ISO 19349:2019 pdf – 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.