API 5L Pipe Specification

API 5L specification (API Spec 5L, Line Pipe) is the buying and manufacturing rulebook for steel line pipe used in pipeline transportation systems. The current edition is the 47th edition (published June 2026; Monogram Program effective date 1 July 2027 per API advisory). This page is the specification hub: PSL1 vs PSL2, grade map, tolerances and RFQ language. Detailed chemistry and strength for individual grades live on the grade pages — we deep-link them and do not try to rank as those grade primaries.

Mejor Steel is an export trading company in Anyang, China — not an API monogram pipe mill. We place orders with partner mills that manufacture to Spec 5L, name the producing mill on the quotation, and forward the mill’s inspection documents with the shipment. See How we supply, EN 10204 3.1 vs 3.2, MTC guide.

Edition note (2026-11-07): API announced the 47th edition of Spec 5L on 2 June 2026. Many POs still reference the 46th edition (2018) until project documents flip. State the edition on every RFQ. Figures on grade pages follow the soft-metric values we verified for those grades; confirm against the edition named on your PO.

API 5L at a glance (47th edition)

What changed in the 47th edition (vs the 46th)

Most supplier pages still describe the 46th edition (2018). The 47th edition lists more than 15 changed topic areas. The ones that change what a buyer writes on a purchase order:

Which edition does my order use? The one written on the purchase order. Publication of a new edition does not change an existing contract. For new orders we quote to the 47th edition unless your project specification names the 46th.

Pipe grades and delivery conditions

An API 5L grade name has two forms: L + minimum yield in MPa (ISO style, e.g. L360) or X + minimum yield in ksi (US style, e.g. X52). For PSL 2 the suffix letter is part of the grade:

PSL 1 grades: L175/A25, L175P/A25P, L210/A, L245/B, L290/X42, L320/X46, L360/X52, L390/X56, L415/X60, L450/X65, L485/X70.

PSL 2 grades: BR, X42R; BN–X60N; BQ–X100Q; BM–X120M (see Table 1 of the 47th edition for the exact list per delivery condition).

Reading a grade designation

Both naming systems describe the same steel. Write one on the purchase order, either X65Q or L450Q, and the mill will usually stencil both.

Which pipe types are allowed for each grade (Table 2)

Helical-seam pipe (SAWH/SSAW) starts at D ≥ 114.3 mm; double-seam pipe only at D ≥ 914 mm; threaded ends only up to 508 mm and only PSL 1.

How each PSL 2 delivery condition is made (Table 3)

Practical reading: most LSAW and SSAW X60–X80 is “M” (TMCP plate or coil); heavy-wall seamless X65–X70 is “Q”; small-bore ERW for gathering lines is often “N” or “M” with weld-seam heat treatment.

PSL 1 vs PSL 2 — the differences that cost money

Rule of thumb: if your design code, client or route includes sour gas, offshore, low temperature or high-pressure gas transmission, you need PSL 2. Most gas transmission projects and EPC tenders specify PSL 2 as standard. For a deeper comparison see API 5L PSL1 vs PSL2.

How to choose PSL, grade and pipe type (decision guide)

Rules of thumb that save rework:

• Grade substitution needs approval. Clause 9.1 says pipe made as X60 or higher cannot be shipped against an order for X52 or lower without the purchaser’s approval. PSL 2 also caps maximum yield, so an X65 heat cannot be certified as X52 PSL 2 unless its yield falls inside the X52 range of 360–530 MPa.
• Dual-grade stencils are common in stock. Grade B/X42 or X52/X60 dual-marked pipe is valid only when the heat meets the chemistry and tensile limits of both grades.
• Delivery-condition letter matters for welding. N (normalized) and Q (quenched and tempered) suit seamless and thick wall. M (thermomechanical rolled) gives the lowest carbon and CE for field welding, and is a welded-pipe route.
• Wall thickness drives cost more than grade. Moving from X52 to X65 at the same pressure cuts the wall by about 20 %, so tonnage, freight and welding time all fall. See the worked example below.
• Test temperature belongs on the PO. The PSL 2 CVN default is 0 °C. Arctic or deep-buried lines often specify −20 °C to −46 °C, and the mill must know this before it melts the steel.

