1. What is ASTM A671 CD80 Class 20 Steel Pipe?
Answer:
ASTM A671 CD80 Class 20 is an electric-fusion-welded (EFW) carbon steel pipe designed for low-temperature service (down to -80°F/-62°C). Key specifications:
CD80: Material grade requiring Charpy V-notch impact testing at -80°F to ensure cryogenic toughness.
Class 20: Minimum yield strength of 20 ksi (138 MPa), suitable for moderate-pressure cryogenic systems (e.g., liquid natural gas (LNG) auxiliary lines, industrial gas storage).
2. What are the manufacturing and certification requirements?
Answer:
Welding: EFW process with filler metal, 100% radiography (RT) or ultrasonic testing (UT) for weld integrity.
Heat Treatment: Stress-relieved or normalized to enhance low-temperature ductility.
Certification: Mill test reports (MTRs) must include:
Chemical composition (e.g., C ≤ 0.30%, Mn ≤ 1.40%).
Mechanical properties (yield strength ≥ 20 ksi, tensile strength 55–75 ksi).
Impact test results at -80°F (minimum 20 ft-lb average energy absorption).
3. How does Class 20 compare to other ASTM A671 classes?
Answer:
| Parameter | CD80 Class 20 | CD80 Class 10 | CD80 Class 60 |
|---|---|---|---|
| Yield Strength | 20 ksi (138 MPa) | 10 ksi (69 MPa) | 60 ksi (414 MPa) |
| Application | Moderate-pressure cryogenic | Low-pressure | High-pressure cryogenic |
| Cost | Mid-range | Low | Premium |
4. What are standard dimensions and tolerances?
Answer:
Diameter: 16"–120" OD (standard for industrial pipelines).
Wall Thickness: Tolerance ±10% nominal thickness (per ASTM A671).
Length: Typically 40ft (12.2m), customizable up to 60ft.
5. How to ensure corrosion protection and longevity?
Answer:
External:
3LPE coating (3-layer polyethylene) for buried/submerged pipelines.
Cathodic protection in corrosive environments (e.g., coastal areas).
Internal:
Epoxy/FBE linings for chemical resistance (e.g., LNG contaminants).
Maintenance: Annual inspections of welds and coatings in cyclic service.
