ISO 16123:2025

International
Standard
ISO 16123
First edition
Ships and marine technology —
2025-03
Marine cranes — Slewing bearings
Navires et technologie maritime — Grues marines — Supports
d’orientation
Reference number
© ISO 2025
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Classification and designation . 2
4.1 Composition and structure .2
4.2 Designation .3
5 Technical requirements . 4
5.1 Load ratings .4
5.2 Rolling element .4
5.3 Bearing rings .5
5.4 Cage/separator .6
5.5 Sealing ring .6
5.6 Oil cup .6
5.7 Gears of the bearing ring .6
5.8 Residual magnetism limit of the bearing .7
5.9 Accuracy of the slewing bearing .8
5.10 Lubrication .10
5.11 Other requirements .10
6 Inspection requirements . 10
6.1 Inspection items .10
7 Inspection method .11
7.1 Materials .11
7.2 Hardness .11
7.3 Surface cracks of raceway .11
7.4 Ultrasonic testing of bearing rings .11
7.5 Impact energy of bearing ring material .11
7.6 Effective depth of hardening of raceway quenching, D .11
S
7.7 Width of soft zone of raceway quenching .11
7.8 Appearance quality .11
7.9 Dimensional tolerance .11
7.10 Rotation accuracy . 12
7.11 Gear accuracy . 12
7.12 Clearance . 13
7.13 Rotation . 13
8 Marking, packaging, transportation and storage .13
8.1 Marking . 13
8.2 Packaging . 13
8.3 Transportation and storage . 13
9 Installation and maintenance . . 14
Annex A (informative) Installation and maintenance of slewing bearing .15
Bibliography . 17

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 8, Ships and marine technology, Subcommittee
SC 4, Outfitting and deck machinery.
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iv
International Standard ISO 16123:2025(en)
Ships and marine technology — Marine cranes — Slewing
bearings
1 Scope
This document provides requirements on the classification, designation, inspection, testing method, marking,
packaging, transportation, storage, installation and maintenance of slewing bearings for marine cranes.
This document is applicable to the design, manufacture and acceptance of slewing bearings for marine
cranes at an ambient temperature not lower than −40 °C.
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 54, Cylindrical gears for general engineering and for heavy engineering — Modules
ISO 683-2, Heat-treatable steels, alloy steels and free-cutting steels — Part 2: Alloy steels for quenching and
tempering
ISO 683-17, Heat-treatable steels, alloy steels and free-cutting steels — Part 17: Ball and roller bearing steels
ISO 898-1, Mechanical properties of fasteners made of carbon steel and alloy steel — Part 1: Bolts, screws and
studs with specified property classes — Coarse thread and fine pitch thread
ISO 898-2, Fasteners — Mechanical properties of fasteners made of carbon steel and alloy steel — Part 2: Nuts
with specified property classes
ISO 1122-1, Vocabulary of gear terms — Part 1: Definitions related to geometry
ISO 1132-1, Rolling bearings — Tolerances — Part 1: Terms and definitions
ISO 1328-1, Cylindrical gears — ISO system of flank tolerance classification — Part 1: Definitions and allowable
values of deviations relevant to flanks of gear teeth
ISO 1328-2, Cylindrical gears — ISO system of flank tolerance classification — Part 2: Definitions and allowable
values of double flank radial composite deviations
ISO 3290-1, Rolling bearings — Balls — Part 1: Steel balls
ISO 3452-2, Non-destructive testing — Penetrant testing — Part 2: Testing of penetrant materials
ISO 5593, Rolling bearings — Vocabulary
ISO 6506-1, Metallic materials — Brinell hardness test — Part 1: Test method
ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel
ISO 9934 (all parts), Non-destructive testing — Magnetic particle testing
ISO/TR 10064-2:1996, Code of inspection practice — Part 2: Inspection related to radial composite deviations,
runout, tooth thickness and backlash
ISO 14556, Metallic materials — Charpy V-notch pendulum impact test — Instrumented test method

ISO 15241, Rolling bearings — Symbols for physical quantities
ISO 16396-1, Plastics — Polyamide (PA) moulding and extrusion materials — Part 1: Designation system and
basis for specifications
ISO 16396-2:2022, Plastics — Polyamide (PA) moulding and extrusion materials — Part 2: Preparation of test
specimens and determination of properties
ISO 16859-1, Metallic materials — Leeb hardness test — Part 1: Test method
ISO 18203, Steel — Determination of the thickness of surface-hardened layers
EN 10228-1, Non-destructive testing of steel forgings — Part 1: Magnetic particle inspection
EN 10228-2, Non-destructive testing of steel forgings — Part 2: Penetrant testing
EN 10228-3:2016, Non-destructive testing of steel forgings — Part 3: Ultrasonic testing of testing of ferritic or
martensitic steel forgings
ISO 10474:2013, Steel and steel products — Inspection documents
3 Terms and definitions
For the purpose of this document, the terms and definitions given in ISO 1132-1, ISO 5593 and ISO 15241 and
the following apply.
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/
3.1
crane slewing bearing
structure connecting the crane and the base, provided with mounting holes inside and outside, which is a
large rolling bearing capable of bearing combined loads (axial and radial loads and tilting moments) and
transmitting large torques
4 Classification and designation
4.1 Composition and structure
A slewing bearing consists of bearing rings (inner rings, outer rings), a rolling element, a cage/separator, a
sealing ring and an oil cup. There are three types of slewing bearings according to their structural forms:
a) Single-row four-point contact ball slewing bearing (see Figure 1)
Figure 1 — Single-row four-point contact ball slewing bearing