Seamless vs ERW/HFW vs LSAW vs SSAW for API 5L

PSL 1 (Table 4), % max

PSL 1 grades A25 (C 0.21, Mn 0.60), A25P (C 0.21, Mn 0.60, P 0.045–0.080) and A (C 0.22, Mn 0.90) are the same for seamless and welded pipe. Cu, Ni, Cr ≤ 0.50 %, Mo ≤ 0.15 %; for Grade B, Nb + V ≤ 0.06 % unless agreed; no deliberate boron (residual ≤ 0.001 %). For each 0.01 % carbon below the maximum, Mn may rise 0.05 % (to 1.65 % for B–X52, 1.75 % above X52 and below X70, 2.00 % for X70). Nb + V + Ti ≤ 0.15 %.

PSL 2 (Table 5), all standard grades, % max

Footnote limits that buyers check on the MTC (Table 5, 47th edition):

CEIIW applies when C > 0.12 %, CEPcm when C ≤ 0.12 % (product analysis). CEIIW = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15; CEPcm = C + Si/30 + Mn/20 + Cu/20 + Ni/60 + Cr/20 + Mo/15 + V/10 + 5B. Thicker walls (t > 25 mm) and sour pipe (Annex H) have their own agreed or tighter limits — we put them on the quotation.

Tensile properties

PSL 1 (Table 6), minimum

PSL 2 (Table 7), min–max

Minimum elongation is not a fixed number: it is calculated from the test-piece area and the grade’s tensile strength (Af = C·A⁰·²/U⁰·⁹), so it varies with wall thickness and specimen type. Read it on the MTC against the formula, not against a table copied from another site.

PSL 2 Charpy (Table 8), pipe body, full-size, minimum average, J

Standard test temperature is 0 °C (32 °F); lower temperatures are agreed on the order. Pipelines that need ductile fracture arrest (gas, CO₂) use Annex G values instead.

Dimensions and tolerances

API 5L allows any outside diameter and wall thickness inside Table 9; standard size combinations come from ASME B36.10M and ISO 4200. Use our and weight calculator for OD, wall and kg/m.

Diameter (Table 10, pipe body)

Pipe ends (100 mm at each end) have tighter limits, e.g. ±0.005D max ±1.6 mm for welded pipe 168.3–610 mm.

Wall thickness (Table 11)

Random lengths, plain-end pipe (Table 12)

Threaded-and-coupled 12 m pipe has a higher minimum of 6.71 m. Container shipments usually call for 11.8 m maximum; state it on the order.

Length, straightness, mass

Out-of-roundness (Table 10)

Pipe-end diameter for D > 610–1422 mm: seamless ±2.0 mm, welded ±1.6 mm; for 60.3–168.3 mm: −0.4 to +1.6 mm.

Weld seam tolerances (9.13)

End finish (9.12)

PSL 2 pipe is plain end only. Plain ends with t > 3.2 mm are beveled 30° (+5°/−0°) with a 1.6 ± 0.8 mm root face unless another end prep is ordered (e.g. compound bevel for heavy wall, square cut for mechanical couplings). Threaded and coupled ends (Annex F couplings) are PSL 1 only.

Weight and hydrotest pressure for common sizes

API 5L mass per unit length: m = t (D − t) × 0.02466 kg/m (D, t in mm). Hydrotest pressure for plain-end pipe: P = 2 S t / D, where S is a percentage of the grade’s SMYS (Table 26): 60 % for D ≤ 141.3 mm, 75 % for 141.3–219.1 mm, 85 % for 219.1–< 508 mm, 90 % for D ≥ 508 mm (X42 and above). The standard does not require test pressure above 20.5 MPa for these grades, so 20.5 appears as the cap below.

Values are calculated with the 47th-edition equations for plain-end pipe at standard test pressure. Full size range: , , weight calculator.

Hydrotest rules (10.2.6)

Nondestructive inspection (Annex E; Annex K for sour/offshore)

NDT personnel are qualified to ISO 9712 or ASNT SNT-TC-1A; the 47th edition revised this certification clause.

Test frequency (Table 17 PSL 1, Table 18 PSL 2)

Inspection documents and MTC (10.1)

Every order ships with the producing mill’s EN 10204 3.1 or 3.2 certificate, passed on unaltered; where the order asks for 3.2, we arrange your nominated inspector (for example SGS, BV, TÜV, DNV or Lloyd’s) at the mill.

