ISO 31657-1:2025

Overview

ISO 31657-1:2025 - Plain bearings - Hydrodynamic plain journal bearings under steady-state conditions - Part 1: Calculation of multi-lobed and tilting pad journal bearings provides an easy-to-use, standardized calculation procedure for the design and optimisation of oil-lubricated hydrodynamic plain journal bearings. The standard focuses on multi-lobed (2, 3, 4 lobes) and symmetrically loaded tilting-pad (4, 5 pads) journal bearings operating in steady-state conditions. It is intended to predict bearing performance where complete film separation exists and where operating parameters remain constant.

Key topics and technical requirements

• Calculation method: A simplified numerical procedure (with defined assumptions and preconditions) for estimating bearing performance without recourse to full CFD or advanced elastohydrodynamic models.
• Hydrodynamic performance parameters: Procedures to calculate load-carrying capacity, frictional power, lubricant flow rates, heat balance, and maximum lubricant film temperature and pressure.
• Geometrical and operating limits: Guidance for typical use up to journal circumferential speeds of approximately 90 m/s and practical applicability when specific load × speed (p·U) does not exceed about 200 MPa·m/s.
• Bearing types covered: Multi-lobed journal bearings with laterally closed lubrication pockets and symmetrically loaded tilting-pad journal bearings. The method can be extended to similar gap forms if numeric solutions exist.
• Steady-state restriction: The standard explicitly excludes unsteady or transient operating states; it assumes constant load magnitude/direction and constant rotor speed.
• Stiffness and damping: Reference to characteristic values and linear vibration parameters provided in ISO 31657-2 and ISO 31657-3 (stiffness and damping coefficients for vibration and stability studies).
• Documentation elements: Definitions, symbols and units (comprehensive symbol table), calculation steps, and informative Annex A with worked examples.

Practical applications and users

ISO 31657-1:2025 is directly useful for:

• Bearing designers and tribologists performing preliminary design and optimisation of plain bearings.
• Rotating-equipment engineers working on turbines, compressors, generators, electric motors, gearboxes and pumps.
• Maintenance and reliability engineers evaluating bearing operating conditions (temperature, pressure, flow, friction).
• Engineering consultants and academics needing a standardized, reproducible calculation method for design checks and comparative studies.

Practical benefits include quicker design iterations, standardized checks for allowable loads and temperatures, and a common technical language for industry suppliers and OEMs.

Related standards

• ISO 31657-2: Characteristic values for multi-lobed journal bearings
• ISO 31657-3: Characteristic values for tilting-pad journal bearings
• ISO 31657-4: Permissible operational parameters for calculation of multi-lobed and tilting pad journal bearings
• ISO 7902 series: Calculation methods for circular cylindrical bearings (lower speed range)

Keywords: ISO 31657-1:2025, plain bearings, hydrodynamic plain journal bearings, multi-lobed bearings, tilting-pad bearings, bearing calculation, steady-state bearings, bearing design, turbine bearings.