Two lengths of API 5L X65 can sit side by side on a pipe rack and still be very different products. One might be seamless, quenched and tempered, and certified X65QS for sour gas. The other might be welded from thermomechanically rolled plate as X65M, ideal for a sweet export line and never intended for H2S. The suffix tells you which. This hub explains how API 5L line pipe is actually specified, covering grade, PSL, delivery condition, manufacturing route and the annexes most GCC pipeline specifications call up. There is a page for each grade from Grade B to X70, all within the API line pipe and OCTG range.

API 5L Pipe Grades: Grade B to X70

API 5L Grade B Line Pipe

The entry grade, with a minimum yield of 245 MPa. It is the natural fit for water injection, firewater, utility and low-pressure gathering lines where strength is not the limiting factor and simple field welding matters more. See API 5L Grade B line pipe.

API 5L X42 Line Pipe

A small step up to 290 MPa minimum yield. X42 turns up on gathering and distribution systems and on smaller-bore lines where a designer wants a margin over Grade B without moving into higher-strength welding procedures. See API 5L X42 pipe.

API 5L X52 Line Pipe

With 360 MPa minimum yield, X52 is the grade many field flowline and gathering specifications default to. It balances strength, weldability and availability, and it is widely produced in PSL2 sour service condition. See API 5L X52 line pipe.

API 5L X60 Line Pipe

At 415 MPa minimum yield, X60 lets a transmission line run a noticeably thinner wall than X52 at the same pressure. It is often chosen where pipe weight and welding time start to dominate project cost. See API 5L X60 pipe.

API 5L X65 PSL2 Line Pipe

X65 raises minimum yield to 450 MPa and is a regular choice for high-pressure onshore and offshore transmission. In PSL2 it is supplied only as quenched and tempered (Q) or thermomechanically rolled (M), and it is available to Annex H for sour service and Annex J for offshore. See API 5L X65 PSL2 line pipe.

API 5L X70 Line Pipe

The highest grade covered here, with 485 MPa minimum yield, used on large-diameter, high-pressure trunk lines where the wall saving over X65 pays for tighter welding control. See API 5L X70 pipe.

API 5L Sour Service Line Pipe

Not a separate grade but PSL2 pipe ordered to Annex H, with extra chemistry limits, hardness control and HIC testing. This page pulls together what a sour line pipe order needs, grade by grade. See API 5L sour service line pipe to NACE MR0175.

How to Read an API 5L Grade Designation

A full PSL2 designation carries more than the grade. The letters that follow tell you how the steel was processed and which annex the pipe was made to, and they are worth checking on every mill certificate.

Suffix	Meaning	Example
R	As-rolled	X42R
N	Normalised, normalising rolled or normalising formed	X52N
Q	Quenched and tempered	X65Q
M	Thermomechanically rolled or formed	X70M
S (added after the condition letter)	Sour service, made to Annex H	X65QS
O (added after the condition letter)	Offshore service, made to Annex J	X65QO

ISO 3183 uses the same system with metric names, so X65QS is L450QS. Not every condition is offered for every grade. X65 and X70 in PSL2, for example, are available only in Q or M condition.

Choosing API 5L Line Pipe by Service Condition

Service condition	Typical grade and level	What to specify
Water injection, firewater, utility	Grade B or X42, PSL1 or PSL2	Internal lining or coating if the water is aggressive
Sweet oil and gas gathering and flowlines	X42 to X52, PSL2	Charpy test temperature to suit minimum design temperature
Sour gas or sour crude (H2S present)	X52 to X65, PSL2 Annex H (for example X52NS, X65QS)	HIC and SSC testing, hardness survey, operator sour specification
High-pressure onshore transmission	X60 to X70, PSL2	Weldability (carbon equivalent), DWTT on larger welded sizes
Offshore and subsea lines	X52 to X65, PSL2 Annex J (for example X65QO)	Tighter dimensional tolerances, extra NDT
Sour offshore lines	PSL2 made to both Annex H and Annex J	Combined requirements of both annexes

