1. What is ASTM A671 CC65 Class11 Steel Pipe?
Answer:
ASTM A671 CC65 Class11 is a high-strength electric-fusion-welded (EFW) carbon steel pipe designed for ultra-high-pressure and low-temperature service. The "CC65" indicates a minimum yield strength of 65 ksi (448 MPa), while "Class11" denotes a pressure rating of 11,000 psi (758 bar), making it suitable for critical applications like LNG terminals, offshore risers, and power plant piping.
Key Distinction: Class11 offers ~10% higher pressure capacity than Class10 (10,000 psi), ideal for extreme conditions.
2. What Manufacturing and Testing Standards Apply?
Answer:
Process: EFW with filler metal, 100% radiography (RT) or automated ultrasonic testing (AUT) for weld integrity.
Heat Treatment: Mandatory normalizing or PWHT to refine grain structure and relieve stresses.
Dimensions: Sizes range from 16" to 120" OD, with wall thicknesses per ASME B36.10M.
Critical Note: ASTM A671 pipes are shop-fabricated, unlike field-welded ASTM A672 pipes.
3. What Temperature/Pressure Range Does Class11 Cover?
Answer:
Temperature: -20°F to 650°F (-29°C to 343°C) (with impact testing required below -20°F).
Pressure: 11,000 psi design pressure, suitable for:
Subsea pipelines
High-pressure gas transmission
Cryogenic storage tanks
Safety Margin: Hydrostatic testing at 16,500 psi (1.5x design pressure) ensures reliability.
4. How Does CC65 Class11 Compare to Other Grades?
Answer:
| Grade | Yield Strength (ksi) | Pressure Class | Key Use Case |
|---|---|---|---|
| CA55 | ≥55 | Class62 (6,200 psi) | Moderate pressure |
| CC65 | ≥65 | Class11 (11,000 psi) | Ultra-high pressure |
| CD80 | ≥80 | Class13 (13,000 psi) | Severe environments |
Trade-off: CC65 balances cost and performance but may require corrosion coatings for acidic service.
5. What Certification and Marking Are Required?
Answer:
Testing: RT/UT, hydrostatic tests, and Charpy impact tests (for low temps).
Certification: MTRs must include:
Chemical composition (C, Mn, Si, etc.)
Mechanical properties (tensile, yield, elongation)
Heat treatment records
Marking: Stamped with ASTM A671, CC65, Class11, size, heat no., and manufacturer's logo.
