API 5L PSL1 vs PSL2 - What Is the Difference?
PSL1 and PSL2 are the two Product Specification Levels defined by API 5L for steel line pipe. They are not grades. They are quality tiers layered on top of the grade system.
API 5L grades from Grade B through X70 can be manufactured to either PSL1 or PSL2. Grade A and A25 exist only under PSL1, while X80 is available only under PSL2. The two levels impose different requirements on chemistry, mechanical properties, testing, traceability, and annex availability.
PSL1 is the standard requirement set for general pipeline service. PSL2 is the enhanced requirement set used when a project needs tighter chemistry, mandatory impact testing, mandatory NDT, higher traceability, and access to Annex H sour service or Annex J offshore requirements. Use this page together with our API 5L line pipe overview when finalizing the RFQ.
Standard project quality level
Suitable for general utility service, water transmission, low-pressure gas distribution, and non-critical applications where impact testing and enhanced traceability are not mandated.
Enhanced project quality level
Used for transmission pipelines, H2S service, offshore lines, stricter field weldability, and project specs requiring CVN, NDT, controlled delivery condition, and full pipe traceability.
Quick answer
PSL1 focuses on minimum compliance. PSL2 controls chemistry, toughness, NDT scope, maximum strength, and documentation more tightly. Most major transmission and offshore projects default to PSL2.
Important note
There is no PSL3 in API 5L. The standard defines only PSL1 and PSL2.
Master Comparison Table
This table concentrates the commercial and technical differences buyers usually need during specification review.
| Requirement | PSL1 | PSL2 |
|---|---|---|
| Grade range | Grade A through X70 | Grade B through X80 |
| Size range | 0.405 in through 80 in OD | 2.375 in through 80 in OD |
| Chemical limits | Standard | Stricter, lower P and S, Si mandatory |
| Carbon equivalent | Not required | Mandatory |
| Yield and tensile limits | Minimum only | Minimum plus maximum |
| Yield-to-tensile ratio | No limit | <= 0.93 |
| CVN impact testing | Not required | Mandatory for most grades |
| NDT | Not required | Required for body and weld seam |
| ERW weld frequency | No minimum specified | >= 100 kHz |
| Traceability | Heat and test unit | Heat, test unit, individual pipe |
| Weld repair | Permitted by agreement | Prohibited |
| Delivery condition | As-rolled allowed | Declared R, N, Q, or M condition |
| Annex H sour service | No | Yes |
| Annex J offshore | No | Yes |
| Certification | Supplementary only | EN 10204 3.1 minimum |
| Marking | Grade, PSL, OD, WT | Grade, PSL, OD, WT, heat no, pipe no |
Need the correct PSL written into your RFQ?
Send the service conditions, grade, size range, and code basis. We can review whether the enquiry should stay at PSL1 or move to PSL2, Annex H, or Annex J.
Chemical Composition - PSL1 vs PSL2
PSL2 reduces phosphorus and sulfur, usually lowers carbon, requires silicon limits, and brings carbon equivalent control into the specification. That directly affects weldability, toughness, and consistency from heat to heat.
- Phosphorus: PSL1 max 0.030%, PSL2 max 0.025%.
- Sulfur: PSL1 max 0.030%, PSL2 max 0.015%.
- Silicon: largely open in PSL1, mandatory in PSL2.
- Carbon equivalent: not required in PSL1, mandatory in PSL2.