Grade	Min. yield (MPa)	Min. tensile (MPa)	PSL2 max. yield (MPa)	PSL2 max. tensile (MPa)
Grade B (L245)	245	415	450	760
X42 (L290)	290	415	495	760
X52 (L360)	360	460	530	760
X60 (L415)	415	520	565	760
X65 (L450)	450	535	600	760
X70 (L485)	485	570	635	760

Worked example: how grade changes wall thickness

The basic hoop stress relationship used in pipeline codes is t = P × D / (2 × S × F), where P is design pressure, D is outside diameter, S is specified minimum yield strength and F is the design factor.

Take an NPS 12 line (323.9 mm OD) at 10 MPa (100 bar) with a design factor of 0.72:

Grade	SMYS (MPa)	Pressure-design wall (mm)
X52	360	6.25
X65	450	5.00
X70	485	4.64

Moving from X52 to X65 cuts the pressure-design wall by about 20%, and pipe weight drops by a similar amount. This is an illustration only. The real wall comes from the governing code (ASME B31.4, B31.8 or the operator's design standard), the location class and design factor, corrosion allowance, mill tolerance and minimum wall for handling. It does show why long, high-pressure lines move up the grade table.

API 5L Manufacturing Routes: Seamless, HFW, LSAW and Spiral

Route	How it is made	Where it is usually chosen	PSL2 notes
Seamless pipe (SMLS)	Pierced and rolled from a solid billet	Smaller diameters, heavy walls, sour and high-pressure service	No weld seam to inspect or qualify
HFW (high-frequency electric welded)	Formed from coil and welded without filler metal	Small to medium diameters, gathering and distribution	PSL2 requires high-frequency welding; low-frequency ERW is not permitted
LSAW (longitudinal submerged arc welded)	Formed from plate with a single straight seam	Large diameters and heavy walls, high-pressure transmission and offshore	Common route for large-diameter sour and Annex J pipe
SAWH (helical or spiral submerged arc welded)	Formed from coil with a helical seam	Large diameters at moderate pressure, water transmission	Accepted in PSL2; less common for sour or offshore service

For a fuller comparison of welded and seamless pipe beyond line pipe, see the seamless vs welded pipe guide.

API 5L Line Pipe Sizes, Ends and Lengths

API 5L specifies wall thickness in millimetres, and many common walls match the STD and XS values of ASME B36.10M.

NPS	DN	OD (mm)	OD (in)	STD wall (mm)	XS wall (mm)
2	50	60.3	2.375	3.91	5.54
4	100	114.3	4.500	6.02	8.56
6	150	168.3	6.625	7.11	10.97
8	200	219.1	8.625	8.18	12.70
12	300	323.9	12.750	9.53	12.70
16	400	406.4	16.000	9.53	12.70
20	500	508.0	20.000	9.53	12.70
24	600	610.0	24.000	9.53	12.70
30	750	762.0	30.000	9.53	12.70
36	900	914.0	36.000	9.53	12.70
42	1050	1067.0	42.000	9.53	12.70
48	1200	1219.0	48.000	9.53	12.70

Ends. Line pipe is normally supplied plain-end and bevelled for field welding, with a 30° bevel (tolerance +5°, 0°) and a 1.6 mm root face (±0.8 mm). Other weld preparations can be ordered to suit the contractor's welding procedure.

Tolerances. OD, wall, out-of-roundness and straightness tolerances follow API 5L and vary with diameter and manufacturing route. Annex J tightens several of them for offshore pipe.

Lengths. API 5L orders pipe in approximate length categories, most often around 6 m or 12 m, with minimum and minimum-average lengths set by the standard. A full 12 m length will not fit inside a 40 ft container, so 11.8 m cut lengths are the usual choice for containerised shipments into Sohar, Duqm, Salalah, Jebel Ali or Dammam. Longer lengths ship on flat racks or as break bulk.

Sizes are supplied to specification. Send your OD, wall and length.

