What Is A671 CJA115 Class 32 Pipe?
ASTM A671 CJA115 Class 32 is an electric-fusion-welded carbon steel pipe designed for low-temperature and high-pressure service. The pipe is manufactured from pressure-vessel-quality plate: the plate is formed into a cylinder and the longitudinal seam is welded with filler metal added during the electric fusion welding process. The designation CJA115 identifies the material grade, commonly cross-referenced with ASTM A537 Class 1 for chemistry and mechanical properties, and Class 32 defines a stress-relieved manufacturing condition combined with impact testing of the finished pipe.
Material Grade CJA115
The CJA115 grade is a normalized carbon-manganese steel with controlled composition, developed for subzero-temperature service. Carbon is limited to about 0.24 percent and manganese ranges from 0.70 to 1.35 percent, which gives the steel good weldability and toughness. The steel is heat treated and verified by Charpy impact testing at the specified service temperature, and the normalized structure provides the fine grain size required for low-temperature ductility.
| Property | Typical Requirement |
|---|---|
| Minimum yield strength | 50 ksi, equal to 345 MPa |
| Tensile strength | 70 ksi to 90 ksi range, equal to 485 to 620 MPa |
| Impact testing | Charpy V-notch at low temperature |
| Carbon, maximum | About 0.24% |
| Manganese | 0.70% to 1.35% |
What Class 32 Means
In the ASTM A671 class system, the class number defines the manufacturing and testing condition of the pipe. Class 32 combines the stress-relieved heat treatment with impact testing, which provides additional assurance beyond the examination of the weld alone. Stress relief reduces residual welding stresses, and the impact test verifies that the finished pipe retains toughness at the design temperature. This combination is selected for the most critical low-temperature services.
Manufacturing and Testing Sequence
The plate is formed into a cylinder and the longitudinal seam is welded with filler metal. The pipe is then heat treated, with stress relief applied to the weld and surrounding material. Non-destructive examination of the weld, hydrostatic testing, tensile testing, and Charpy impact testing at the specified temperature complete the verification. All results are documented in the mill test report.
Typical Applications
A671 CJA115 Class 32 pipe is used in LNG terminals and liquefaction plants, cryogenic storage and transport systems, and high-pressure gas lines in cold climates. The petrochemical industry specifies it for low-temperature process piping, and offshore platforms use it for utility and process lines where subzero temperatures and high pressures occur. The stress-relieved, impact-tested condition gives the pipe a complete quality record for the most demanding service.
FAQ
What does Class 32 add over Class 30?
Class 32 adds stress relief and impact testing of the finished pipe to the examination requirements of the class system. This provides additional assurance of toughness and low residual stress for critical low-temperature service.
Why is stress relief important for low-temperature pipe?
Welding leaves residual stresses in the seam area. Stress relief reduces these stresses, lowering the risk of brittle fracture at low temperature and improving the dimensional stability of the pipe in service.
Is CJA115 suitable for offshore use?
Yes. The combination of verified low-temperature toughness, full examination, and hydrostatic testing makes the grade suitable for offshore platforms, subject to the project specification and design code.
What is the impact test temperature?
The Charpy V-notch impact test is performed at the temperature specified for the service, typically the minimum design metal temperature of the system, and the acceptance values follow the applicable standard edition.
Can this pipe be welded in the field?
Yes. Field girth welds are made with qualified procedures and appropriate consumables, and the joints are examined and documented per the project specification.
What documents are supplied?
Mill test reports document the chemical composition, tensile and impact properties, heat treatment, stress relief, non-destructive examination, and hydrostatic test results.
