API 5L Grade B Pipe: PSL1 and PSL2 Specifications

API 5L Grade B is the entry-level transmission grade in API Specification 5L and the most widely traded carbon steel line pipe grade worldwide. On gathering systems, injection lines, and medium-pressure distribution networks across Africa, the Middle East, and South America, Grade B (L245) pipe delivers adequate strength for the majority of applications at the lowest material cost in the API 5L grade ladder. Selecting between PSL1 and PSL2 — and specifying the correct delivery condition — determines whether a Grade B order performs in service or becomes a liability.

ZC Steel Pipe supplies API 5L Grade B line pipe as both seamless and ERW in NPS 2" to NPS 24" (60 mm to 610 mm OD), PSL1 and PSL2, for projects across Africa, the Middle East, South America, and Southeast Asia. EN 10204 3.1 MTCs are standard on all orders; 3.2 is available on request.

What Is API 5L Grade B?

API Specification 5L, 46th Edition (effective November 2018) defines Grade B — designated L245 in the metric SI system — as the minimum-strength grade in the API 5L line pipe family. The SI designation encodes the minimum yield: 245 MPa.

Grade B is the baseline of the API 5L grade ladder:

Grade B is manufactured as both seamless and ERW. For gathering and distribution lines below approximately 7 MPa (1,015 psi) operating pressure, Grade B PSL1 is the standard specification. For sour service, sub-zero environments, or long-distance transmission, PSL2 with an appropriate delivery condition is required.

Mechanical Properties

All values from API Specification 5L, 46th Edition.

PSL1 — L245 / Grade B

PSL2 — L245 / Grade B

For the complete API 5L grade ladder with PSL1 and PSL2 tensile and Charpy properties, see the API 5L specification tables →

To calculate design wall thickness for Grade B at your MAOP, use the Pipeline Design Calculator →

Chemical Composition

All values from API Specification 5L, 46th Edition.

PSL1 — L245 / Grade B

PSL1 imposes no silicon limit, no carbon equivalent requirement, and no restriction on maximum yield strength. These gaps are what make PSL1 unsuitable for sour service and low-temperature service without supplementary specifications.

PSL2 — L245 / Grade B by Delivery Condition

The BQ condition achieves the lowest carbon content (≤ 0.18%) through quench-and-temper processing. BM (thermomechanically controlled) is the most widely produced ERW Grade B PSL2 condition and offers weld-friendly carbon equivalent alongside the microalloying elements that support Charpy performance.

Standard Sizes (ASME B36.10M-2018)

Grade B line pipe is available across all standard ASME B36.10M sizes. The table below shows common NPS with Standard (STD) and Extra Strong (XS) schedules. All dimensions from ASME B36.10M-2018.

For NPS 14 and above, the Standard (STD) wall is constant at 9.52 mm (0.375 in) per ASME B36.10M-2018, regardless of pipe size. ZC Steel Pipe supplies Grade B in NPS 2" to NPS 24" as both seamless and ERW.

Delivery Conditions for PSL2

The delivery condition suffix designates the heat treatment route and is appended to the grade name (BN, BQ, BM, or BR). Each condition produces a distinct microstructure and chemistry profile:

For sour service Annex H applications, the BM or BQ delivery condition is preferred because both achieve the carbon equivalent (CE_IIW ≤ 0.43) needed to maintain NACE MR0175 / ISO 15156 hardness compliance after field girth welding.

Grade B vs X42 vs X52 — When to Upgrade

Note that at PSL1, X42 has the same minimum tensile as Grade B — only the yield differs. Moving from Grade B to X42 allows thinner walls at the same operating pressure without a tensile step-up. Upgrading to X52 delivers a combined yield and tensile increase, enabling meaningful wall reduction on long-distance lines. For high-pressure mainline service above 10 MPa (1,450 psi), X65 or X70 is the standard in modern projects.

For a detailed PSL1 versus PSL2 decision framework, see API 5L PSL1 vs PSL2 Line Pipe Selection Guide →

Purchase Order Guidance

Minimum Required PO Line Items

• Standard: API Specification 5L, 46th Edition
• PSL level: PSL1 or PSL2 — always specify explicitly
• Grade: Grade B or L245
• Delivery condition (PSL2 only): BN, BQ, or BM
• Pipe form: seamless or ERW
• Size: OD × wall thickness × length (DRL or fixed)
• End finish: plain end (PE) or bevelled end (BE, 30° ± 5°)
• Supplementary requirements if applicable: Annex H (sour service), Charpy temperature and energy, third-party inspection, EN 10204 3.1 MTC

The PSL1 Trap

The single most common procurement error with Grade B: specifying "API 5L Grade B" without a PSL level. Without a declared PSL, API 5L defaults to PSL1 — and PSL1 Grade B has no Charpy requirement, no maximum hardness cap, and no carbon equivalent limit. In sour service, this pipe can pass hydrostatic test and carry a clean MTC yet fail NACE MR0175 hardness limits and initiate hydrogen-induced cracking under H2S partial pressure. In cold climates, an uncertified PSL1 seam can fail Charpy requirements. Always specify PSL2 for sour service, low-temperature service below 0 °C (32 °F), and any application where the girth weld HAZ hardness or seam toughness must be certified.

What to Verify on the MTC

• PSL level declared in the grade designation on the MTC header
• Delivery condition suffix (BN, BQ, BM) matches the PO
• Carbon equivalent values — CE_IIW and CE_Pcm — within PSL2 limits
• Charpy impact test results: temperature, specimen size, average and minimum absorbed energy
• Hydrostatic test pressure and calculation basis
• Seam UT inspection confirmation for ERW PSL2 pipe
• Ca treatment and sulphur content for Annex H sour service orders

For the full EN 10204 MTC review procedure, see Pipe Mill Test Certificate Guide →