Overview
ISO 19631:2015 - Aerospace series - Tube fittings for fluid systems, 5 080 psi (35 000 kPa) - Qualification specification - defines performance and quality requirements for the qualification and manufacture of tube fittings used in aircraft hydraulic systems rated to 5 080 psi (35 000 kPa). The standard establishes baseline design, material, environmental and test criteria to ensure reliable performance of separable and permanent fittings (dash sizes –04 to –20) used in high‑performance aerospace hydraulic systems.
Key topics and technical requirements
- Scope and applicability: Covers separable/permanent pipe end fittings, permanent connection fittings and separable connection fittings for sizes –04 to –20; temperature and pressure classes per ISO 6771.
- Materials: Acceptable materials include titanium alloys and corrosion‑resistant steels (with equivalent materials allowed if they pass specified tests). Magnesium is explicitly excluded.
- Environmental limits: Ambient and hydraulic fluid temperature range typically −54 °C to +135 °C.
- Pressure ratings: Design operating pressure (DOP) = 35 000 kPa (5 080 psi); proof pressure = 2 × DOP; burst/ultimate pressure = 3 × DOP.
- Qualification and manufacture: Requires both manufacturer qualification and product qualification by purchaser or approved outside agency; assemblies must be manufactured to the same dimensions, materials and processes as qualified test articles.
- Test and performance regime: Extensive testing requirements including:
- Proof pressure and gaseous pressure leakage tests (per ISO 10583)
- Hydraulic impulse resistance: 300 000 cycles at 150% of DOP (≈52 500 kPa / ~7 620 psi) over specified temperatures
- Flexure fatigue, tensile load capability, thermal shock, over‑tightening, salt spray, vibration, fire, system pressure test, fuel and hydraulic fluid ageing, stress corrosion, lightning strike, re‑use capability, and more (see clauses 3.5.1–3.5.21).
- Manufacturing tolerances and design: Requirements for fluid passages, alignment, and allowable offsets when drilled; passage clearance and angular misalignment limits specified.
Applications and users
- Who uses ISO 19631:2015: Aerospace OEMs, hydraulic component manufacturers, suppliers of tube fittings, maintenance/repair/overhaul (MRO) organizations, qualification and test laboratories, and procurement/specification engineers.
- Practical value: Ensures fittings and tube/fitting assemblies meet rigorous safety and reliability criteria for high‑pressure aircraft hydraulic applications - reducing leak risk, improving durability under impulse and thermal cycling, and providing a documented basis for supplier qualification and acceptance testing.
Related standards
- ISO 6771 (temperature and pressure classes)
- ISO 6772, ISO 6773 (impulse and thermal shock testing)
- ISO 10583 (tube/fitting test methods)
- ISO 7257, ISO 7137 (related environmental and fatigue tests)
- EUROCAE ED‑14E / RTCA DO‑160E, Section 22 (lightning induced transient susceptibility)
Keywords: ISO 19631:2015, tube fittings, aerospace, hydraulic systems, 5 080 psi, qualification specification, pressure testing, hydraulic impulse resistance, manufacturer qualification.