ISO 12131-2:2023

Overview

ISO 12131-2:2023 - "Plain bearings - Hydrodynamic plain thrust pad bearings under steady-state conditions - Part 2: Functions for the calculation of thrust pad bearings" - specifies mathematical functions and supporting data used to calculate the steady-state hydrodynamic performance of oil‑lubricated thrust pad (pad) bearings. The document complements ISO 12131-1 by providing characteristic functions and covers the influence of dynamic viscosity on lubricant film temperature.

Key topics and technical requirements

• Calculation functions for thrust pad bearings, including approximations and auxiliary coefficients for practical use. Functions are provided for:
  • Load carrying capacity (characteristic value F*) as a function of relative bearing width (B/L) and relative minimum film thickness (h_min/C). Range of application quoted: h_min/C = 0.1 to 10.
  • Friction (characteristic value f*) versus B/L and h_min/C.
  • Relative lubricant flow rates (Q1*, Q3*) as functions of B/L and h_min/C.
• Effective dynamic viscosity (η_eff) as a function of effective lubricant film temperature (T_eff). The standard references the Vogel formula for liquids and notes a practical constant (K = 95 °C) for mineral oils; it also links operational viscosity to ISO Viscosity Grade (VG) and provides relations using fluid density.
• Supporting data: tables and figures (e.g., Figures 1–5, Tables 2–5) give numerical values and charts to validate or interpolate results; formulae are approximations of numerically determined curves.
• Normative cross‑reference: ISO 12131-1:2020 (calculation methods and symbol definitions). Bibliography cites Part 3 (guide values) and foundational literature on viscosity-temperature relations.

Applications and who uses it

• Bearing designers and mechanical engineers: to size and validate hydrodynamic thrust pad bearings for machines (pumps, turbines, gearboxes, marine propulsors).
• Tribologists and lubricant specialists: to assess film thickness, friction, and temperature-dependent viscosity effects on bearing performance.
• OEMs and rotating-equipment manufacturers: for product development, specification of bearing geometry and lubricant selection.
• Condition‑monitoring and maintenance engineers: to predict steady-state operating behavior and inform lubrication and cooling strategies.
• CAE and calculation software developers: to implement standardized functions for bearing performance modules.

Related standards

• ISO 12131-1:2020 - Calculation of thrust pad bearings (symbols, boundary conditions, worked examples)
• ISO 12131-3 - Guide values for calculation of thrust pad bearings
• Relevant lubricant standards: ISO VG viscosity grades

Keywords: ISO 12131-2, plain bearings, thrust pad bearings, hydrodynamic, lubricant viscosity, load carrying capacity, friction, lubricant flow rates, ISO VG, bearing calculation.