ISO 7902-1:2026

Overview

ISO 7902-1:2026 is an international standard published by ISO, providing a comprehensive calculation procedure for oil-lubricated hydrodynamic plain journal bearings under steady-state operating conditions. This document specifically addresses circular cylindrical bearings with angular spans of 360°, 180°, 150°, 120°, and 90°, commonly used in machines where the load is centrally applied to the arc segment. The standard defines precise methods for designing plain bearings to ensure reliable operation, focusing on situations where the shaft and bearing surfaces are fully separated by a lubricant film. Key applications include turbines, generators, electric motors, gear units, rolling mills, and pumps.

The procedure outlined in ISO 7902-1:2026 is relevant when the magnitude and direction of the applied load and the rotational speed are constant, making it suitable for equipment in steady-state operation. It is not intended for use in applications where dynamic or time-varying loads, such as those resulting from vibrations or rotor instabilities, are present.

Key Topics

• Calculation Methodology: Specifies the use of Reynolds equation for determining pressure distributions within the bearing’s lubricant film under finite length conditions.
• Assumptions and Preconditions:
  • Lubricant is Newtonian and incompressible.
  • Flow is laminar and adheres fully to sliding surfaces.
  • Clearance geometry between shaft and bearing remains constant, excluding negligible deformations.
• Boundary Conditions: Defines how lubricant film pressure starts and dissipates across loaded and unloaded zones within the bearing.
• Determining Key Parameters: Guidance on calculating load-carrying capacity (using the Sommerfeld number), frictional losses, lubricant flow rate, and the bearing heat balance.
• Limits and Influences:
  • Clearly states permissible operational parameters such as minimum lubricant film thickness and specific bearing load.
  • Discusses mechanical and thermal limits, effects of geometry, material strength, lubrication quality, and operational safety margins.
• Practical Considerations: Outlines methods for verifying calculation accuracy, including iterative procedures and recommendations for optimizing bearing parameters.

Applications

ISO 7902-1:2026 is fundamental for engineers and designers working with hydrodynamic plain journal bearings in steady-state conditions. It is widely applied in the design and analysis of bearings for:

• Turbines and Generators: Ensures reliability and thermal management in high-speed rotating machinery.
• Electric Motors and Gear Units: Optimizes size and reduces wear for efficient, long-lasting operation.
• Rolling Mills and Pumps: Addresses heavy load and continuous duty requirements typical in industrial machinery.
• General Rotating Equipment: Any application where reliable oil-lubricated bearings are critical under steady, predictable loading and speed.

The standard aids in optimizing bearing geometry, verifying heat dissipation needs, and confirming that operation remains within safe limits to prevent wear, overheating, and premature failure.

Related Standards

• ISO 7902-2: Details the functions and mathematical relationships used in the calculation procedures presented in ISO 7902-1.
• ISO 7902-3: Specifies permissible operational parameters to ensure the proper functioning and reliability of hydrodynamic plain journal bearings.
• Other ISO/IEC Standards: Relevant for bearing terminology, material compatibility, and lubrication methods.

By following ISO 7902-1:2026 and its related standards, users ensure best practices in the design and optimization of circular cylindrical hydrodynamic plain journal bearings, contributing to machinery safety, efficiency, and longevity.

Keywords: ISO 7902-1:2026, hydrodynamic bearings, plain journal bearings, calculation procedure, oil-lubricated bearings, steady-state conditions, bearing design, machinery reliability, load-carrying capacity, lubricant film, heat balance.