ISO 8838:2024

International
Standard
ISO 8838
First edition
Plain bearings — Water-lubricated
2024-09
plain bearing materials
Paliers lisses — Matériaux de paliers lisses lubrifiés à l'eau
Reference number
© ISO 2024
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Plain bearing materials and mating (shafts) materials . 2
4.1 Bearing materials . .2
4.1.1 General .2
4.1.2 Wood-based material .2
4.1.3 Carbon-based material .2
4.1.4 Rubber-based material .2
4.1.5 Thermosetting resin-based material .2
4.1.6 Fluoro resin-based material .3
4.1.7 Thermoplastic resin-based material .3
4.1.8 Ceramic-based material .3
4.1.9 Cermet-based material .3
4.2 Mating (shaft) materials.3
4.2.1 General .3
4.2.2 Copper alloy .3
4.2.3 Stainless steel .3
4.2.4 Plating .3
4.2.5 Ceramics .4
4.2.6 Cermet.4
5 Characteristics, applications, manufacturing method and compatible combinations . 4
6 Water supply method . 4
6.1 General .4
6.2 Forced water supply .4
6.3 Circulating water supply .4
6.4 Immersed in water .4
7 Design considerations . 5
7.1 General .5
7.2 Water temperature .5
7.3 Removal of foreign matters .5
7.3.1 General .5
7.3.2 Methods of removing foreign matters .5
7.4 Operating conditions .6
Annex A (informative) Characteristics, applications, manufacturing methods and compatible
combinations . 7
Annex B (informative) Precautions on sources of lubricating water .13
Bibliography . 14

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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The procedures used to develop this document and those intended for its further maintenance are described
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This document was prepared by Technical Committee ISO/TC 123, Plain bearings, Subcommittee SC 7, Special
types of plain bearings.
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
Water-lubricated bearings are widely used in fields such as submersible pumps, marine stern tubes,
hydroelectric generator turbines, water treatment equipment, water valves and rolling equipment for
steelmaking.
Water-lubricated plain bearings are used for the following conditions or reasons:
a) oil or greases cannot be used due to equipment usage conditions;
b) there is plenty of water available as a lubricant around the equipment;
c) even if water for lubrication leaks, it does not pollute the environment like oil or grease.
However, when using water as a lubricant, it is necessary to take the following into account:
— water freezes at 0 °C or below and becomes vapor at 100 °C or above, at normal pressure, therefore losing
load carrying capacity;
— water has low viscosity in comparison with oil;
— water cannot support a high load because the increase in viscosity that occurs in oil lubrication
(elastohydrodynamic lubrication: EHL) when it is under high pressure cannot be expected in water.
— water does not have the ability that oil and grease have to prevent corrosion on shafts and bearings.
While water-lubricated plain bearings have been used in various fields around the world and the water
that is used as a lubricant has its own specific features differing from oil, there have been no International
Standards that apply to water-lubricated plain bearings thus far.

v
International Standard ISO 8838:2024(en)
Plain bearings — Water-lubricated plain bearing materials
1 Scope
This document specifies requirements for the selection and use of water-lubricated plain bearing materials
used in different equipment and plants under various lubrication conditions, such as
— fluid-film lubrication condition,
— mixed lubrication condition, and
— condition comprising a non-lubrication condition which shifts to a fluid-film lubrication condition.
In addition, this document also specifies requirements for mating (shaft) material, the lubrication method
and for items to consider during the design of water-lubricated plain bearing materials.
The water used as a lubricant is pure water, tap water, river water or seawater. This document does not
apply to the water solution of chemicals, refrigerants, liquid fuels, etc.
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 1043-1, Plastics — Symbols and abbreviated terms — Part 1: Basic polymers and their special characteristics
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 8044, Corrosion of metals and alloys — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1043-1, ISO 4378-1, ISO 4378-2,
ISO 4378-3 and ISO 8044 apply.
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 https:// www .electropedia .org/

