GB/T 9711.1 Spiral Welded Steel Pipe (SSAW)
Basic Overview
GB/T 9711.1 is the Chinese national standard titled "Petroleum and natural gas industries - Steel pipe for pipelines - Technical delivery conditions - Part 1: Pipes of requirement class A" . This standard specifically applies to spiral submerged arc welded (SSAW) steel pipes used in oil and gas transmission systems .
This is the Class A (PSL1 equivalent) quality level – the standard quality level for pipeline transportation systems, with basic requirements suitable for general service applications .
Name Explanation
| Part | Meaning |
|---|---|
| GB/T | Chinese national standard (Guobiao/Tuijian) |
| 9711.1 | Standard number for petroleum and natural gas industry pipelines - Part 1 |
| Class A | Requirement class A (equivalent to API 5L PSL1) – standard quality level |
| SSAW | Spiral Submerged Arc Welding – pipe formed from steel coil with continuous spiral seam; double-sided automatic submerged arc welding |
Key Specifications
| Attribute | Description |
|---|---|
| Standard | GB/T 9711.1 (current version: GB/T 9711.1-2023; previous: GB/T 9711.1-2011/1997) |
| Quality Level | Class A (PSL1 equivalent) – standard quality, basic requirements |
| Application | Oil and gas transmission pipelines; conveying combustible and non-combustible fluids (including water) |
| Steel Grades (L-series) | L175, L210, L245, L290, L320, L360, L390, L415, L450, L485, L555 and intermediate grades |
| 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; up to 4064 mm available |
| Wall Thickness | 5 mm to 32 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)
The "L" designation stands for "Line pipe". The number indicates minimum yield strength in MPa :
| Grade | Minimum Yield Strength (MPa) | Minimum Tensile Strength (MPa) | Equivalent API 5L Grade | Typical Application |
|---|---|---|---|---|
| L175 | 175 | 315 | - | Very low-pressure gathering |
| L210 | 210 | 335 | A | Low-pressure water, gas, general service |
| L245 | 245 | 415 | B | General pipeline service - MOST COMMON |
| L290 | 290 | 415 | X42 | Medium-pressure transmission |
| L320 | 320 | 435 | X46 | Medium-pressure transmission |
| L360 | 360 | 460 | X52 | General transmission |
| L390 | 390 | 490 | X56 | Higher-pressure transmission |
| L415 | 415 | 520 | X60 | High-pressure transmission |
| L450 | 450 | 535 | X65 | High-pressure, offshore |
| L485 | 485 | 570 | X70 | Long-distance high-pressure |
| L555 | 555 | 625 | X80 | Ultra-high-pressure trunk lines |
Note: L245 is the most commonly used grade for general pipeline service .
Chemical Composition (Typical for L245 - PSL1 equivalent)
| Element | Maximum % | Notes |
|---|---|---|
| Carbon (C) | 0.22-0.26% | Low carbon for good weldability |
| Manganese (Mn) | 0.90-1.20% | Provides strength |
| Silicon (Si) | 0.35-0.45% | Deoxidizer |
| Phosphorus (P) | 0.030% | Controlled for weldability |
| Sulfur (S) | 0.030% | Controlled for toughness |
Note: Class A (PSL1) has no requirement for maximum yield strength, carbon equivalent, or mandatory impact testing .
