GB/T 9711.2 Spiral Welded Steel Pipe (SSAW)
Basic Overview
GB/T 9711.2 is the Chinese national standard that specifies PSL 2 (Product Specification Level 2) requirements for steel pipes used in petroleum and natural gas pipeline transportation systems . This standard covers spiral submerged arc welded (SSAW) steel pipes for demanding applications requiring enhanced quality, including high-pressure transmission, low-temperature service, and sour service environments .
Critical Understanding: GB/T 9711.2 is not a standalone document. It must be used together with GB/T 9711.1 (General requirements) to form a complete specification for PSL 2 SSAW pipes .
Standard Structure
| Part | Title | Application |
|---|---|---|
| GB/T 9711.1 | General requirements | Base requirements for all pipes (covers SSAW in general) |
| GB/T 9711.2 | PSL 2 requirements | Additional enhanced requirements for PSL 2 |
| GB/T 9711.3 | PSL 3 requirements | Highest quality level (rarely used) |
Usage Rule: GB/T 9711.1 + GB/T 9711.2 = Complete specification for PSL 2 SSAW pipes .
Key Specifications
| Attribute | Description |
|---|---|
| Standard | GB/T 9711.2 (current version: GB/T 9711.2-2023; previous: GB/T 9711.2-2011/1999) |
| Quality Level | PSL 2 (Product Specification Level 2) – enhanced quality for critical service |
| Application | High-pressure oil and gas transmission; sour service; low-temperature service |
| Steel Grades | L245 through L555 (equivalent to API 5L Grade B through X80) |
| Manufacturing Process | Spiral Submerged Arc Welding (SSAW) – double-sided automatic submerged arc welding |
| Size Range (SSAW) | 219 mm to 3620 mm (approx. 8" to 142") OD |
| Wall Thickness | 5 mm to 26 mm (common range 5-26 mm) |
| Length | 6 m to 18 m standard; up to 32 m available |
| End Finishes | Plain ends, beveled ends (30° bevel angle) |
Steel Grades (L-Series) - PSL 2
| Grade | Min Yield (MPa) | Max Yield (MPa) | Min Tensile (MPa) | Equivalent API 5L |
|---|---|---|---|---|
| L245 | 245 | 450 | 415 | Grade B |
| L290 | 290 | 495 | 415 | X42 |
| L320 | 320 | 525 | 435 | X46 |
| L360 | 360 | 530 | 460 | X52 |
| L390 | 390 | 545 | 490 | X56 |
| L415 | 415 | 565 | 520 | X60 |
| L450 | 450 | 600 | 535 | X65 |
| L485 | 485 | 635 | 570 | X70 |
| L555 | 555 | 705 | 625 | X80 |
Note: Suffix letters (M, N, Q) indicate heat treatment condition (M = TMCP, N = Normalized, Q = Quenched & tempered).
PSL 2 vs. PSL 1 Comparison
| Feature | PSL 1 (GB/T 9711.1) | PSL 2 (GB/T 9711.2) | Significance |
|---|---|---|---|
| Quality Level | Standard | Enhanced | Higher reliability |
| Chemistry Control | Standard limits | Tighter limits (C ≤ 0.12-0.22%, S ≤ 0.015%) | Better weldability, HIC resistance |
| Yield Strength | Minimum only | Minimum and maximum specified | Prevents over-strength materials |
| Yield-to-Tensile Ratio | Not specified | ≤ 0.93 | Ensures adequate ductility |
| Impact Testing | Not required | Mandatory at specified temperature | Guarantees low-temperature toughness |
| NDT Requirements | Standard | 100% comprehensive (RT/UT) | Better defect detection |
| Hydrostatic Test | 90% SMYS | 95% SMYS with longer hold time | Higher pressure verification |
| Traceability | Batch level | Pipe-by-pipe full traceability | Complete quality documentation |
Chemical Composition (PSL 2 SSAW)
| Grade | C max | Si max | Mn max | P max | S max |
|---|---|---|---|---|---|
| L245M (Grade B) | 0.22 | 0.45 | 1.20 | 0.025 | 0.015 |
| L290M (X42M) | 0.22 | 0.45 | 1.30 | 0.025 | 0.015 |
