1. What is ASTM A671 CC60 Class 21?
Definition: High-performance EFW pipe for cryogenic and moderate-pressure service, engineered for industrial and energy applications requiring enhanced strength.
Key Specs:
Yield Strength: 60 ksi (414 MPa) at -20°F (-29°C).
Pressure Rating: 6,000 psi (414 bar) (Class 21).
Material: Carbon steel with impact-tested properties (Charpy V-notch tested).
2. Typical Applications
Oil & Gas:
High-pressure gas transmission pipelines.
LNG terminal cryogenic piping.
Industrial:
High-pressure steam/water systems.
Chemical processing plants (non-corrosive fluids).
3. Material Properties & Testing
| Property | Requirement | Test Standard (ASTM) |
|---|---|---|
| Yield Strength | ≥60 ksi at -20°F (-29°C) | A370 |
| Charpy Impact | ≥20 ft-lb (27 J) at -50°F (-45°C) | A673 (Group 2+) |
| Hydrostatic Test | 1.5x design pressure (9,000 psi) | A671 Section 12 |
| NDT | 100% radiography or ultrasonic | E94 / E213 |
4. Manufacturing & Certification
Process:
Submerged arc welding (SAW) with stringent weld integrity checks.
Post-weld heat treatment (PWHT) mandatory for thickness >1.5".
Certification:
Complies with ASME B31.3, API 5L PSL1, and ISO 3183.
Optional NACE MR0175 for sour service (H₂S environments).
5. Operational Limits & Compliance
Temperature Range: -50°F to 650°F (-45°C to 343°C).
Max Pressure: ≤6,000 psi (414 bar) for Class 21.
Key Standards:
ISO 3183 (Pipeline systems).
ASME B31.8 (Gas transmission pipelines).