Mechanical Properties (Typical for L245 - PSL1 equivalent)
| Property | Requirement |
|---|---|
| Yield Strength (min) | 245 MPa |
| Tensile Strength (min) | 415 MPa |
| Elongation | Per GB/T 9711.1 formula (varies by wall thickness) |
| Charpy Impact | Not required for Class A – only Class B (PSL2) requires mandatory impact testing |
Dimensional Tolerances (GB/T 9711.1)
| Parameter | Size Range | Tolerance |
|---|---|---|
| Outside Diameter (D < 508mm) | - | ±0.75% D |
| Outside Diameter (D ≥ 508mm) | - | ±1.00% D |
| Wall Thickness (D < 508mm) | - | +15% / -12.5% of nominal |
| Wall Thickness (D ≥ 508mm) | - | +17.5% / -10% of nominal |
| Straightness | All sizes | ≤ 0.2% of total length |
| Length (fixed) | - | +100mm / -0mm |
Typical Size Availability (SSAW):
| OD (inch) | OD (mm) | Wall Thickness Range (mm) |
|---|---|---|
| 16" | 406 | 5.0 - 14.0 |
| 20" | 508 | 5.0 - 16.0 |
| 24" | 610 | 5.0 - 18.0 |
| 30" | 762 | 6.0 - 22.0 |
| 36" | 914 | 6.0 - 25.0 |
| 40" | 1016 | 6.0 - 26.0 |
| 48" | 1219 | 8.0 - 28.0 |
| 56" | 1422 | 8.0 - 30.0 |
| 60" | 1524 | 8.0 - 30.0 |
| 64" | 1626 | 8.0 - 32.0 |
| 72" | 1829 | 8.0 - 32.0 |
SSAW Manufacturing Process
Spiral welded pipes under GB/T 9711.1 are produced using the following process :
| Step | Description |
|---|---|
| 1. Raw Material Preparation | Hot-rolled steel coils meeting chemistry requirements are leveled and edge-milled |
| 2. Edge Preparation | Strip edges are milled for proper welding |
| 3. Spiral Forming | Steel strip is continuously formed into a cylindrical shape at a specific helix angle at room temperature |
| 4. Submerged Arc Welding | Double-sided automatic submerged arc welding (inside and outside) creates the spiral seam with full penetration |
| 5. Non-Destructive Testing | 100% ultrasonic or X-ray inspection of the weld seam |
| 6. Hydrostatic Testing | Each pipe individually tested |
| 7. Finishing | End processing, beveling, coating, and marking according to specifications |
Testing & Inspection Requirements (Class A / PSL1)
| Test Type | Requirement | Notes |
|---|---|---|
| Chemical Analysis | Per heat lot | Verifies composition limits per GB/T 9711.1 |
| Tensile Test | Per lot | Verifies yield and tensile strength |
| Flattening Test | Required | Checks ductility and weld integrity |
| Bend Test | Required | Verifies weld integrity |
| Charpy Impact Test | Not required for Class A | Only Class B (PSL2) requires mandatory impact testing |
| Hydrostatic Test | Each pipe | Pressure integrity verification |
| Ultrasonic Inspection | 100% of weld seam | Standard practice for SSAW |
| X-ray Inspection | For critical applications | Available upon request |
| Dimensional Inspection | 100% | Per GB/T 9711.1 tolerances |
| Mill Test Certificate | Provided | With full test results |
Class A (PSL1) vs. Class B (PSL2) Comparison
| Feature | Class A (GB/T 9711.1) | Class B (GB/T 9711.2) |
|---|---|---|
| Quality Level | Standard (PSL1 equivalent) | Enhanced (PSL2 equivalent) |
| Carbon (C) max | Higher limits | Tighter controls |
| Sulfur (S) max | 0.030% | 0.015% (50% reduction) |
| Yield Strength | Minimum only | Minimum and maximum specified |
| Yield-to-Tensile Ratio | Not specified | ≤ 0.93 |
| Impact Testing | Not required | Mandatory |
| NDT Requirements | Standard | More stringent |
| Traceability | Batch level | Pipe-by-pipe |
| Typical Use | General service, water lines, non-critical | Critical service, sour service, low temperature |
Common Applications
| Application | Description |
|---|---|
| Oil and Gas Transmission | Long-distance pipelines for crude oil, natural gas, and refined products |
| Natural Gas Gathering | Connecting wells to processing facilities |
| Water Transmission | Municipal and industrial water pipelines |
| Gathering Lines | Upstream oil and gas operations |
| Structural Applications | Piling, bridge supports, construction |
| Industrial Process Piping | Refineries, chemical plants, power generation |
Advantages of SSAW under GB/T 9711.1
| Advantage | Description |
|---|---|
| Large Diameter Capability | SSAW produces pipes from 8" to 142"+ OD – ideal for large-diameter transmission pipelines |
| Cost-Effective | More economical than LSAW or seamless for large diameters |
