API 5L vs ASTM A106
API 5L and ASTM A106 are the two most widely specified carbon steel pipe standards in the oil and gas industry. API 5L covers line pipe for pipeline transportation systems. ASTM A106 covers seamless carbon steel pipe for high-temperature service in process plants and power stations. Despite overlapping chemistries for basic grades, the standards differ in scope, testing requirements, grade nomenclature, and permissible manufacturing methods.
Comparison Table
| Feature | API 5L | ASTM A106 |
|---|---|---|
| Issuing body | American Petroleum Institute | ASTM International |
| Scope | Pipeline transportation (liquid and gas) | Seamless pipe for high-temperature service |
| Manufacturing methods | Seamless, ERW, SAW, DSAW | Seamless only |
| Grade system | Gr. A, B, X42, X46, X52…X120 | Gr. A, B, C |
| Product Specification Levels | PSL1 (standard), PSL2 (enhanced) | N/A |
| Yield strength (Gr. B) | 245 MPa min (35.5 ksi) | 240 MPa min (35 ksi) |
| Tensile strength (Gr. B) | 415 MPa min (60 ksi) | 415 MPa min (60 ksi) |
| Carbon max (Gr. B) | 0.26% (seamless) | 0.30% |
| Carbon equivalent | Mandatory for PSL2 | Not specified |
| Impact testing | Mandatory for PSL2 | Optional (Supplementary Requirement S6) |
| NDE of pipe body | UT or hydro (PSL1); UT mandatory (PSL2) | Hydrostatic test mandatory; UT optional |
| Hydrostatic test | Mandatory | Mandatory |
| Sour service (Annex H) | Available for PSL2 | Not available (use supplementary requirements) |
| Fracture toughness | Annex F (DWTT), Annex G (CVN) | Not covered |
| Applicable piping codes | B31.4, B31.8, B31.3 | B31.1, B31.3 |
Key Differences
Pipe types: ASTM A106 is exclusively seamless. API 5L covers seamless, ERW, LSAW, and DSAW pipes, making it the universal line pipe standard for both plant and cross-country pipeline applications.
Testing rigor: API 5L PSL2 mandates tighter chemistry controls, mandatory impact testing, full pipe body NDT, and carbon equivalent limits. ASTM A106 requires these only as supplementary requirements, which must be explicitly called out on the purchase order.
High-strength grades: API 5L grades extend from X42 to X120 (yield strength from 290 to 830 MPa), addressing high-pressure pipeline needs far beyond A106’s maximum Grade C (275 MPa yield). These higher grades use controlled rolling, Q&T, or TMCP (thermomechanical controlled processing) to achieve strength with good toughness.
Sour service: API 5L Annex H (also referenced as ISO 15156/NACE MR0175) provides specific requirements for pipes intended for sour (H2S-containing) environments, including hardness limits, additional testing, and restricted chemistry.
For a detailed overview of carbon steel pipe materials and seamless vs welded pipe types, refer to the full guides.
Leave a Comment
Have a question or feedback? Send us a message.