| L360M (X52M) | 0.22 | 0.45 | 1.40 | 0.025 | 0.015 |
| L415M (X60M) | 0.12 | 0.45 | 1.60 | 0.025 | 0.015 |
| L450M (X65M) | 0.12 | 0.45 | 1.60 | 0.025 | 0.015 |
| L485M (X70M) | 0.12 | 0.45 | 1.70 | 0.025 | 0.015 |
| L555M (X80M) | 0.12 | 0.45 | 1.85 | 0.025 | 0.015 |
*Note: Higher grades (X60-X80) have significantly lower carbon content for better weldability .*
Impact Test Requirements (PSL 2)
| Grade | Test Temperature | Minimum Average Energy | Specimen Location |
|---|---|---|---|
| L245NB | -10°C | 27 J | Weld & HAZ |
| L360NB | -10°C | 40 J | Weld & HAZ |
| L415NB | -10°C | 45 J | Weld & HAZ |
| L450NB | -10°C | 50 J | Weld & HAZ |
| L485NB | -10°C | 60 J | Weld & HAZ |
Dimensional Tolerances (PSL 2)
| Parameter | Tolerance | Measurement Method |
|---|---|---|
| Outside Diameter | ±0.5% or ±3mm | Circumference tape |
| Wall Thickness | +10% / -5% | Ultrasonic gauge, 4 points per pipe |
| Ovality | ≤ 1.0% of OD | Max-min diameter |
| Straightness | ≤ 0.15% of length | Straight edge |
| Length (fixed) | +100mm / -0mm | Tape measure |
| End Squareness | ≤ 1.6mm | Square tool |
SSAW Manufacturing Process (PSL 2)
Spiral welded pipes under GB/T 9711.2 are produced with enhanced quality controls :
| Step | Description | PSL 2 Specific Requirements |
|---|---|---|
| 1. Material Traceability | Each plate/coil individually identified | Full traceability from heat to pipe |
| 2. Edge Preparation | Strip edges milled for proper welding | Precision edge milling |
| 3. Spiral Forming | Continuous spiral forming at room temperature | Strict dimensional control |
| 4. Submerged Arc Welding | Double-sided automatic SAW (inside + outside) | Welding procedures must be qualified |
| 5. Weld Repair | Limited repairs allowed | Max 2 repairs per weld |
| 6. NDT Inspection | 100% radiographic (RT) and/or ultrasonic (UT) | Full weld length inspection |
| 7. Hydrostatic Testing | 95% SMYS, ≥30 seconds hold | Higher pressure than PSL 1 |
| 8. Finishing | End beveling, coating, marking | Enhanced marking requirements |
Non-Destructive Testing (PSL 2)
| NDT Method | Coverage | Acceptance Criteria |
|---|---|---|
| Radiographic (RT) | 100% weld length | Cracks not permitted |
| Ultrasonic (UT) | 100% weld length | Lack of fusion ≤12.5mm length |
| Visual (VT) | 100% surface | Smooth weld transition |
| Magnetic Particle (MT) | All repairs | No linear defects |
Weld Bead Profile Requirements (PSL 2)
| Parameter | Internal Weld | External Weld |
|---|---|---|
| Reinforcement Height | 0-2.5mm | 0-3.0mm |
| Undercut | ≤ 0.5mm depth | ≤ 0.8mm depth |
| Overlap | Not permitted | Not permitted |
Common Applications
| Application | Description |
|---|---|
| High-Pressure Gas Transmission | Long-distance natural gas pipelines |
| Crude Oil Trunk Lines | Main transmission lines for crude oil |
| Offshore Pipelines | Subsea pipelines requiring high strength-to-weight ratio |
| Sour Service | H₂S environments (with supplementary NACE requirements) |
| Low-Temperature Service | Arctic and cold climate pipelines |
| Regulated Pipelines | FERC, DOT, FEMSA compliance |
Quality Documentation (PSL 2)
| Document | Content Required |
|---|---|
| Mill Certificate (Type 3.1) | Full chemical, mechanical, NDT results |
| Welding Documents | WPS, PQR, WPQ |
| NDT Records | RT films, UT scans, reports |
| Hydrostatic Test | Pressure-time charts |
| Traceability Records | Heat to pipe mapping |
| Repair Records | All repair documentation |
Marking Requirements (PSL 2)
