ISO 7146-2:2019

Overview

ISO 7146-2:2019 - Plain bearings: Appearance and characterization of damage to metallic hydrodynamic bearings - Part 2: Cavitation erosion and its countermeasures - defines, describes and classifies the characteristic forms of cavitation erosion seen in metallic hydrodynamic plain bearings and presents possible countermeasures. The standard is focused on damage with a well-defined appearance that can be attributed to specific causes with a high degree of certainty. Photographs and diagrams illustrate typical damage forms.

Key topics

• Mechanism of cavitation erosion: bubble formation and implosion, local high pressures/temperatures, surface roughening, crack initiation and particle wash-out.
• Classification of cavitation erosion: five types by mechanism - Type 1 Flow, Type 2 Impact, Type 3 Suction, Type 4 Discharge, Type 5 Miscellaneous.
• Factors influencing occurrence: journal speed, bearing load and dynamic load patterns, journal motion and vibration, bearing clearance and geometry, oil supply pressure and properties (viscosity, vapor pressure, temperature), contamination (air, water, particles), and bearing material properties (hardness, toughness, fatigue strength).
• Appearance-based diagnosis: guidance to identify cavitation damage from surface texture, pores, cracking and polished versus rough pockets; emphasis that appearance alone may be insufficient and operating history is essential.
• Countermeasures: general and type-specific measures such as modifying oil flow to be continuous and smooth, avoiding sharp edges (use chamfers/radii), optimizing oil supply and geometry of oil holes/grooves, and material or lubrication changes. (Illustrations provide examples for each cavitation type.)

Applications

• Failure analysis and root-cause investigations of plain bearing damage.
• Design reviews for journal and hydrodynamic bearings to reduce cavitation risk.
• Maintenance and inspection procedures - interpreting observed damage and selecting corrective actions.
• Tribology research, OEM engine and rotating-equipment manufacturers, powertrain and industrial bearing engineers.
  Use the standard to correlate observed surface damage with likely mechanisms and to identify practical countermeasures for design, lubrication and maintenance changes.

Who should use this standard

• Bearing designers and OEMs
• Maintenance, reliability and condition‑monitoring engineers
• Tribologists and failure analysts
• Engine manufacturers and rotating‑machinery engineers
• Standards and testing organizations

Related standards

ISO 7146-1 (General guidance on appearance and characterization of bearing damage) and ISO 4378 series (plain bearing terminology, friction, wear and lubrication) are referenced and complementary.

Keywords: ISO 7146-2:2019, cavitation erosion, plain bearings, hydrodynamic bearings, metallic bearings, bearing damage, countermeasures, journal bearings, failure analysis, lubrication.