Coating and lining

API 5L covers bare pipe; temporary mill varnish is common unless the order says bare. Permanent coatings are bought to their own standards: 3LPE/3LPP to ISO 21809-1 or DIN 30670/30678, FBE to ISO 21809-2 or CSA Z245.20, concrete weight coating to ISO 21809-5, internal epoxy lining to API RP 5L2 (gas) or AWWA C210 (water). State cutback length and holiday test voltage on the order. See coated line pipe.

From design pressure to grade and wall (worked example)

Barlow: t = P D / (2 S F E T). For a gas line under ASME B31.8 Class 1 Division 2 (F = 0.72, E = 1.0, T = 1.0), 12.75 in (323.9 mm), MAOP 10 MPa:

Corrosion allowance, location class and code checks are added by the designer; higher grades cut tonnage but raise PSL 2 CE and toughness demands. Send the result to us as OD × WT × grade for a price.

Marking — how to read an API 5L stencil

Example from the 47th edition (USC units):

X API Spec 5L 20 0.500 X52M PSL 2 SAWL Y Z

Sour pipe adds S and the class: X52MSA. Offshore adds O. If the hydrotest pressure is above the standard value, “TESTED” and the pressure follow.

Sour service (Annex H) and offshore (Annex J) in numbers

Annex H chemistry, selected grades (Table H.1), % max

Also: Al ≤ 0.060 %, N ≤ 0.012 %, Cu ≤ 0.35 %, Ni ≤ 0.30 %, Cr ≤ 0.30 %, Mo ≤ 0.15 %, B ≤ 0.0005 %, Ca ≤ 0.006 % (Ca/S ≥ 1.5 for Ca-treated welded pipe). Seamless S may go to 0.010 %; seamless CEPcm may be 0.03 higher.

Annex H mechanical and HIC acceptance

Annex J offshore hardness

Annexes buyers actually need to name

API 5L PDF — where to get the standard

The legitimate source of the API 5L PDF is the API webstore (47th edition, 206 pages). Free “API 5L PDF” copies circulating online are usually old editions or unlicensed copies; they are not valid for contract or inspection use. This page gives the values buyers need for quoting; for the full text buy the standard. We send a one-page grade, PSL and tolerance summary with every quotation on request.

How to order API 5L line pipe (RFQ checklist)

Section 7.1 of the standard lists the mandatory order items; Section 7.2 lists more than 50 optional ones. A complete enquiry contains:

1. Quantity (tonnes or metres) and delivery schedule.
2. PSL 1 or PSL 2.
3. Pipe type: SMLS, HFW (ERW), SAWL (LSAW) or SAWH (SSAW).
4. Edition: API 5L 47th edition, or the edition your project specification names.
5. Grade including suffix (e.g. X65M, X52N) — “X65” alone is incomplete for PSL 2.
6. OD × wall (mm or in), e.g. 323.9 × 9.53 mm.
7. Length: random (12 m / 40 ft) or approximate, and whether jointers are allowed.
8. Annexes: H (with sour class A/L/F), J, G, N, B.
9. Charpy test temperature if below 0 °C.
10. End finish: standard bevel (see End finish above), a special bevel drawing, square cut, or threaded (PSL 1 only).
11. Coating system and its standard (see Coating and lining above).
12. Dual certification if needed (e.g. API 5L/ISO 3183, or API 5L Gr B/ASTM A106 B/A53 B for seamless).
13. Inspection: EN 10204 3.1 or 3.2, third party (SGS, BV, TÜV), witness points.
14. Destination port and Incoterm.

Missing items we see most: no grade suffix, no sour class, no edition, and Charpy temperature left blank.

Which Mejor Steel page fits your API 5L enquiry

Larger or special size combinations: drawings and mill data supplied on request — get a quote.

API 5L vs ISO 3183 vs ASTM A106

Common API 5L mistakes on purchase orders

1. Grade without suffix. “X52 PSL 2” can be delivered as N, Q or M — three different steels. Say which.
2. “Sour service” without a class. Under the 47th edition the class (A, L, F) decides the HIC test solution.
3. Old MTCs. A sour X65 certificate showing 720 MPa tensile does not meet the 47th-edition sour ceiling of 685 MPa.
4. Copying elongation from a website. Minimum elongation depends on test-piece size; check it with the formula.
5. Threads on PSL 2. Threaded ends are PSL 1 only.
6. SSAW below 114.3 mm or LW above X70. Not permitted by Table 2.
7. Leaving length open. Name the Table 12 designation and any container or site limit.

FAQ