What alloy specifications meet international standards for compressed gas storage?
ASME-approved 5083-O alloy remains the baseline with 270MPa minimum tensile strength for Type I tanks. ISO 9809-3 requires 0.2% proof stress ≥215MPa for CNG vessels. Modified 5456-H116 alloy now dominates hydrogen tanks with 15% improved stress corrosion resistance. European EN 14286 mandates ≤0.25% iron content to prevent intergranular cracking. Emerging Al-Mg-Sc alloys (0.2% Sc addition) demonstrate 30% higher fatigue life at 300-bar cyclic pressure.
How are aluminum gas tank plates tested for weld integrity?
Radiographic testing (RT) detects internal flaws at 2% sensitivity per ASME Section V. Penetrant testing (PT) verifies 0.1mm surface cracks after stress relief at 250°C for 1 hour. Burst testing at 2.5× working pressure (typically 550 bar for H₂ tanks) confirms safety margins. Microhardness mapping ensures HAZ remains below 120HV for 5xxx series alloys. Eddy current arrays now automate 100% seam inspection at 2m/minute scan rates.
What corrosion protection systems are mandatory for LPG/CNG applications?
Internal polymer liners (0.5-1.2mm thick) prevent sulfide stress cracking in wet H₂S environments. External epoxy-polyurethane hybrid coatings withstand 1000h salt spray per NACE TM0304. Sacrificial anode tabs (Zn or Mg) protect submerged portions in marine CNG carriers. Laser-cleaned surfaces must achieve Sa 2.5 cleanliness before coating. Novel graphene-enhanced primers reduce cathodic disbondment by 60% in field tests.
How does cryogenic performance affect aluminum selection for LNG tanks?
5083-O alloy maintains 25J Charpy impact energy at -196°C for primary containment. Special grain-refined 5052-H32 prevents brittle fracture with ≤50μm grain size. Thermal contraction coefficients must match 9% nickel steel supports (23.6×10⁻⁶/°C at -160°C). Leak-before-break design requires K₁₀ fracture toughness >29MPa√m. Multi-layer vacuum-insulated panels now integrate aluminum foil barriers with 0.004W/m·K thermal conductivity.
What innovations improve aluminum tank recyclability per 2025 regulations?
Dissimilar material joints now use friction stir welding for contamination-free recycling. Color-coded alloy tags (laser-engraved QR codes) enable automated sorting. Closed-loop recycling achieves 98.7% material recovery in Airbus A380 tank refurbishment. Blockchain-tracked recycled content qualifies for EU Emission Trading System credits. Hydrogen-compatible alloys are being standardized under new ISO 19888:2025 for circular economy compliance.
