ISO 12131-1:2020

INTERNATIONAL ISO
STANDARD 12131-1
Second edition
2020-07
Plain bearings — Hydrodynamic plain
thrust pad bearings under steady-
state conditions —
Part 1:
Calculation of thrust pad bearings
Paliers lisses — Butées hydrodynamiques à patins géométrie fixe
fonctionnant en régime stationnaire —
Partie 1: Calcul des butées à segments
Reference number
©
ISO 2020
© 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and units . 2
5 Fundamentals, assumptions and premises . 5
6 Calculation procedure . 6
6.1 Loading operations . 6
6.1.1 General. 6
6.1.2 Wear . 6
6.1.3 Mechanical loading . 6
6.1.4 Thermal loading . 6
6.1.5 Outside influences . 6
6.2 Load carrying capacity . 8
6.3 Frictional power. 9
6.4 Lubricant flow rate . 9
6.5 Heat balance .10
6.5.1 General.10
6.5.2 Heat dissipation by convection .10
6.5.3 Heat dissipation by recirculating lubrication .12
6.6 Minimum lubricant film thickness and specific bearing load .14
6.7 Operating conditions .14
6.8 Further influence factors .15
Annex A (informative) Examples of calculation .16
Bibliography .25
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 12131-1:2001), which has been technically
revised.
The main changes compared to the previous edition are the correction of typographical errors.
A list of all parts in the ISO 12131 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

INTERNATIONAL STANDARD ISO 12131-1:2020(E)
Plain bearings — Hydrodynamic plain thrust pad bearings
under steady-state conditions —
Part 1:
Calculation of thrust pad bearings
1 Scope
The aim of this document is to achieve designs of plain bearings that are reliable in operation, by the
application of a calculation method for oil-lubricated hydrodynamic plain bearings with complete
[1]
separation of the thrust collar and plain bearing surfaces by a film of lubricant .
This document applies to plain thrust bearings with incorporated wedge and supporting surfaces
having any ratio of wedge surface length l to length of one pad L. It deals with the value l /L = 0,75
wed wed
[2]
as this value represents the optimum ratio . The ratio of width to length of one pad can be varied in
the range B/L = 0,5 to 2.
The calculation method described in this document can be used for other incorporated gap shapes, e.g.
plain thrust bearings with integrated baffle, when for these types the numerical solutions of Reynolds
equation are known.
The calculation method serves for designing and optimizing plain thrust bearings e.g. for fans, gear
units, pumps, turbines, electrical machines, compressors and machine tools. It is limited to steady-state
conditions, i.e. load and angular speed of all rotating parts are constant under continuous operating
conditions. Dynamic operating conditions are not included.
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 3448, Industrial liquid lubricants — ISO viscosity classification
ISO 12131-2:2016, Plain bearings — Hydrodynamic plain thrust pad bearings under steady-state
conditions — Part 2: Functions for the calculation of thrust pad bearings
ISO 12131-3, Plain bearings — Hydrodynamic plain thrust pad bearings under steady-state conditions —
Part 3: Guide values for the calculation of thrust pad bearings
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
See Table 1 and Figure 1.
Table 1 — Symbols and units
Symbol Designation Unit
A Heat emitting surface of the bearing housing m
B Width of one pad m
B Axial housing width m
H
Cp Specific heat capacity of the lubricant (p = constant) J/(kg⋅K)
C Wedge depth m
wed
D Mean sliding diameter (diameter of thrust bearing ring) m
D Housing outside diameter m
H
D Inside diameter of thrust bearing ring m
i
D Outside diameter of thrust bearing ring m
o
f* Characteristic value of friction 1
f * Characteristic value of friction for thrust pad bearing 1
B
F Bearing force (nominal load) N
F* Characteristic value of load carrying capacity 1
F * Characteristic value of load carrying capacity for thrust pad bearing 1
B
F Bearing force (load) under stationary conditions N
st
h Local lubricant film thickness (clearance gap height) m
h Minimum permissible lubricant film thickness during operation m
lim
h Minimum permissible lubricant film thickness in the transition into mixed m
lim, tr
lubrication
h Minimum lubricant film thickness (minimum clearance gap height) m
min
k Heat transfer coefficient related to the product B × L × Z W/(m ⋅K)
k External heat transfer coefficient (reference surface A) W/(m ⋅K)
A
l Wedge length m
wed
L Length of one pad in circumferential direction m
M Mixing factor 1
−1
N Rotational frequency (speed) of thrust collar s
p Local lubricant film pressure Pa
p Specific bearing load p = F/(B × L × Z)
Pa
P Frictional power in the bearing or heat flow rate generated by it W
f
Maximum permissible specific bearing load Pa
p
lim
P Heat flow rate to the environment W
th, amb
P Heat flow rate arising from the frictional power W
th, f
P Heat flow rate in the lubricant W
th, L
Q Lubricant flow rate m /s
Q* Characteristic value of lubricant flow rate 1
Q Relative lubricant flow rate Q = B × h × U × Z m /s
0 0 min
Q Lubricant flow rate at the inlet of the clearance gap (circumferential direction) m /s
Q* Characteristic value of lubricant flow rate at the inlet of the clearance gap 1
Q Lubricant flow rate at the outlet of the clearance gap (circumferential direction) m /s
Q* Characteristic value of lubricant flow rate Q* − Q* at the outlet of the clear- 1
2 1 3
ance gap
2 © ISO 2020 – All rights reserved

Table 1 (continued)
Symbol Designation Unit
Q Lubricant flow rate at the sides (perpendicular to circumferential direction) m /s
Q* Characteristic value of lubricant flow rate at the sides 1
Re Reynolds number 1
Critical Reynolds' number 1
Re
cr
T Ambient temperature °C
amb
T Bearing temperature °C
B
T Effective lubricant film temperature °C
eff
T Lubricant temperature at the inlet of the bearing °C
en
T Lubricant temperature at the outlet of the bearing °C
ex
T Maximum permissible bearing temperature °C
lim
T Lubricant temperature at the inlet of the clearance gap °C
T Lubricant temperature at the outlet of the clearance gap °C
U Sliding velocity relative to mean diameter of bearing ring m/s
w Velocity of air surrounding the bearing housing m/s
amb
x Coordinate in direction of motion (circumferential direction) m
y Coordinate in direction of lubrication clearance gap (axial) m
z Coordinate perpendicular to the direction of motion (radial) m
Z Number of pads 1
η Dynamic viscosity of the lubricant Pa⋅s
η Effective dynamic viscosity of the lubricant Pa⋅s
eff
ρ Density of the lubricant kg/m
ISO 12131-1:20
...