PSL1 Chemical Limits - Seamless Pipe, WT <= 25 mm
| Grade | C | Mn | P | S | V + Nb + Ti |
|---|---|---|---|---|---|
| B | 0.28 | 1.20 | 0.030 | 0.030 | <= 0.15 combined |
| X42 | 0.28 | 1.30 | 0.030 | 0.030 | <= 0.15 combined |
| X52 | 0.28 | 1.40 | 0.030 | 0.030 | <= 0.15 combined |
| X60 | 0.28 | 1.40 | 0.030 | 0.030 | As agreed |
| X65 | 0.28 | 1.40 | 0.030 | 0.030 | As agreed |
| X70 | 0.28 | 1.40 | 0.030 | 0.030 | As agreed |
PSL1 Chemical Limits - Welded Pipe, WT <= 25 mm
| Grade | C | Mn | P | S | V + Nb + Ti |
|---|---|---|---|---|---|
| B | 0.26 | 1.20 | 0.030 | 0.030 | <= 0.15 combined |
| X42 | 0.26 | 1.30 | 0.030 | 0.030 | <= 0.15 combined |
| X52 | 0.26 | 1.40 | 0.030 | 0.030 | <= 0.15 combined |
| X60 | 0.26 | 1.40 | 0.030 | 0.030 | As agreed |
| X65 | 0.26 | 1.45 | 0.030 | 0.030 | As agreed |
| X70 | 0.26 | 1.65 | 0.030 | 0.030 | As agreed |
PSL2 Chemical Limits - Normalized Delivery
| Grade | C | Si | Mn | P | S | CE IIW | CE Pcm |
|---|---|---|---|---|---|---|---|
| BN | 0.24 | 0.45 | 1.20 | 0.025 | 0.015 | 0.43 | 0.25 |
| X42N | 0.24 | 0.40 | 1.20 | 0.025 | 0.015 | 0.43 | 0.25 |
| X52N | 0.24 | 0.45 | 1.40 | 0.025 | 0.015 | 0.43 | 0.25 |
| X60N | 0.24 | 0.45 | 1.40 | 0.025 | 0.015 | As agreed | As agreed |
| X65N | 0.24 | 0.45 | 1.40 | 0.025 | 0.015 | As agreed | As agreed |
PSL2 Chemical Limits - Quenched and Tempered Delivery
| Grade | C | Si | Mn | P | S |
|---|---|---|---|---|---|
| BQ | 0.18 | 0.45 | 1.20 | 0.025 | 0.015 |
| X42Q | 0.18 | 0.45 | 1.20 | 0.025 | 0.015 |
| X52Q | 0.18 | 0.45 | 1.40 | 0.025 | 0.015 |
| X60Q | 0.18 | 0.45 | 1.40 | 0.025 | 0.015 |
| X65Q | 0.18 | 0.45 | 1.40 | 0.025 | 0.015 |
PSL2 Chemical Limits - Thermomechanical Delivery
| Seamless | |||||
|---|---|---|---|---|---|
| Grade | C | Si | Mn | P | S |
| BM | 0.12 | 0.45 | 1.20 | 0.025 | 0.015 |
| X42M | 0.12 | 0.45 | 1.30 | 0.025 | 0.015 |
| X52M | 0.12 | 0.45 | 1.40 | 0.025 | 0.015 |
| X60M | 0.12 | 0.45 | 1.40 | 0.025 | 0.015 |
| X65M | 0.12 | 0.45 | 1.60 | 0.025 | 0.015 |
| Welded | |||||
|---|---|---|---|---|---|
| Grade | C | Si | Mn | P | S |
| BM | 0.12 | 0.45 | 1.20 | 0.025 | 0.015 |
| X42M | 0.12 | 0.45 | 1.30 | 0.025 | 0.015 |
| X52M | 0.12 | 0.45 | 1.40 | 0.025 | 0.015 |
| X60M | 0.12 | 0.45 | 1.65 | 0.025 | 0.015 |
| X65M | 0.12 | 0.45 | 1.70 | 0.025 | 0.015 |
Carbon Equivalent - PSL2 Only
Carbon equivalent predicts field weldability. Higher CE raises the risk of hydrogen cracking in the heat-affected zone, which is why PSL2 brings formula-based control into the standard.
| Formula | Applies When | Calculation |
|---|---|---|
| CE IIW | C > 0.12% | C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15 |
| CE Pcm | C <= 0.12% | C + Si/30 + (Mn + Cu + Cr)/20 + Ni/60 + Mo/15 + V/10 + 5B |
Commercial reading
For Grade B through X52, API 5L fixes CE limits at CE IIW <= 0.43 and CE Pcm <= 0.25. For X60 and above, the CE ceiling should be written into the purchase specification instead of assumed.
Mechanical Properties - PSL1 vs PSL2
The mechanical difference is not just slightly different minimums. PSL2 also prevents overly hard pipe by imposing maximum yield and tensile values plus a maximum yield-to-tensile ratio.
PSL1 Mechanical Properties
| Grade | ISO 3183 | Min Yield MPa | Min Tensile MPa |
|---|---|---|---|
| B | L245 | 241 | 414 |
| X42 | L290 | 290 | 414 |
| X52 | L360 | 359 | 455 |
| X60 | L415 | 414 | 517 |
| X65 | L450 | 448 | 531 |
| X70 | L485 | 483 | 565 |
PSL2 Mechanical Properties
| Grade | Min Yield | Max Yield | Min Tensile | Max Tensile | Max Rt0.5/Rm |
|---|---|---|---|---|---|
| B | 245 | 450 | 415 | 655 | 0.93 |
| X42 | 290 | 495 | 415 | 655 | 0.93 |
| X52 | 360 | 530 | 460 | 760 | 0.93 |
| X60 | 415 | 565 | 520 | 760 | 0.93 |
| X65 | 450 | 600 | 535 | 760 | 0.93 |
| X70 | 485 | 635 | 570 | 760 | 0.93 |
Why maximum strength matters
Pipe that is too strong can become harder and less forgiving during field welding. PSL2 solves that by limiting yield and tensile strength and controlling the yield-to-tensile ratio.