4 Plain bearing materials and mating (shafts) materials
4.1 Bearing materials
4.1.1 General
Depending on the equipment, bearings are used in the following lubrication conditions:
a) bearing is constantly immersed in water;
b) there is no lubrication at first and water is supplied after the start of operation;
c) water is forcibly supplied from the beginning.
When required to operate without lubrication, a bearing material with a self-lubricating property shall be
selected. When used in seawater, a bearing material that does not cause galvanic corrosion shall be selected.
NOTE In addition to the materials listed below, the bearing materials listed in ISO 19259 and ISO 20054 are also
used for water-lubricated bearing materials.
4.1.2 Wood-based material
Lignum vitae or materials such as maple and beech impregnated with wax can be used.
Wood-based material has self-lubricating properties.
4.1.3 Carbon-based material
Artificial graphite with or without the following can be used:
a) impregnated resin (phenolic resin, etc.);
b) low melting point metals (such as Cu, Sn, Cu-Sn alloy, etc.).
Carbon-based material has self-lubricating properties, however, there is a risk of galvanic corrosion when
used in seawater.
NOTE Terms related to galvanic corrosion are defined in ISO 8044.
4.1.4 Rubber-based material
Natural rubber (NR) or synthetic rubber, such as chloroprene rubber (CR), acrylonitrile-butadiene rubber
(NBR), and styrene-butadiene rubber (SBR), can be used.
NOTE Other rubber-based materials are defined in ISO 1629.
These rubber-based materials are typically bonded to the inner surface of the metal tube or fibre-reinforced
plastic tube. They are resistant to abrasive wear, however, they do not have self-lubricating properties.
4.1.5 Thermosetting resin-based material
Thermosetting resin such as phenolic resin and unsaturated polyester resin reinforced with fibre or woven
fabric, and, as needed, added with fillers such as graphite, carbon fibre and polytetrafluoroethylene (PTFE)
to improve sliding characteristics can be used.
Thermosetting resin-based material has self-lubricating properties and impact load resistance.

4.1.6 Fluoro resin-based material
Fluoro resin such as PTFE, tetrafluoroethylene-perfluoroalkylvinylether copolymer resin (PFA) and
tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP) added with fillers such as glass fibre and
carbon fibre to improve wear resistance can be used.
Fluoro resin-based material is used as solid type or multilayer type bonded to a metal substrate. It has self-
lubricating properties.
4.1.7 Thermoplastic resin-based material
Thermoplastic resin such as polyamide (PA), polyoxymethylene (POM), polyphenylenesulfide (PPS),
polyetheretherketone (PEEK), polyurethane (PU) and polyethersulfone (PES) added with fillers such as
glass fibre, carbon fibre and PTFE to improve wear resistance and lubricity can be used.
Thermoplastic resin-based material has self-lubricating properties.
4.1.8 Ceramic-based material
Silicon nitride (Si N ), silicon carbide (SiC) or Sialon (Si N -Al O ) can be used.
3 4 3 4 2 3
These ceramic-based materials are resistant to abrasive wear, however, they do not have self-lubricating
properties.
4.1.9 Cermet-based material
Composite materials of ceramics and metals, such as tungsten carbide (WC) based alloy or titanium carbide
(TiC) based alloy, are the most commonly used among cermet-based materials. Cromium carbide (Cr C )
3 2
alloy is used for a coating on a metal substrate.
These cermet-based materials are resistant to abrasive wear, however, they do not have self-lubricating
properties.
4.2 Mating (shaft) materials
4.2.1 General
Lubricating water does not prevent corrosion like oil or grease, so the mating shaft selected shall be
corrosion resistant. A material with high surface hardness, preferably HV 600 or higher and wear resistance
should be selected, in case hard foreign matter, such as sand, enters between sliding surfaces of the bearing
and mating shaft.
However, when using a rubber bearing, the shaft does not need to have a hard surface, because the elastic
deformation of the rubber traps hard foreign matters resulting in less damage to the shaft.
4.2.2 Copper alloy
A bronze sleeve should be fitted on to a steel shaft for marine propulsion shafts.
4.2.3 Stainless steel
Austenitic, martensitic, two-phase precipitation hardening stainless steel, high nitrogen steel or the like
should be used.
NOTE Chemical composition, mechanical properties, etc. of stainless steels ar
...