1. What is ASTM A671 CB70 Class 22?
Standard: ASTM A671 ultra-high-pressure cryogenic EFW pipes for extreme industrial and subsea applications.
Key Specifications:
70 ksi (483 MPa) minimum yield strength at -50°F (-45°C).
Design Pressure: Up to 7,250 psi (500 bar) (Class 22 rating).
Material: Carbon-manganese steel with micro-alloying (Nb/V/Ti) + Ni/Cr for enhanced corrosion resistance.
2. Applications
Oil & Gas:
Deepwater subsea pipelines (≥3,000m depth).
High-pressure gas injection systems (LNG plants).
Industrial:
Cryogenic hypercompressors (-50°F to 750°F).
Nuclear/power plant high-pressure coolant lines.
3. Material Properties & Testing
| Property | Requirement | Test Standard |
|---|---|---|
| Yield Strength | ≥70 ksi at -50°F (-45°C) | ASTM A370 |
| Impact Toughness | ≥30 ft-lb (41 J) at -50°F | ASTM A673 (Charpy V-notch) |
| Hydrostatic Test | 4.5x design pressure (per Class 22) | ASTM A671 Section 12 |
| NDT (UT/RT/MT/PT) | 100% weld + base metal inspection | ASTM E317/E94/E709/E1417 |
4. Manufacturing & Certification
Process:
Electric fusion welding with PWHT + Q&T (Quench & Temper).
Thermomechanical controlled processing (TMCP) for grain refinement.
Certification:
Complies with ASME B31.3, API 5L PSL2, and DNV-OS-F101.
Third-party validation (e.g., Lloyds, Bureau Veritas) mandatory for subsea use.
5. Operational Limits & Compliance
Temperature Range: -50°F to 800°F (-45°C to 427°C).
Pressure Limit: ≤7,250 psi (500 bar) for Class 22.
Key Standards:
ASME Section VIII Div. 3 (Alternative Pressure Vessels).
ISO 3183:2019 (Pipeline applications).
