ISO 19349:2019

INTERNATIONAL ISO
STANDARD 19349
First edition
2019-03
Plain bearings with liquid
lubrication — Lubricant supply
arrangements and monitoring
Paliers lisses à lubrification fluide — Equipements de graissage et de
surveillance
Reference number
©
ISO 2019
© ISO 2019
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ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Lubrication arrangements . 1
4.1 Self-contained bearings . 1
4.2 Circulated lubrication (forced lubrication) . 1
4.2.1 General. 1
4.2.2 Oil feed and oil return . . . 2
4.2.3 Oil reservoirs . 2
4.3 Hydrostatic lubrication . 3
5 Lubricants . 3
5.1 Suitable lubricants for plain bearings . 3
5.2 Oil cleanliness . 4
6 Lubricant heating . 4
7 Monitoring . 5
7.1 Requirements for design or selection of the lubrication monitoring system . 5
7.2 Requirements for through-life operation of the overall bearing and lubrication system . 5
Bibliography . 6
Foreword
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This document was prepared by Technical Committee ISO/TC 123, Plain bearings, Subcommittee SC 3,
Dimensions, tolerances and construction.
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iv © ISO 2019 – All rights reserved

Introduction
This document is based on German standard DIN 31692-1:1996.
INTERNATIONAL STANDARD ISO 19349:2019(E)
Plain bearings with liquid lubrication — Lubricant supply
arrangements and monitoring
1 Scope
This document provides requirements and guidance on lubricant supply arrangements and monitoring
for liquid-lubricated bearings (plain bearing assemblies) such as those specified in ISO 11687 (all parts).
This document is intended to assist the design of oil-based lubrication systems for hydrodynamic
plain bearings mainly to be used in large-scale rotating machinery for power generation, industry and
transportation.
This document focuses on the most important requirements and characteristics of lubricant supply
arrangements and monitoring for plain bearings. Additional standards such as ISO 10438-1, ISO 10438-2
and ISO 10438-3 would be needed to design complete low-pressure or high-pressure lubrication
systems, along with their corresponding components.
Wherever this document specifies a particular form of solution, whether design or operation, different
solutions can be selected provided they are justified by engineering assessment or reference to similar
systems already in operation.
2 Normative references
There are no normative references in this document.
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 Lubrication arrangements
4.1 Self-contained bearings
The low-pressure lubrication of self-contained bearings is ensured by an internal oil reservoir and a
supply mechanism, driven by the main shaft rotation. Typical self-contained bearing lubrication supply
mechanisms include ring lubrication and viscosity pump lubrication. The lubrication does not require
external energy or equipment. The lubricant does not leave the bearing internal reservoir.
4.2 Circulated lubrication (forced lubrication)
4.2.1 General
The oil supply of forced-lubricated bearings consists of a closed circulation system. The oil supply in
these cases is provided by pumping the lubricant through the bearings. In the supply system, the oil is
pumped out of the reservoir, filtered, cooled and controlled at the desired flow rate or pressure before
being fed to the machine bearings. For this purpose, a complete oil supply system consists of a reservoir,
pumping, filtering, cooling and controlling units. After lubricating the bearings, the oil returns to the
reservoir. Some lube oil units are operated independently of the machine being supplied. Others have
the main lube oil pump being driven by the shaft of the machine.
4.2.2 Oil feed and oil return
To minimize the possibility of vibrations or thermally induced tensile or compressive stresses occurring
in the bearing housing, flexible compensators or connections shall be provided in the oil supply and
drain piping systems if applicable.
For electrically insulated plain bearings, it is necessary to consider whether oil supply and drain pipes
connected to the bearing also need insulating to prevent short circuit of the bearing insulation.
To restrict the pressure losses in the piping system to an economically justifiable amount, the oil mean
flow velocity should not exceed 2 m/s in the supply lines according to experience.
The design of the return fluid flow path from the bearing to the oil reservoir shall be determined by
the technical requirements of the bearing housing and the design requirements of the overall system
installation.
When the return flow is driven by gravity, oil return lines shall have a slope of at least 5 %. According
to ISO 10438-1, oil drains shall be sized to run no more than half full when flowing at normal drain
operating temperature at maximum flow conditions and shall be arranged to ensure good drainage
(recognizing the possibility of foaming conditions). Junctions and changes in the direction of pipes shall
be designed so as not to impair lubricant flow. Sharp bends and down or up loops shall be avoided.
Junctions in return pipes shall be located in the direction of flow. In order to prevent foaming, vertical
slopes exceeding 1 m in length shall be avoided. No devices significantly impeding the flow in the return
line, such as filters, etc. shall be installed.
Where more than one device (bearings, and possibly other consumers) is to be supplied with lubrication
oil, the design of the oil supply and circulation system should mitigate against the potential harmful
interactions in the return lines and oil reservoir caused by differential air pressure conditions.
4.2.3 Oil reservoirs
The basic design requirements for oil reservoirs are given by ISO 4413 in conj
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