| Long Lengths | Up to 32 m lengths reduce field welding requirements |
| High Weld Integrity | Double-sided welding creates a single high-quality weld nugget |
| 100% NDT | Mandatory ultrasonic or X-ray inspection of weld seam ensures quality |
| Wide Grade Range | L175 through L555 – equivalent to API 5L A through X80 |
| International Compatibility | Technically aligned with API 5L PSL1 |
| Proven Performance | Used in major projects including West-East Gas Pipeline |
Coating Options
GB/T 9711.1 SSAW pipes can be supplied with various coatings for corrosion protection :
| Coating Type | Best For | Key Features |
|---|---|---|
| 3LPE (3-layer polyethylene) | Buried pipelines | Most common; excellent corrosion protection, high impact resistance |
| FBE (Fusion Bonded Epoxy) | Oil & gas pipelines | Strong adhesion, chemical resistance |
| Coal Tar Epoxy | Marine environments | Heavy-duty protection |
| Varnish / Anti-rust oil | Temporary protection | Short-term corrosion protection during transport |
| Bitumen Coating | Buried service | Cost-effective protection |
| Black Oil Coating | Standard mill finish | Temporary protection |
GB/T 9711.1 vs. Other Chinese Standards
| Standard | Application | Quality Level | Key Difference |
|---|---|---|---|
| GB/T 9711.1 | Oil and gas pipelines | Class A (PSL1) | For pipeline transportation systems |
| GB/T 9711.2 | Oil and gas pipelines | Class B (PSL2) | Enhanced requirements, mandatory impact testing |
| GB/T 3091 | Low-pressure fluid transmission | General | Water, air, steam – lower pressure rating |
| SY/T 5037 | Low-pressure fluid pipelines | General | Petroleum industry standard for low pressure |
| GB/T 14291 | Mine fluid service | General | Mining applications (slurry, dewatering) |
Important Considerations
1. Class A (PSL1) vs. Class B (PSL2)
Class A (9711.1) : Standard quality – no mandatory impact testing, minimum strength only
Class B (9711.2) : Enhanced quality – mandatory impact testing, maximum strength limits, tighter chemistry
2. Grade Nomenclature
L-series (e.g., L245, L360) is used in GB/T 9711
Equivalent API 5L grades: L245 = Grade B, L360 = X52, L415 = X60, L485 = X70
3. Impact Testing
Class A (9711.1) does not require Charpy impact testing by the standard
For low-temperature service, specify Class B (GB/T 9711.2) instead
4. Standard Versions
GB/T 9711.1 has been updated over the years (1997, 2011, 2017, 2023 versions)
Current version: GB/T 9711.1-2023
When ordering, specify the required version year
5. Third-Party Inspection
Available inspection services include SGS, BV, Lloyds
Summary
GB/T 9711.1 Spiral Submerged Arc Welded (SSAW) steel pipe is the Chinese national standard for Class A (PSL1 equivalent) line pipe used in oil and gas transmission systems. With steel grades from L175 through L555 (equivalent to API 5L A through X80) and diameters from 219 mm to 3620 mm (8" to 142"), this standard covers large-diameter pipelines for medium to high-pressure transmission applications.
Key features:
Standard: GB/T 9711.1 – Chinese national standard for oil and gas pipelines
Quality Level: Class A (PSL1 equivalent) – standard quality for general service
Grades: L175 through L555 – equivalent to API 5L A through X80
L245 (Grade B) is the most common grade for general pipeline service
SSAW manufacturing produces pipes from 8" to 142" OD with wall thickness up to 32 mm
Double-sided welding creates a single high-quality weld nugget
100% ultrasonic inspection of weld seam ensures quality
No mandatory impact testing for Class A – suitable for ambient temperature applications
Technically aligned with API 5L PSL1 – internationally compatible
Common applications include:
Oil and gas transmission pipelines
Natural gas gathering and distribution networks
Water transmission mains
Gathering and flow lines
Structural applications (piling, bridge supports)
When ordering, specify: GB/T 9711.1, Grade (e.g., L245), SSAW (spiral submerged arc welded), Size (OD x WT), Length, End Finish (plain/beveled), Coating Requirements, Standard Version (e.g., GB/T 9711.1-2023), and Mill Test Certificate.
For applications requiring guaranteed low-temperature toughness, tighter chemistry controls, or sour service capability, specify GB/T 9711.2 (Class B/PSL2) instead .
