-Nov-2025
Frequently Asked Questions
ISO 7902-3:2026 is a standard published by the International Organization for Standardization (ISO). Its full title is "Hydrodynamic plain journal bearings under steady-state conditions — Circular cylindrical bearings — Part 3: Permissible operational parameters". This standard covers: This document specifies empirical permissible values for hlim, Tlim and plim . 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.
This document specifies empirical permissible values for hlim, Tlim and plim . 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.
ISO 7902-3:2026 is classified under the following ICS (International Classification for Standards) categories: 21.100.10 - Plain bearings. The ICS classification helps identify the subject area and facilitates finding related standards.
ISO 7902-3:2026 has the following relationships with other standards: It is inter standard links to ISO 7902-3:2020. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
ISO 7902-3:2026 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
International
Standard
ISO 7902-3
Third edition
Hydrodynamic plain journal
2026-05
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 2026
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Published in Switzerland
ii
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
iii
Foreword
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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
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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)
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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 7902-3:2020), of which it constitutes a minor
revision.
The changes are as follows:
— a note on equivalent calculation procedures has been added to the introduction.
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
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
min B
or T and p do not lie above or below the permissible operational parameters h , T and p . The
ex lim lim
lim
permissible parameters represent geometrically and technologically dependent operational 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).
NOTE Equivalent calculation procedures exist that enable operating conditions to be estimated and checked
against acceptable conditions. Another calculation procedure is equally admissible.
v
International Standard ISO 7902-3:2026(en)
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 7902-1:2026, 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 terminology 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/
4 Symbols and units
Symbols and units are defined in Table 1. ISO 7902-1:2026, Table 1 shall be referenced to identify the meaning
of symbols not listed in Table 1.
Table 1 — Symbols and their designations
Symbol Designation Unit
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
TTabablele 1 1 ((ccoonnttiinnueuedd))
Symbol Designation Unit
h Maximum permissible effective waviness m
wav,eff,lim
h Maximum permissible waviness m
wav,lim
i Number of waves 1
l Length of lubrication groove m
G
l Length of lubricant pocket m
P
L Length of bearing housing m
H
−1
N Rotational frequency of the bearing force s
F
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
B
Rz Average peak-to-valley height of shaft mating surface m
J
y Amount of deflection m
γ Angle of misalignment of the shaft rad
Period of waviness °
ϕ
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 transition to
lim
...