On this page 11 sections
What is API 5L Grade B?
Quick answer
- Standard
- API 5L / ISO 3183
- ISO 3183
- L245
- Minimum yield
- 245 MPa
- Product form
- Pipes
- Typical uses
- Oil and gas transmission pipelines; Gathering and flow lines
API 5L specifies seamless and welded (ERW/HFW, LSAW, SAWH) steel pipe for pipeline transportation systems. Grade B is the entry-level line-pipe grade, with a minimum yield of 245 MPa (35.5 ksi), and its ISO 3183 designation L245 gives the yield in MPa. Grade B pipe has a minimum tensile strength of 415 MPa.
Product Specification Level matters as much as grade. PSL 2 adds maximum yield and tensile limits, mandatory Charpy impact testing, tighter chemistry and carbon-equivalent limits, and full traceability. The delivery condition is shown by a suffix (for example N normalised, Q quenched and tempered, M thermomechanical), and Annexes cover sour service (H) and offshore service.
Key characteristics
- Minimum yield 245 MPa (L245)
- PSL 1 or PSL 2
- Seamless, ERW/HFW, LSAW or SAWH
- Sour (Annex H) and offshore (Annex J) options
What does the API 5L Grade B specification cover?
What are the mechanical properties of API 5L Grade B?
| Property | Value |
|---|---|
| Tensile strength | 415 MPa (60 ksi) |
| Yield strength (0.2% offset) | 245 MPa (35.5 ksi) |
| Elongation | Per formula in API 5L |
How much pressure can API 5L Grade B pipe take?
Barlow's formula (P = 2·S·t / D) gives a quick indication of pressure capacity. With the API 5L Grade B minimum yield of 245 MPa, the table shows the theoretical pressure at 100% of yield, and at a 0.72 design factor (the ASME B31.8 Class 1 factor) for Sch 40 and Sch 80.
| NPS | OD (mm) | Sch 40: WT → bar | Sch 80: WT → bar |
|---|---|---|---|
| NPS 2" | 60.33 | 3.91 → 318 / 229 | 5.54 → 450 / 324 |
| NPS 4" | 114.30 | 6.02 → 258 / 186 | 8.56 → 367 / 264 |
| NPS 6" | 168.28 | 7.11 → 207 / 149 | 10.97 → 319 / 230 |
| NPS 8" | 219.08 | 8.18 → 183 / 132 | 12.70 → 284 / 205 |
| NPS 10" | 273.05 | 9.27 → 166 / 120 | 15.09 → 271 / 195 |
| NPS 12" | 323.85 | 10.31 → 156 / 112 | 17.48 → 264 / 190 |
Sizes and weight chart
Outside diameters and walls follow ASME B36.10M for common sizes. Weights are calculated for API 5L Grade B at 7.85 g/cm³, and actual weights vary within manufacturing tolerances.
| NPS | OD (mm) | Sch 40 | Sch 80 | Sch 160 | XXS |
|---|---|---|---|---|---|
| NPS ½" | 21.34 | 2.77 / 1.27 | 3.73 / 1.62 | 4.78 / 1.95 | 7.47 / 2.56 |
| NPS ¾" | 26.67 | 2.87 / 1.68 | 3.91 / 2.19 | 5.56 / 2.89 | 7.82 / 3.64 |
| NPS 1" | 33.40 | 3.38 / 2.50 | 4.55 / 3.24 | 6.35 / 4.24 | 9.09 / 5.45 |
| NPS 1¼" | 42.16 | 3.56 / 3.39 | 4.85 / 4.46 | 6.35 / 5.61 | 9.70 / 7.76 |
| NPS 1½" | 48.26 | 3.68 / 4.05 | 5.08 / 5.41 | 7.14 / 7.24 | 10.15 / 9.54 |
| NPS 2" | 60.33 | 3.91 / 5.44 | 5.54 / 7.49 | 8.74 / 11.12 | 11.07 / 13.45 |
| NPS 2½" | 73.03 | 5.16 / 8.64 | 7.01 / 11.41 | 9.53 / 14.92 | 14.02 / 20.40 |
| NPS 3" | 88.90 | 5.49 / 11.29 | 7.62 / 15.27 | 11.13 / 21.35 | 15.24 / 27.68 |
| NPS 4" | 114.30 | 6.02 / 16.08 | 8.56 / 22.32 | 13.49 / 33.54 | 17.12 / 41.03 |
| NPS 6" | 168.28 | 7.11 / 28.26 | 10.97 / 42.56 | 18.26 / 67.56 | 21.95 / 79.21 |
| NPS 8" | 219.08 | 8.18 / 42.55 | 12.70 / 64.64 | 23.01 / 111.26 | 22.23 / 107.92 |
| NPS 10" | 273.05 | 9.27 / 60.30 | 15.09 / 96.00 | 28.58 / 172.31 | 25.40 / 155.13 |
| NPS 12" | 323.85 | 10.31 / 79.72 | 17.48 / 132.07 | 33.32 / 238.73 | 25.40 / 186.95 |
Quick weight calculator (density 7.85 g/cm³)
Testing and documentation
- Specification
- API 5L / ISO 3183
- Size range
- NPS ⅛" to 48" and larger (DN 6 – DN 1200+), schedules 5S to XXS, single random, double random and cut lengths
- Finish
- Annealed & pickled, bright annealed, mill finish, black, varnished, galvanised or 3LPE / FBE coated (by material)
- Ends
- Plain end (PE), bevelled end (BE, ASME B16.25), threaded (NPT / BSP), grooved
Testing & documents
- Chemical and mechanical (tension, flattening, flare/bend) tests
- Hydrostatic test or non-destructive electric test (UT/ET) on each length
- Dimensional and visual inspection
- Intergranular corrosion (stainless), impact (low-temperature), hardness (sour service) when specified
- PMI and third-party inspection on request
- EN 10204 3.1 certificate; 3.2 with third-party inspection
Where is API 5L Grade B used?
- Oil and gas transmission pipelines
- Gathering and flow lines
- Water and slurry pipelines
- Refinery and terminal interconnecting lines
- Piling and structural uses (non-pressure)
Industries
What to include in your enquiry
- Specification and grade: API 5L Grade B
- NPS × schedule (or OD × WT), seamless/welded, length, ends; PSL 1 / PSL 2 and delivery condition
- Quantity and destination
- Tests and certificates (3.1 / 3.2)
Explore more
Carbon Steel pipes
Guides
Comparisons & articles
Frequently asked questions
What is API 5L Grade B equivalent to?
Its ISO 3183 designation is L245. It's often dual-certified with ASTM A106 Grade B and A53 Grade B, but each specification has its own requirements.
What is the difference between PSL 1 and PSL 2?
PSL 2 adds mandatory impact testing, maximum strength limits, tighter chemistry and carbon-equivalent limits, and stricter inspection and traceability requirements.
What is API 5L Grade B used for?
Oil and gas transmission pipelines, Gathering and flow lines, Water and slurry pipelines, Refinery and terminal interconnecting lines.
What is the minimum yield strength of API 5L Grade B?
245 MPa (245 MPa (35.5 ksi)), with a minimum tensile strength of 415 MPa (60 ksi).
How do I calculate the weight of API 5L Grade B pipe?
kg/m = π × (OD − WT) × WT × 7.85 / 1000 for carbon steel, with dimensions in mm. See the weight chart on this page.
Which documents are supplied with API 5L Grade B?
EN 10204 3.1 mill test certificate as standard, with 3.2 and third-party inspection on request.