1. What is A671/CG100 Class 22 Steel Pipe?
Answer:
A671/CG100 Class 22 is an electric-fusion-welded (EFW) steel pipe designed for low-temperature and high-pressure service, complying with ASTM A671 standards. The "CG100" indicates it's made from carbon steel, and "Class 22" specifies its pressure rating and testing requirements (e.g., hydrostatic testing at 100% of specified yield strength).
Key Features:
Material: Carbon steel with controlled chemistry for low-temperature toughness.
Welding: Longitudinal seam welded via electric fusion.
Applications: Cryogenic storage, LNG pipelines, and industrial gas systems.
2. What Are the Temperature and Pressure Limits?
Answer:
Temperature Range: Suitable for -50°F to 650°F (-45°C to 343°C). Class 22 pipes are often used in sub-zero environments due to impact-tested materials.
Pressure Rating: Varies by diameter and wall thickness, but Class 22 typically handles moderate to high pressures (e.g., 1,000–2,000 psi depending on design).
Note: Exact limits depend on the pipe's dimensions and compliance with ASME B31.3/B31.8 codes.
3. How Does A671/CG100 Class 22 Compare to Other Classes (e.g., Class 21 or Class 52)?
Answer:
| Class | Test Pressure | Typical Use Case |
|---|---|---|
| Class 21 | 60% of yield strength | Low-pressure, non-critical systems |
| Class 22 | 100% of yield strength | Moderate/high-pressure, low-temperature |
| Class 52 | 100% + stress-relieved | Severe conditions (e.g., offshore rigs) |
Key Difference: Class 22 offers a balance between cost and performance for cryogenic applications, while Class 52 undergoes additional stress relief for extreme environments.
4. What Standards and Certifications Apply?
Answer:
Primary Standard: ASTM A671 (EFW pipes for atmospheric/lower temps).
Complementary Standards:
ASTM A370 (mechanical testing).
ASME Section IX (welding procedures).
NACE MR0175 (if used in sour service).
Certifications: Mill test reports (MTRs) for chemical composition, hydrostatic tests, and Charpy impact tests at low temps.
5. What Are Common Fabrication and Installation Challenges?
Answer:
Welding: Requires pre/post-weld heat treatment to avoid brittleness in low-temp zones.
Handling: Impact toughness must be preserved; avoid cold bending without evaluation.
Corrosion: Coatings or cathodic protection may be needed for buried pipelines.
Pro Tip: Follow ASTM A671 Appendix X3 for guidance on welding and nondestructive testing (NDT).