API 5L Chemistry, Mechanical Testing and PSL2 Controls

Full chemistry for each grade sits on its grade page. At hub level, these are the controls that separate a PSL2 order from a PSL1 order:

Property	PSL1	PSL2
Carbon, manganese, phosphorus, sulphur	Maximum limits	Tighter maximums
Carbon equivalent	Not limited	Limited: CEIIW 0.43 max or CEPcm 0.25 max for most grades up to X70, depending on carbon content
Microalloying (Nb, V, Ti)	Limited in total	Limited in total, with the sum controlled per grade
Yield and tensile	Minimum only	Minimum and maximum
Yield-to-tensile ratio	Not limited	0.93 max for most grades
Charpy impact test	Not mandatory	Mandatory, at 0 °C unless a lower temperature is ordered
DWTT (drop-weight tear test)	Not required	Required on larger-diameter welded pipe in gas service
Hydrostatic test	Every length	Every length
Weld seam NDT	Required	More extensive, full length
Sour hardness (Annex H)	Not available	250 HV10 max in body, weld and heat-affected zone

The API 5L PSL1 vs PSL2 guide goes through each requirement with examples.

Line Pipe Standards: API 5L, ISO 3183 and Operator Specifications

Standard	Relationship to API 5L
ISO 3183 / EN ISO 3183	Technically aligned with API 5L, using L-grade names (L360 = X52)
EN 10208-2	Older European line pipe standard, superseded by EN ISO 3183
GB/T 9711	Chinese national line pipe standard based on ISO 3183

Operators in the region issue their own line pipe specifications that sit on top of API 5L. Typical additions include lower carbon equivalent, lower sulphur, higher Charpy energy at a lower test temperature, HIC testing even outside Annex H, tighter tolerances and witnessed inspection. Send your operator or project specification with the enquiry and the offer will be prepared against it.

Sour and Offshore Line Pipe: Annex H and Annex J

Annex H (sour service) applies to PSL2 pipe for H2S environments under NACE MR0175 / ISO 15156-2. It adds tighter chemistry, especially sulphur, a 250 HV10 hardness limit, HIC testing to NACE TM0284 and SSC testing to NACE TM0177 where specified. It is the specification behind almost every sour flowline order in Oman and Saudi Arabia. Grade-by-grade detail is on the sour service line pipe page, and the NACE MR0175 sour service guide explains the standard itself.

Annex J (offshore service) applies to PSL2 pipe for offshore and subsea lines. It tightens dimensional tolerances and adds testing and inspection suited to offshore installation. Pipe can be ordered to both annexes when an offshore line also carries sour fluid.

State your sour service and testing requirements (HIC, SSC, hardness survey) in the RFQ. They are confirmed at quotation.

API 5L Line Pipe Price: What Moves the Quote

Line pipe prices follow steel markets and mill loading, so they are quoted per enquiry. The biggest drivers:

Grade, PSL and delivery condition. PSL2 costs more than PSL1, Q and M conditions more than R or N, and Annex H or J more again.
Manufacturing route. Seamless, HFW, LSAW and spiral pipe price differently at the same size.
Size and wall. Heavy walls and large diameters can limit which mills can quote.
Quantity. Mill minimums apply, particularly for LSAW and Annex H orders.
Stock or mill order.
Testing. HIC, SSC, DWTT and extra Charpy temperatures.
Coating. External or internal coating, if required.
Certification and inspection. EN 10204 3.1 or 3.2, and third-party witness points.
Incoterm and destination port.

Quotations are available in USD, OMR, AED, SAR, QAR, KWD and BHD, on EXW, FOB, CFR or CIF terms.

What to send for an API 5L quotation

Grade and delivery condition, PSL, any annex (H or J), manufacturing route (seamless or welded), OD, wall, length, quantity, end finish, Charpy test temperature, testing requirements, coating, certification level, inspection requirement, destination port and required date.

