ISO 4378-3:2024

Overview

ISO 4378-3:2024 - Plain bearings - Terms, definitions, classification and symbols - Part 3: Lubrication is the fourth edition of the ISO vocabulary for lubrication of plain bearings. It specifies the most commonly used terms, definitions and classifications related to lubrication, provides short forms where unambiguous, and adds an alphabetical index. The document is intended to create a uniform system of designations for lubrication in plain bearings and is applicable more broadly in tribology and machinery components.

Key Topics

• Scope and purpose: Standardizes lubrication terminology for plain bearings to reduce ambiguity in standards, technical literature and engineering communication.
• Types of lubrication (by physical state): gas-film, liquid-film, fluid-film (gas or liquid) and solid-film lubrication.
• Mechanisms of film separation: hydrodynamic, hydrostatic, aerodynamic, aerostatic, boundary, mixed-film (partial-film) lubrication.
• Advanced lubrication models:
  • Elasto-hydrodynamic lubrication (EHL / EHD) - hard EHL, soft EHL, micro EHL.
  • Thermo-hydrodynamic (THL / THD) and thermo-elastohydrodynamic (TEHL / TEHD) explanations (heat and elastic/rheological effects).
• Flow regimes: laminar, transition (Taylor) flow, turbulent flow, starved lubrication and non-lubrication.
• Lubrication methods and delivery: continuous vs periodic; recirculating, life-time prelubrication, once-through systems; application methods such as force-feed, mechanical force-feed, dip-feed (oil-bath), drop-feed (drip), ring lubrication and hand lubrication.
• Lubricant types & properties: classifications by physical state, additives, origin and application; basic lubricant characteristics (viscosity and its pressure/temperature dependence).
• Practical aids: figures illustrating common application methods, short-form terms, and an alphabetical index for quick reference.

Applications

ISO 4378-3:2024 is practical for:

• Bearing designers and mechanical engineers specifying lubrication requirements for plain bearings.
• Maintenance and reliability teams developing lubrication procedures, interval schedules and oil/grease selection.
• Lubricant manufacturers and suppliers aligning product descriptions with standardized terminology.
• Tribologists and researchers using consistent definitions in analysis and reporting.
• Standards bodies and technical writers who draft or harmonize machine and bearing standards.

Using ISO 4378-3 helps ensure clear communication about plain bearings lubrication, reduces misinterpretation, and supports more reliable lubrication design and maintenance practices.

Related standards (if applicable)

• Other parts of the ISO 4378 series (see ISO catalogue for titles and part numbers).
• Standards and resources from ISO/TC 123 (Plain bearings) and general tribology vocabularies (ISO Online Browsing Platform).