Testing Requirements - PSL1 vs PSL2
This is usually where the commercial premium of PSL2 becomes most visible. Testing scope drives both mill workload and documentation depth.
Hydrostatic Testing
Both PSL1 and PSL2 require hydrostatic testing of every pipe. The major differences start after hydro.
Charpy V-Notch Impact Testing
| Aspect | PSL1 | PSL2 |
|---|---|---|
| Required | No, supplementary only | Yes for most grades |
| Locations | - | Body, weld seam, HAZ for welded pipe |
| Specimens | - | 3 per location |
| Test temperature | - | Project specified, often 0 C, -20 C, or -40 C |
| Shear area | - | >= 85% for PSL2 pipe at DN 500 and above |
Non-Destructive Testing
| Method | Applies To | PSL1 | PSL2 |
|---|---|---|---|
| UT full body | Seamless | Not required | Required |
| UT weld seam | ERW, SAW | Not required | Required |
| RT weld seam | SAW | Not required | Optional alternative to UT |
| MPI / ECT seam | ERW | As agreed | Required |
| UT strip / plate edge | SAW | Not required | Required |
ERW Frequency and Repair Rules
- PSL2 requires ERW welding frequency of at least 100 kHz.
- Low-frequency welded inventory cannot simply be re-certified to PSL2.
- PSL1 can allow weld repair by agreement.
- PSL2 prohibits weld repair to the pipe body, plate, or skelp.
PSL2 Delivery Conditions and Suffixes
PSL2 requires every pipe to be ordered and marked with a delivery condition. That condition signals the metallurgical route used to achieve the specified properties.
| Suffix | Condition | Description | Available For |
|---|---|---|---|
| R | As-rolled | No heat treatment after rolling | Grade B and X42 only |
| N | Normalized | Austenitized then air cooled | B through X65 |
| Q | Quenched and tempered | Quench followed by tempering | B through X65 |
| M | Thermomechanical | Controlled rolling below recrystallization | B through X80 |
Adding an S suffix, such as X65QS or X52MS, indicates Annex H sour service compliance. PSL1 does not offer this route.
Sour Service - PSL2 Only
Annex H aligns API 5L with sour service expectations used alongside NACE MR0175 / ISO 15156. If H2S is present, PSL2 is not optional.
| Additional Requirement | Details |
|---|---|
| HIC testing | NACE TM0284 hydrogen induced cracking resistance |
| SSC testing | NACE TM0177 where required for MS suffix |
| Maximum hardness | 250 HV10 for body, weld seam, and HAZ |
| Through-wall hardness survey | Required across the wall section |
| Additional chemistry control | Lower sulfur and improved inclusion shape control |
| Calcium treatment | Used for sulfide shape control and cleanliness |
Common sour suffixes are NS, QS, and MS. In practice, X65 remains the most common upper grade for serious sour service projects.
Sour service requirements by grade: Grade B, X42, X52, X60, X65.
Offshore Service - PSL2 Only
Annex J adds the offshore performance checks expected in subsea and deepwater pipeline work, typically alongside DNV rules and project-specific procedure qualification.
| Additional Requirement | Details |
|---|---|
| Through-thickness tensile testing | Supports biaxial loading checks during lay operations |
| Strain capacity testing | Confirms ductility for strain-based design |
| Enhanced CVN | Often extended to -40 C or -60 C |
| CTOD testing | Fracture mechanics validation for weld and HAZ |
| Enhanced NDT scope | Stricter coverage and acceptance criteria |
| Manufacturing Procedure Qualification | Pre-production approval of the whole process route |
The dominant offshore specification remains X65 PSL2 Annex J, usually in LSAW form for installation performance and traceability.
Traceability and Marking
| Aspect | PSL1 | PSL2 |
|---|---|---|
| Traceability scope | Heat number and test unit | Heat number, test unit, individual pipe number |
| Duration | Until testing is passed | Permanent after completion of all tests |
| Certification | Only when supplementary requirement is specified | Mandatory EN 10204 3.1 minimum |
| Marking Element | PSL1 | PSL2 |
|---|---|---|
| API specification number | Yes | Yes |
| Grade | Yes | Yes |
| PSL level | Yes | Yes |
| OD and WT | Yes | Yes |
| Manufacturing method | Yes | Yes |
| Heat number | Optional | Yes |
| Pipe number | Not required | Yes |
| Test pressure | Yes | Yes |
Size Range and Pipe End Differences
| PSL1 | PSL2 | |
|---|---|---|
| Minimum OD | 0.405 in (10.3 mm) | 2.375 in (60.3 mm) |
| Maximum OD | 80 in | 80 in |
| Pipe End Type | PSL1 | PSL2 |
|---|---|---|
| Plain end | Yes | Yes |
| Beveled end | Yes | By supplementary requirement in practice |
| Threaded end | Yes | No |
| Special coupling | Yes | No |
PSL2 does not cover very small diameters below 2.375 in OD. That limitation matters when someone expects small-bore pipe to be upgraded to PSL2 after manufacture.
