1. What is ASTM A671 CC70 Class 60 Steel Pipe?
Answer:
ASTM A671 CC70 Class 60 is an electric-fusion-welded (EFW) carbon steel pipe engineered for ultra-low-temperature service (down to -70°F/-57°C). Key specifications:
CC70: Material grade requiring Charpy V-notch impact testing at -70°F to validate cryogenic toughness.
Class 60: Minimum yield strength of 60 ksi (414 MPa), designed for extreme-pressure cryogenic systems (e.g., LNG storage tanks, high-pressure gas transmission).
2. What are the manufacturing and quality control standards?
Answer:
Welding Process: EFW with filler metal, 100% radiographic (RT) or ultrasonic (UT) inspection for weld integrity.
Heat Treatment: Stress-relieved or normalized to meet low-temperature ductility requirements.
Testing:
Mandatory Charpy impact tests at -70°F.
Hydrostatic pressure test at 1.5x design pressure.
Chemical composition verification (e.g., C ≤ 0.25%, Mn ≤ 1.40%).
3. How does Class 60 compare to other ASTM A671 classes?
Answer:
| Parameter | CC70 Class 60 | CC70 Class 22 | CC65 Class 72 |
|---|---|---|---|
| Yield Strength | 60 ksi (414 MPa) | 22 ksi (152 MPa) | 72 ksi (500 MPa) |
| Application | Extreme-pressure cryogenic | Low-pressure storage | Ultra-high-strength |
| Cost | Premium for critical uses | Budget-friendly | Specialized high-cost |
4. What are standard dimensions and tolerances?
Answer:
Diameter: 16"–120" OD (standard for large-scale cryogenic pipelines).
Wall Thickness: Tolerance ±10% nominal thickness per ASTM A671.
Length: Typically 40ft (12.2m), with custom lengths up to 60ft available.
5. How to ensure corrosion protection and operational safety?
Answer:
External Protection:
3LPE coating (3-layer polyethylene) for buried/submerged pipelines.
Cathodic protection in corrosive environments (e.g., coastal/industrial areas).
Internal Protection:
Epoxy/FBE linings for chemical resistance (e.g., acidic LNG contaminants).
Maintenance: Annual inspections of welds and coatings in cyclic pressure/temperature conditions.