Line Pipe Certification, Marking and Inspection

API 5L line pipe is supplied with EN 10204 3.1 mill test certificates as standard, and EN 10204 3.2 certificates on request. Inspection by the buyer's nominated third-party agency can be arranged; state your requirement in the RFQ. Each length carries the mill's marking, including grade with its full suffix, PSL, size, heat number, and, where the mill holds the licence, the API monogram. Checking that the stencil matches the certificate, suffix included, is the quickest way to catch an X65M delivered against an X65QS order. The MTC and EN 10204 certification guide explains 3.1 and 3.2 in detail.

Packing, Shipping and Yard Storage in the Gulf

Lead time is confirmed at quotation.

Bevel protectors on both ends so the weld preparation arrives clean and undamaged
Varnish or temporary external coating on bare pipe where specified
Wooden or rubber spacers between coated lengths to protect the coating in transit
Strapped bundles for smaller diameters, and individual lifting for large-diameter pipe
UV-stable end protectors for yard storage

Bare line pipe left on coastal laydown yards picks up surface rust quickly from humidity and airborne salt, and blowing sand damages unprotected bevels. Store pipe on sleepers or berms off the ground, keep end protectors on until stringing, and shade coated pipe or specify a UV-resistant coating if it will wait months before installation.

Matching Fittings and Flanges for API 5L Pipelines

Fittings and flanges should match the line pipe's strength so the pipeline has no weak point:

High yield pipeline fittings and flanges hub
MSS SP-75 WPHY high yield fittings for elbows, tees and reducers
ASTM A694 F52 flanges, F60 flanges, F65 flanges and F70 flanges
Large diameter flanges to ASME B16.47 for trunk line sizes
Anchor flanges and RTJ ring type joint flanges for pipeline and high-pressure connections

For downhole tubulars, see the API 5CT casing and tubing hub.

Where API 5L Line Pipe Is Used

Oil and gas: flowlines, gathering systems, trunk and export pipelines
Upstream oil and gas and sour service: Annex H sour flowlines and gathering lines
LNG and gas processing: feed gas and sales gas pipelines
Marine and offshore: Annex J offshore and subsea lines

Useful references: pipe schedule, NPS and wall thickness guide, pipe weight chart and pipe pressure rating chart.

API 5L Line Pipe FAQ

What do the letters after an API 5L grade mean, such as X65QS?

The first letter after the grade is the delivery condition: R for as-rolled, N for normalised, Q for quenched and tempered, M for thermomechanically rolled. A following S means the pipe is made to Annex H for sour service, and O means Annex J for offshore service. X65QS is quenched and tempered X65 made for sour service.

Can PSL2 line pipe be ERW?

Yes, but only high-frequency welded (HFW) pipe. Low-frequency ERW is not permitted for PSL2. LSAW and spiral SAW pipe are also accepted in PSL2.

Should I choose X52 or X65 for a new pipeline?

X65 allows a wall roughly 20% thinner than X52 at the same pressure and diameter, which reduces steel weight and welding time on long lines. X52 is easier to weld, widely available in sour condition and often preferred for flowlines and smaller diameters. The governing design code and operator specification make the final call.

What is Annex J in API 5L?

Annex J covers PSL2 pipe for offshore service. It tightens dimensional tolerances and adds testing and inspection for offshore installation. Pipe can be ordered to Annex H and Annex J together for sour offshore lines.

What length of line pipe fits in a shipping container?

A 40 ft container takes lengths up to about 11.8 m, so 11.8 m cut lengths are the usual choice for containerised shipping. Full 12 m random lengths ship on flat racks or as break bulk.

What should I include in an API 5L enquiry?

Include the grade with delivery condition, PSL, any annex, seamless or welded, OD, wall, length, quantity, end finish, Charpy test temperature, testing, coating, certification, inspection, destination port and required date.

Request a Quote for API 5L Line Pipe

Send the grade with its full suffix, PSL, size, quantity and destination port, and attach the line list or operator specification if you have one. Every enquiry is checked against API 5L before the offer goes out, so a missing annex or an unclear delivery condition is raised at the start rather than at inspection.

Request a Quotation

API 5L Line Pipe: Grades, PSL, Delivery Conditions and Annexes