1. What is ASTM A671 CC65 Class 33 Pipe?
Definition: An electric-fusion-welded (EFW) carbon steel pipe designed for low-temperature and high-pressure service, compliant with ASTM A671 standards.
Grade: CC65 (carbon steel with controlled chemistry: ≤0.30% carbon, ≤1.00% manganese).
Class: 33 (indicates the highest pressure rating among Classes 30-33, typically for cryogenic conditions).
2. Key Material & Mechanical Properties
Tensile Strength: ≥65 ksi (448 MPa).
Impact Testing: Mandatory at -50°F (-45°C) or lower (ensures toughness in extreme cold).
Welding: Longitudinal seams require 100% radiography (RT) or ultrasonic testing (UT).
3. Typical Applications
Oil & Gas: LNG pipelines, cryogenic storage tanks.
Power Plants: High-pressure steam lines in cold climates.
Industrial: Structural supports for Arctic infrastructure.
4. How Does Class 33 Differ from Lower Classes (30-32)?
| Parameter | Class 33 | Class 30-32 |
|---|---|---|
| Design Pressure | Highest (~330 psi) | Lower (~300-320 psi) |
| Impact Test Temp | -50°F or below (strictest) | -20°F to -50°F |
| NDT Requirements | 100% RT/UT + optional PMI | RT/UT may be partial |
5. Testing & Certification Requirements
Hydrostatic Test: 1.5x design pressure for ≥10 seconds.
Certification: Mill Test Reports (MTRs) with full traceability (chemistry, mechanical tests, NDT results).
Optional Tests: Charpy V-notch, hardness, and positive material identification (PMI).
