ISO 31657-3:2025

Overview

ISO 31657-3:2025 - Plain bearings - Hydrodynamic plain journal bearings under steady-state conditions - Part 3 specifies characteristic values for the calculation of tilting‑pad journal bearings. It covers selected tilting‑pad designs with four or five pads, either centrally or eccentrically supported, and pad sliding surface angular spans Ω = 80°, 60° and 45°. The data are intended for stationary (steady‑state) operating conditions and support safe hydrodynamic bearing design in accordance with ISO 31657‑1:2025.

Key topics and technical requirements

• Scope of data: Dimensionless characteristic values tabulated and plotted for selected tilting‑pad geometries (Tables 1–56 and Annex A curves).
• Geometry covered: Four‑ and five‑pad tilting‑pad bearings with central/eccentric pivots and specified pad angular spans (Ω = 80°, 60°, 45°).
• Static characteristic values: Includes the Sommerfeld number, relative eccentricity, attitude angle, product of maximum film pressure and Sommerfeld number (pS·o), minimum relative film thickness h*, friction force parameter f*, and lubricant flow‑rate parameters.
• Dynamic characteristic values: Non‑dimensional lubricant film stiffness coefficients (c*) and damping coefficients (d*) for use in rotor‑bearing dynamic analysis.
• Formulas and symbols: Dimensionless parameters and symbols follow ISO 31657‑1:2025 (e.g., So, ε, β). Example formulae (Sommerfeld number, relative eccentricity, film thickness, stiffness/damping scaling) are referenced in the standard.
• Design conditions: Values are calculated for the operating range 0.02 ≤ h ≤ 1 and are valid for stationary operating states under the presumptions and boundary conditions of ISO 31657‑1.
• Application guidance: The standard notes that equivalent calculation procedures are acceptable if they provide comparable numerical solutions.

Applications and who should use it

ISO 31657-3:2025 is aimed at professionals involved in the design, analysis and maintenance of hydrodynamic tilting‑pad journal bearings:

• Mechanical and rotating‑machinery engineers designing bearings for turbines, compressors, generators and pumps
• Bearing manufacturers and OEMs validating pad geometry and performance
• Tribologists and researchers performing bearing performance and stability studies
• Condition‑monitoring and maintenance engineers assessing operating margins and lubrication needs

Use cases include preliminary sizing, dynamic stiffness/damping input for rotor‑bearing models, friction and heat‑generation estimates, and validation of numerical bearing solutions.

Related standards

• ISO 31657‑1:2025 - Calculation of multi‑lobed and tilting‑pad journal bearings (normative reference)
• ISO/TS 31657‑3:2020 - Previous technical specification replaced by this first edition

Keywords: ISO 31657-3:2025, tilting‑pad journal bearings, hydrodynamic plain bearings, characteristic values, Sommerfeld number, film thickness, stiffness, damping, bearing calculation.