When to Specify PSL1
PSL1 remains commercially valid when all of the following are true:
- The design code does not require CVN impact testing.
- The line is not exposed to H2S.
- The service is not offshore.
- Full traceability to individual pipe is not required.
- The service is general utility, municipal water, low-pressure gas, or non-critical process duty.
Typical PSL1 applications include municipal water transmission, low-pressure gas distribution, structural piling, and general plant utility piping.
Commercial point
PSL1 is often 5% to 10% lower in unit cost because it avoids mandatory CVN, mandatory NDT, tighter chemistry control, and controlled delivery condition requirements.
When to Specify PSL2
PSL2 becomes mandatory as soon as one major risk driver enters the project.
- Offshore pipeline or subsea installation -> specify PSL2 and evaluate Annex J.
- H2S exposure or sour environment -> specify PSL2 and evaluate Annex H.
- Design code requires impact testing -> specify PSL2.
- Project specification or EPC standard says PSL2 -> specify PSL2.
- Transmission service in X52 and above -> PSL2 is normally the market standard.
Typical PSL2 applications include oil and gas transmission, offshore pipelines, sour service pipelines, high-pressure gas trunk lines, and low-temperature or arctic pipeline service.
How MetalFromTurkey Supplies PSL1 and PSL2 Pipe
MetalFromTurkey sources both PSL1 and PSL2 pipe through API-capable Turkish mill partners across seamless, ERW, LSAW, and SSAW manufacturing routes. The practical value is not only the mill source, but the ability to line up production route, inspection scope, documentation, and third-party review to the project requirement.
| Document | Reference |
|---|---|
| Mill Test Certificate | EN 10204 Type 3.1 standard, 3.2 on request |
| CVN test results | Per project-specified temperature |
| NDT reports | ISO 10893 series, UT / RT / MPI / ECT as applicable |
| Chemical analysis certificate | Heat analysis and product analysis when required |
| Dimensional report | OD, WT, and length checks by production lot |
Project review support
We can compare PSL1 vs PSL2, Annex H vs standard PSL2, and LSAW vs seamless routes before the RFQ is finalized.
Inspection coordination
SGS, Bureau Veritas, TUV, and Lloyd's attendance can be aligned with mill schedules before production starts.
Localized follow-up
Use this guide together with our API 5L line pipe page and the grade pages for B, X42, X52, X60, and X65.
Need API 5L Pipe
Quoted Correctly?
Send the service conditions, target grade, dimensions, and required PSL level. We will align the mill route and document package to your enquiry.
Common Questions
What does PSL stand for in API 5L?
PSL stands for Product Specification Level. API 5L defines two levels: PSL1 (standard quality) and PSL2 (enhanced quality). PSL is not a grade. It is a quality tier applied on top of grades such as B, X42, X52, X60, X65, and X70. There is no PSL3 in the API 5L standard.
What is the main difference between PSL1 and PSL2?
PSL2 has stricter chemical limits, mandatory Charpy V-Notch impact testing, mandatory NDT, full traceability to individual pipe, maximum yield and tensile strength limits, and exclusive access to sour service (Annex H) and offshore (Annex J) annexes. PSL1 specifies only minimum mechanical requirements and does not require impact testing, NDT, or full traceability.
Is PSL2 better than PSL1?
PSL2 is not better. It is more stringent. For critical-service pipelines such as offshore, sour service, and high-pressure transmission, PSL2 is required. For general utility service, water distribution, and low-pressure gas, PSL1 can be adequate at lower cost.
Can PSL1 pipe be upgraded to PSL2 after production?
No. PSL2 requirements must be controlled during manufacturing, including chemistry targets, delivery condition, NDT scope, and traceability. A PSL1 pipe cannot simply be retested and upgraded to PSL2 after production.
Is Annex H available under PSL1?
No. Sour service Annex H is available only under PSL2.
Is Annex J available under PSL1?
No. Offshore Annex J is available only under PSL2.
How much more does PSL2 usually cost?
PSL2 pipe typically costs 5% to 10% more than PSL1 of the same grade and size. The premium covers mandatory CVN testing, NDT, enhanced documentation, controlled delivery conditions, and tighter chemical requirements.
Does PSL2 always require heat treatment?
PSL2 requires a declared delivery condition for every pipe. As-rolled delivery is only permitted for Grade B and X42. For X52 and above, PSL2 pipe is typically supplied in N, Q, or M condition.