ISO 12131-2:2023

INTERNATIONAL ISO
STANDARD 12131-2
Third edition
2023-06
Plain bearings — Hydrodynamic plain
thrust pad bearings under steady-
state conditions —
Part 2:
Functions for the calculation of thrust
pad bearings
Paliers lisses — Butées hydrodynamiques à patins géométrie fixe
fonctionnant en régime stationnaire —
Partie 2: Fonctions pour le calcul des butées à segments
Reference number
© ISO 2023
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols, terms and units .1
5 Functions for the thrust pad bearing . 2
5.1 Load carrying capacity . 2
5.2 Friction for thrust pad bearings . 4
5.3 Relative lubricant flow rates . 6
6 Effective dynamic viscosity of the lubricant, η , as a function of the effective
eff
lubricant film temperature, T . 9
eff
Bibliography .11
iii
Foreword
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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 12131-2:2016), which has been
technically revised.
The main changes are as follows:
— Formula (1) has been corrected;
— Table 1 has been added;
— some editorial corrections have been made.
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
Introduction
Assuming hydrodynamic conditions with full lubrication, the functions of the type covered by this
document are necessary for the calculation of oil-lubricated pad thrust bearings in accordance with
ISO 12131-1. They are based on the premises and boundary conditions specified. The values necessary
for the calculation can be determined by means of the given formulae, as well as from diagrams and
tables. The formulae in this document are approximations of the numerically determined values traced
as curves according to Reference [2]. The explanation of the symbols, as well as examples for the
calculation, are included in ISO 12131-1.
v
INTERNATIONAL STANDARD ISO 12131-2:2023(E)
Plain bearings — Hydrodynamic plain thrust pad bearings
under steady-state conditions —
Part 2:
Functions for the calculation of thrust pad bearings
1 Scope
This document specifies functions for thrust pad bearings. It also covers the effect of dynamic viscosity
on lubricant film temperature.
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 12131-1:2020, Plain bearings — Hydrodynamic plain thrust pad bearings under steady-state conditions
— Part 1: Calculation of thrust pad bearings
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, terms and units
Symbols and units are defined in Table 1. Any symbols not listed in Table 1 shall be defined in accordance
with ISO 12131-1:2020, Table 1.
Table 1 — Symbols, terms, and units
Symbol Term Unit
i (index) Consecutive number 1
*
A , A , A , A Auxiliary quantity 1
1 3 i
*
B , B , B , B Auxiliary quantity 1
1 3 i
*
C Auxiliary quantity 1
K “Thickness” of oil Pa·s
K Inherent viscosity-temperature dependence of oil °C
K Oil temperature for infinite viscosity °C
VG ISO Viscosity Grade 1
α Auxiliary quantity 1
η Constant coefficient Pa·s
x
5 Functions for the thrust pad bearing
5.1 Load carrying capacity
*
Characteristic value of load carrying capacity, F , as a function of the relative bearing length, B/L, and
B
the relative minimum lubricant film thickness, h /C is defined by Formula (1) using the auxiliary
min wed
* * *
quantities α, A , B and C .
Approximation of the curves of Figure 1 (range of application: 0,1 ≤ h /C ≤ 10).
min wed
 
l  h  1 + hC/
 
wed min min wed
 ×  × ln 
   
L C h /C
 
   
wed miin wed
 


*
 
2 2
F =×5
B
l 1 l l  h l 
       
wed wedwed min wed
×
...