ISO 12:1987 Preview
Aerospace -- Pipelines -- Identification
Lays down die requirements for a scheme to indicate, by appropriate marking, the functions or contents of rigid pipe assemblies in aircraft and spacecraft systems, but excluding those in aero-engines with the exception of those which connect directly to the airframe systems at their break points. These requirements may also be applied to hose assemblies, if desired. The purpose of the scheme is to provide the minimum identification necessary for normal maintenance purposes.