| Information | Marking Method |
|---|---|
| Manufacturer | Stencil/paint near pipe end |
| Standard | "GB/T 9711.2" |
| Grade | e.g., "L485M" |
| PSL Level | "PSL 2" |
| Heat Number | Unique ID |
| Pipe Number | Sequential |
| Test Pressure | Actual value MPa |
Advantages of GB/T 9711.2 SSAW Pipe
| Advantage | Description |
|---|---|
| Enhanced Quality | PSL 2 provides guaranteed low-temperature toughness and stricter controls |
| High Strength | Grades up to L555 (X80) with 555 MPa minimum yield |
| Large Diameter Capability | SSAW produces pipes from 8" to 142" OD |
| 100% NDT | Mandatory radiographic or ultrasonic inspection of weld seam |
| Full Traceability | Pipe-by-pipe traceability for complete quality documentation |
| Sour Service Capable | Available with HIC/SSC testing for H₂S environments |
| International Compatibility | Technically aligned with API 5L PSL 2 |
Important Considerations
1. GB/T 9711.2 is NOT Standalone
This standard must be used together with GB/T 9711.1. Complete specification = GB/T 9711.1 + GB/T 9711.2 .
2. PSL 2 vs. PSL 1 Selection
PSL 2: Required for low-temperature service, sour service (H₂S environments), regulated pipelines, and critical applications
PSL 1: Suitable for general service, water lines, non-critical applications
3. Sour Service Requirements (Optional)
For H₂S environments, specify additional requirements :
HIC Test per NACE TM0284 (CLR ≤ 15%, CTR ≤ 5%)
SSC Test per NACE TM0177 (No cracking at 90% AYS)
Hardness ≤ 250 HV10
4. Grade Nomenclature
Suffix letters indicate heat treatment condition:
M: Thermomechanical rolled (TMCP) – most common for SSAW
N: Normalized
Q: Quenched and tempered
S: Sour service
5. Third-Party Inspection
Available inspection services include SGS, BV, Lloyds
6. Standard Versions
Current version: GB/T 9711.2-2023
Previous versions: GB/T 9711.2-2011, GB/T 9711.2-1999
Summary
GB/T 9711.2 Spiral Submerged Arc Welded (SSAW) steel pipe is the Chinese national standard for PSL 2 (enhanced quality) line pipe used in critical oil and gas transmission applications. With steel grades from L245 through L555 (equivalent to API 5L Grade B through X80), this standard covers large-diameter pipelines requiring guaranteed low-temperature toughness, tighter chemistry controls, and full traceability.
Key features:
Standard: GB/T 9711.2 – PSL 2 requirements for oil and gas pipelines
Quality Level: PSL 2 – enhanced quality for critical service
Grades: L245 through L555 – equivalent to API 5L Grade B through X80
SSAW manufacturing produces pipes from 8" to 142" OD with wall thickness up to 26 mm
Double-sided welding creates a single high-quality weld nugget
100% NDT (RT/UT) of weld seam mandatory
Mandatory impact testing at specified temperature (typically -10°C)
Stricter chemical controls – carbon ≤ 0.12-0.22%, sulfur ≤ 0.015%
Maximum strength limits prevent over-strength materials
Full traceability from steelmaking to finished pipe
Common applications include:
High-pressure gas transmission pipelines
Offshore and subsea pipelines
Sour service applications (with supplementary NACE requirements)
Low-temperature and arctic pipelines
Regulated pipelines (FERC, DOT, FEMSA)
When ordering, specify: GB/T 9711.1 + GB/T 9711.2, Grade (e.g., L485M), SSAW (spiral submerged arc welded), Size (OD x WT), Length, End Finish (plain/beveled), Coating Requirements, Impact Test Temperature, and Mill Test Certificate (EN 10204 Type 3.1). For sour service applications, specify additional HIC/SSC testing per NACE MR0175 .
