1. What is ASTM A671 CC70 Class 23 Steel Pipe?
Answer:
ASTM A671 CC70 Class 23 is an electric-fusion-welded (EFW) carbon steel pipe designed for low-temperature service (down to -70°F/-57°C). Key specifications:
CC70: Material grade requiring Charpy V-notch impact testing at -70°F to ensure fracture resistance.
Class 23: Minimum yield strength of 23 ksi (159 MPa), ideal for moderate-pressure cryogenic applications.
Typical Use: LNG pipelines, chemical processing, and subzero industrial systems.
2. How is it manufactured and quality-controlled?
Answer:
Welding Process: EFW with filler metal, subjected to 100% radiographic examination (RT) for weld integrity.
Heat Treatment: Stress-relieved or normalized to enhance low-temperature toughness.
Testing: Mandatory Charpy impact tests at -70°F, hydrostatic tests, and chemical composition verification per ASTM A671.
3. How does Class 23 differ from Class 22 or Class 72?
Answer:
| Parameter | CC70 Class 23 | CC70 Class 22 | CC65 Class 72 |
|---|---|---|---|
| Yield Strength | 23 ksi (159 MPa) | 22 ksi (152 MPa) | 72 ksi (500 MPa) |
| Application | Moderate-pressure cryogenic | Low-pressure cryogenic | High-strength cryogenic |
4. What are standard dimensions and tolerances?
Answer:
Diameter Range: 16" to 120" OD (common for large-scale cryogenic pipelines).
Wall Thickness: Complies with ASTM A671 tolerances (±10% nominal thickness).
Length: Standard 40ft (12.2m), with custom lengths available.
5. What corrosion protections are recommended?
Answer:
External: 3LPE coating or cathodic protection for buried pipelines.
Internal: Epoxy/FBE linings for chemical resistance in aggressive media.
Maintenance: Regular inspection for weld and coating integrity in cryogenic environments.
