This standard BS EN 6138:2017 Aerospace series. Cap, protective, non-metallic for fitting ends ≤ 3 000 PSI hydraulic systems is classified in these ICS categories:
49.080 Aerospace fluid systems and components
This European Standard specifies the dimensions, tolerances and required characteristics of protective caps to seal fluid ports during transportation and storage in order to prevent: - contamination by moisture, fluids, chemicals and particles; - spillage inside package or aircraft section; - port and pipe end damages; - port and pipe clogging due to plug ingestion. Because of the cleanliness requirements, parts shall only be used once.