API 5L vs ASTM A106: Line Pipe Selection
API 5L and ASTM A106 are the two primary specifications for carbon steel pipe used in the oil and gas industry. API 5L covers line pipe for pipeline transportation systems, while ASTM A106 covers seamless carbon steel pipe for high-temperature service in process piping. Choosing between API 5L vs ASTM A106 depends on the application, design code, and operating conditions.
Both specifications produce pipes that appear physically similar, but their testing, certification, and intended service differ significantly.
Specification Comparison
| Feature | API 5L | ASTM A106 |
|---|---|---|
| Scope | Line pipe for pipeline transportation | Seamless pipe for high-temperature service |
| Governing body | American Petroleum Institute | ASTM International |
| Pipe types | Seamless and welded (ERW, SAW, LSAW) | Seamless only |
| Common grades | Gr. B (PSL1/PSL2), X42, X52, X60, X65, X70 | Gr. A, Gr. B, Gr. C |
| Yield strength (Gr. B) | Min. 241 MPa (35 ksi) | Min. 241 MPa (35 ksi) |
| Tensile strength (Gr. B) | Min. 414 MPa (60 ksi) | Min. 414 MPa (60 ksi) |
| Max. temperature | Ambient/moderate | Up to 400°C (750°F) |
| Design code | ASME B31.4, B31.8 (pipelines) | ASME B31.1, B31.3 (process piping) |
| PSL levels | PSL1 (standard), PSL2 (enhanced testing) | Single quality level |
| Hydrostatic test | Mandatory per API 5L | Mandatory per ASTM A106 |
| Impact testing | Required for PSL2 only | Not required (unless supplementary) |
Grade Equivalence
API 5L Gr. B and ASTM A106 Gr. B share identical minimum yield (35 ksi) and tensile (60 ksi) strength values. The chemical composition limits are also nearly identical for carbon steel grades. However, the two specifications are not interchangeable without engineering review because testing and quality requirements differ.
| Property | API 5L Gr. B (PSL2) | ASTM A106 Gr. B |
|---|---|---|
| Carbon (max.) | 0.24% | 0.30% |
| Manganese (max.) | 1.20% | 0.29-1.06% |
| Sulfur (max.) | 0.015% | 0.035% |
| Phosphorus (max.) | 0.025% | 0.035% |
| Carbon equivalent (max.) | 0.25 (CE IIW) | Not specified |
API 5L PSL2 enforces tighter chemistry, mandatory impact testing, and maximum yield/tensile limits, making it more restrictive than ASTM A106.
When to Use Each Specification
Use API 5L for:
- Cross-country and in-plant pipeline systems
- Projects governed by ASME B31.4 (liquid pipelines) or B31.8 (gas pipelines)
- Sour service applications requiring NACE MR0175 compliance (PSL2 with Annex H)
- Higher-strength grades (X42 through X80) not available under ASTM A106
Use ASTM A106 for:
- Process piping within refineries and chemical plants
- High-temperature service up to 400°C per ASME B31.3
- Boiler and pressure vessel piping per ASME B31.1
- Applications requiring only seamless pipe construction
Key Selection Criteria
The decision between API 5L and ASTM A106 should follow the applicable design code. If your project piping class calls for ASME B31.4 or B31.8, specify API 5L. If ASME B31.3 or B31.1 governs, specify ASTM A106. For pipe types and manufacturing methods, note that ASTM A106 is limited to seamless pipe, while API 5L includes both seamless and welded options.
Leave a Comment
Have a question or feedback? Send us a message.