1. What is ASTM A671 CG100 Class 50?
Answer:
ASTM A671 CG100 Class 50 refers to electric-fusion-welded (EFW) carbon steel pipes designed for low-temperature and high-pressure service. The designation breaks down as:
CG100: Carbon steel grade with specific chemical composition for cryogenic toughness.
Class 50: Indicates stringent testing requirements, including 100% radiography and higher hydrostatic test pressures compared to lower classes (e.g., Class 22).
Key Standard: ASTM A671 covers EFW pipes for atmospheric and lower-temperature applications.
2. What are the typical applications of Class 50 pipes?
Answer:
These pipes are used in extreme conditions requiring high strength and low-temperature resilience, such as:
LNG (Liquefied Natural Gas) pipelines (operating below -45°F/-43°C).
Cryogenic storage tanks and refrigeration systems.
Offshore oil/gas platforms where pressure and corrosion resistance are critical.
3. How does Class 50 differ from Class 22 in ASTM A671?
Answer:
| Parameter | Class 50 | Class 22 |
|---|---|---|
| Testing | 100% radiography + higher hydrotest | 100% radiography (lower pressure) |
| Pressure Rating | Higher (suitable for severe service) | Moderate |
| Applications | Extreme low-temp/pressure | Standard low-temp |
Note: Class 50 is more rigorous in quality control and performance thresholds.
4. What are the mechanical properties of CG100 material?
Answer:
Yield Strength: ≥ 60 ksi (414 MPa).
Tensile Strength: 85–110 ksi (586–758 MPa).
Impact Test: Charpy V-notch at -50°F (-45°C) to ensure ductility in cryogenic conditions.
Chemical Composition: Controlled carbon (≤0.30%), manganese, and silicon for weldability and toughness.
5. What are the fabrication and certification requirements?
Answer:
Welding: Submerged arc welding (SAW) or similar, with PWHT (Post-Weld Heat Treatment) if thickness exceeds limits.
Inspection: Mandatory 100% radiographic examination and hydrostatic testing per ASTM A671.
Certification: Mill Test Reports (MTRs) must verify compliance with chemical, mechanical, and non-destructive testing (NDT) criteria.
