ISO 12:1987

Overview

ISO 12:1987 - Aerospace - Pipelines - Identification defines a minimum, standardized scheme for marking rigid pipe assemblies in aircraft and spacecraft systems to show their function or contents. The standard excludes pipelines mounted on aero-engines except where they connect directly to the airframe at break points, and it may also be applied to hose assemblies if desired. The primary objective is to provide the minimum identification needed for normal maintenance, safe handling and correct servicing.

Key topics and technical requirements

• Scope and purpose: Identification of pipeline function/content to support maintenance, safety and logistics; applies to onboard aircraft and spacecraft systems (engine exclusions noted).
• Fundamental identification mark:
  • Minimum width: 25 mm.
  • Includes a symbol band (approx. 7 mm) and repeated circuit designation in letters (minimum 3 mm high).
  • Standard symbols and descriptions are listed in a table (e.g., fuel, hydraulic control, oxygen, cooling, etc.).
• Supplementary identification:
  • For more detailed subdivision (specific functions or contents), additional narrow marks or wording may be used adjacent to the fundamental mark.
  • Supplementary marks must be at least 12 mm wide and use letters of at least 2 mm height when textual.
• Symbols, colors and warnings:
  • Standardized pictograms and patterns are defined for common fluids and systems (see symbol table and figure references in the standard).
  • A skull (warning) symbol is specified to mark pipelines whose contents are hazardous to maintenance personnel.
  • Color coding: permitted, with chromaticity and luminance values defined in a color table; colors must not impair inscription visibility or damage pipe materials.
• Legibility & temperature considerations:
  • Where high operating temperatures prevent standard markings, a minimum black-letter inscription (applied per marking location rules) must remain legible.
• Placement:
  • Marks should be applied at both ends of a pipe and at intervals ensuring at least one mark is visible from any observation point; always near couplings and access panels.
• Procurement & traceability:
  • Identification marks should include the national standard number and the symbol number for supply/manufacture traceability.

Applications and practical value

• Ensures consistent pipeline identification across aircraft and spacecraft for:
  • Routine maintenance and inspections
  • Troubleshooting and repair operations
  • Safe handling of hazardous fluids
  • Parts procurement and logistics
• Useful in line maintenance, overhaul shops, OEM production, aerospace integrators and certification documentation.

Who should use ISO 12:1987

• Aerospace engineers and designers specifying piping/hose identification
• Maintenance, repair and overhaul (MRO) personnel
• Technical publications and OEMs creating maintenance manuals
• Quality, safety and compliance teams in aviation and space organizations

Related standards

• ISO 3323 - referenced for hydraulic fluid type identification and color coding; consult the latest edition when specifying hydraulic fluid marking.

Keywords: ISO 12:1987, aerospace pipeline identification, aircraft pipe marking, pipeline identification standard, rigid pipe assemblies, hose assemblies, maintenance marking.