b) Double-row reducing ball slewing bearing (see Figure 2)
Figure 2 — Double-row reducing ball slewing bearing
c) Three-row cross-roller slewing bearing (see Figure 3)
Figure 3 — Three -row cross-roller slewing bearing
4.2 Designation
The model representation of slewing bearings is shown in Figure 4. If other codes such as change in material,
gear surface requirements, heat treatment mode of the raceway, tolerance grade and sealing structure are
required, they shall be marked after the diameter of the raceway centre circle, separated by a space.
Figure 4 — Model representation of slewing bearings
EXAMPLE The marine internal gear type three-row roller slewing bearing with the diameter of the upper row
rolling element of 40 mm and the diameter of the raceway centre circle of 2 500 mm:
Crane slewing bearing-ISO 16123-03-1-40–2500

5 Technical requirements
5.1 Load ratings
The static and dynamic load ratings of the slew bearings can be calculated based on ISO 76 and ISO 16281,
respectively.
5.2 Rolling element
5.2.1 Materials shall conform to the requirements on 100CrMnsi6 and 100Cr for bearing steel in
ISO 683-17. Other materials that meet the performance may also be used.
5.2.2 Steel balls shall conform to ISO 3290-1 and their tolerance grades shall be in accordance with Table 1.
Table 1 — Tolerance grade of steel ball
Diameter
D
Tolerance grade of steel ball
w
mm
D ≤ 30 G40
w
30 < D ≤ 50 G60
w
D > 50 G100
w
5.2.3 Tolerances of the cylindrical roller shall be in accordance with Table 2.
Table 2 — Tolerances of cylindrical roller
Rolling
Outer diameter
Face Chamfer
Diameter Length face
surface
Diameter surface roundness
roughness roughness
variation runout
roughness
error
D
w
V S
DWL DW
Δ
R
mm
Rw
a,max
μm μm
μm
μm
D ≤ 18 4 1,0 10
w
18 < D ≤ 30 4 1,5 10 0,25 0,32 2,5
w
D > 30 5 2,5 10
w
NOTE The definitions of outer diameter surface roundness error and length face runout are according to ISO 286-2.
5.2.4 The residual magnetism limit of the rolling element shall be in accordance with Table 3.
Table 3 — Residual magnetism limit of rolling element
Nominal diameter
Maximum value of residual
magnetism
Rolling element type D
rolling
m
mm
T
5 < D ≤ 50 0,25
rolling
Steel ball
D > 50 0,3
rolling
10 < D ≤ 18 0,2
rolling
18 < D ≤ 30 0,25
rolling
Cylindrical roller
30 < D ≤ 50 0,3
rolling
D > 50 0,4
rolling
5.3 Bearing rings
5.3.1 Bearing rings shall be manufactured with 42CrMo4 quenched and tempered steel in accordance
with ISO 683-2, quenched and tempered to 260HBW-320HBW. Other materials with the same performance
may be used. An "Inspection Certificate 3.2" shall be obtained in accordance with ISO 10474:2013, 5.2.
NOTE 1 42CrMo4 refers to a brand of steel. HBW refers to Hardness Brinell Wolffran-carbide.
NOTE 2 Inspection Certificate 3.2 refers to a document validated by the manufacture’s authorized inspection
representative and either the purchaser’s authorized representative or an inspector designed by a third party,
declaring that the products supplied comply with the requirements of the order and which test results are supplied
from a specific inspection.
5.3.2 The average value of the Charpy V-notch pendulum impact absorption energy of the ring material
shall be not less than 25 J, and the single specimen value not less than 20 J, at −10 °C or the design temperature,
whichever is lower. The average value shall be not less than 42 J, and the single specimen value not less than
27 J, at −20 °C or the design temperature minus 10 °C, whichever is lower.
5.3.3 The non-destructive testing shall be carried out by testing personnel with at least Level II
qualification, in accordance with ISO 9712, on the blank or finished surface of the bearing ring forging.
5.3.4 The NDT method shall meet the following requirements:
a) magnetic particle testing in accordance with the ISO 9934 series and EN 10228-1;
b) dye penetrant testing in accordance with ISO 3452-2 and EN 10228-2;
c) ultrasonic testing in accordance with EN 10228-3:2016, Clause 14, quality class Level 3.
5.3.5 When the diameter of bearing ring raceway is more than 2 500 mm or the mass of the forging is
greater than 3 000 kg (3 tons), the forging shall be sampled at the positions shown in Figure 5, for mechanical
properties, hardness and impact value, etc. after heat treatment, other than the positions where mechanical
properties does not correspond to the actual stress.
Figure 5 — Bearing ring
5.3.6 The ring raceway shall be quenched to achieve surface hardness of 55 HRC to 63 HRC. The effective
depth of hardening (i.e. the depth of the raceway surface with hardness no less than 48 HRC), D , shall meet
S
the requirements in Table 4. The effecti
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