1. What is ASTM A671 CH115 Class 20 Steel Pipe?
Answer:
ASTM A671 CH115 Class 20 is an electric-fusion-welded (EFW) steel pipe designed for low-temperature and high-pressure service. The "CH115" denotes a carbon-manganese-silicon steel grade with enhanced strength, while "Class 20" indicates a hydrostatic test pressure of 200 psi (higher than Class 22). These pipes are used in cryogenic, power, and petrochemical industries.
2. Key Material Properties and Composition?
Answer:
Material: CH115 grade (C-Mn-Si steel) with higher tensile strength than CG100.
Tensile Strength: ≥70 ksi (483 MPa).
Impact Toughness: Required for sub-zero temperatures (e.g., -50°F/-45°C).
Welding: EFW process with 100% radiography for seam integrity.
3. Typical Applications of CH115 Class 20 Pipes?
Answer:
Cryogenic systems (LNG, liquid oxygen pipelines).
Power plants (high-pressure steam lines, boiler components).
Oil & gas (refinery piping, sour service if compliant with NACE MR0175).
Industrial processes requiring ductility at low temperatures.
4. How Does Class 20 Differ from Other A671 Classes?
Answer:
Pressure Rating: Class 20 is tested at 200 psi (vs. Class 22's 100 psi).
Thickness: Generally thicker than lower classes (e.g., Class 12).
Testing: Mandates hydrostatic + optional nondestructive exams (e.g., UT, RT).
5. Governing Standards and Certifications?
Answer:
Primary Standard: ASTM A671 (EFW pipes for low-temp service).
Testing Standards: ASTM A370 (mechanical), ASTM A435 (radiographic).
Design Codes: ASME B31.3 (process piping).
Optional: NACE MR0175 for corrosive environments.
