ISO/TR 11340:1994

Overview

ISO/TR 11340:1994 is a Type 3 ISO Technical Report that provides a uniform guide for defining the degree of external leakage from hydraulic hose assemblies. The classification is intended to be determined by visual means rather than instrumentation and records the observed leakage state at the time of inspection, recognising that the condition may change over time. This guidance was developed under ISO/TC 45/SC 1 (Elastomers and hose assemblies).

Key Topics

• Purpose and scope: Establishes a simple, repeatable visual scale for external leakage on hydraulic systems and hose assemblies.
• Visual classification: A six-level class system (Classes 0–5) describes leakage by appearance and behaviour at observation time:
  • Class 0: No indication of moisture
  • Class 1: Non-recurrent fluid (isolated, non-continuous wetting)
  • Class 2: Recurrent fluid that does not form a drop
  • Class 3: Recurrent fluid forming a drop that does not fall
  • Class 4: Recurrent fluid where drops form and fall
  • Class 5: Recurrent fluid where drop frequency creates a measurable flow
• Observation emphasis: The classification reflects the instantaneous state seen by an inspector and notes that leakage may vary over time (e.g., intermittent leaks, pressure-dependent behaviour).

Applications

This report is practical for organizations and personnel involved in hydraulic system maintenance, inspection and safety management. Typical uses include:

• Maintenance planning: Prioritise repairs by class to manage risk and downtime.
• Routine inspection: Standardise visual checks across teams and sites to improve consistency.
• Safety management: Identify and track leak severity to reduce slip, contamination and fire hazards.
• Quality control and commissioning: Use the classification as part of acceptance checks for hose installations.

Benefits:

• Provides a clear, easy-to-apply visual scale for field inspections
• Improves comparability of inspection records across teams and time
• Supports safer, more predictable maintenance decisions

Related Standards

This technical report complements broader ISO work on elastomers, hoses and hydraulic assemblies (ISO/TC 45/SC 1). Users should apply ISO/TR 11340:1994 alongside any applicable standards for hose design, assembly, pressure testing and materials to form a complete inspection and maintenance regime.

For implementation, integrate the visual classes into inspection forms, maintenance logs and staff training to ensure consistent application and clearer tracking of external leakage in hydraulic systems.