ISO 12131-1:2020

Overview

ISO 12131-1:2020 - Plain bearings: Calculation of hydrodynamic plain thrust pad bearings (steady‑state) defines a calculation method for oil‑lubricated, hydrodynamic plain thrust pad bearings where the thrust collar and bearing surfaces are fully separated by a lubricant film. The standard targets reliable designs for steady‑state conditions (constant load and speed) and covers bearings with incorporated wedge and supporting surfaces. It is intended for the design and optimization of plain thrust bearings used in rotating machinery.

Key topics and technical requirements

• Scope and geometry limits
  • Applies to plain thrust bearings with an incorporated wedge and supporting surface; specifically treats the optimum wedge length ratio lwed/L = 0.75.
  • Allows pad width to length ratios B/L = 0.5 to 2.
  • Calculation method can be applied to other gap shapes (e.g., integrated baffles) provided numerical solutions of the Reynolds equation are available.
• Calculation elements covered
  • Load carrying capacity, frictional power, lubricant flow rate, heat balance, minimum lubricant film thickness and specific bearing load.
  • Detailed calculation procedure addressing loading operations (wear, mechanical and thermal loading), operating conditions and further influencing factors.
  • Numerical solutions of Reynolds equation for finite‑width sliding surfaces are the basis for pressure generation and performance prediction.
• Fundamental assumptions
  • Lubricant is Newtonian, incompressible, with laminar flow and full film lubrication.
  • Lubricant adheres to surfaces, film thickness in radial direction is constant, components are essentially rigid, and inertia/gravity effects of the lubricant are negligible.
  • Boundary conditions: gauge pressure zero at feed, lateral edges and end of pressure field.
• Limitations
  • Restricted to steady‑state operation; dynamic operating conditions (transients, variable speed/load) are excluded.

Practical applications and users

• Primary users: bearing designers, mechanical engineers, OEMs, and tribology specialists working on rotating equipment.
• Typical applications: fans, gear units, pumps, turbines, electrical machines, compressors, machine tools.
• Use cases: design verification, optimization of pad geometry, calculation of frictional heat and lubricant flow, selection of clearances and lubricant properties, and supporting bearing material and cooling decisions.

Related standards

• ISO 12131-2:2016 - Functions for calculation of thrust pad bearings (numerical data/coefficients).
• ISO 12131-3 - Guide values for calculation and safe operation.
• ISO 3448 - Viscosity classification for industrial lubricants.

Keywords: ISO 12131-1:2020, plain bearings, hydrodynamic thrust pad bearings, Reynolds equation, lubricant film thickness, steady‑state bearing design, thrust collar, pad geometry.