Current Edition: GB/T 3091-2022 (Replaces GB/T 3091-2015)
Published by: Standardization Administration of China (SAC)
Overview
GB/T 3091 (Welded Steel Pipes for Low-Pressure Fluid Conveyance) is a Chinese national standard that specifies the technical requirements for welded steel pipes used to transport water, air, gas, oil, and other low-pressure fluids in civil, industrial, and mechanical applications.
These pipes are commonly used in:
Building water supply and fire protection systems
HVAC (Heating, Ventilation, and Air Conditioning)
Structural scaffolding and handrails
Agricultural irrigation
Low-pressure oil and gas pipelines (non-critical)
The standard applies to straight seam welded steel pipes manufactured by high-frequency resistance welding (HFW/ERW). It includes requirements for dimensions, weight, technical delivery conditions, testing, and marking.
✅ GB/T 3091 is the most widely used standard for general-purpose welded steel pipes in China and many international markets.
Scope
|
Parameter |
Description |
|
Pipe Type |
Electric Resistance Welded (ERW), Straight Seam |
|
Manufacturing Process |
High-Frequency Resistance Welding (HFW) |
|
Diameter Range |
DN6 to DN600 (NPS 1/8" to 24") |
|
Wall Thickness |
Light, standard, and heavy gauge options |
|
End Types |
Plain ends, threaded ends (with or without couplings), beveled ends |
|
Coating Options |
Black (uncoated), hot-dip galvanized (most common), varnish-coated |
Note: The standard does not apply to high-pressure, high-temperature, or sour (H₂S) service environments.
Material Grades (Steel Types)
The base steel material typically conforms to GB/T 3094 or GB/T 1591, and common grades include:
|
Grade |
Equivalent |
Description |
|
Q195 |
Low-carbon steel |
Low strength, suitable for small-diameter pipes |
|
Q215 |
Low-carbon steel |
General-purpose, moderate strength |
|
Q235 |
ASTM A53 Grade A/B, S235JR |
Most widely used; good weldability and formability |
|
Q355 |
S355JR, ASTM A500 |
Higher strength for structural use |
✅ Pipes are often marked with the steel grade, e.g., Q235B, indicating quality level B.
Key Technical Requirements
|
Requirement |
Description |
|
Welding |
Longitudinal seam; no filler metal; full fusion |
|
Heat Treatment |
Not required for Q195–Q235; normalization may be required for Q355 |
|
Dimensional Tolerances |
Strict limits on outer diameter (OD), wall thickness, straightness, and ovality |
|
Hydrostatic Test |
Required for all pipes unless exempted (e.g., galvanized pipes may be tested before galvanizing) |
|
Non-Destructive Testing (NDT) |
100% Eddy Current Testing (ECT) or Ultrasonic Testing (UT) on the weld seam |
|
Galvanizing (if applicable) |
Must comply with GB/T 13912 – Metal Coatings – Hot Dip Galvanized Coatings on Iron and Steel Articles |
|
- Coating Mass |
≥ 300 g/m² (average), ≥ 275 g/m² (local) for DN ≤ 50 mm; higher for larger pipes |
|
- Appearance |
Uniform, smooth, no bare spots, excessive dross, or flux residues |
|
Mechanical Properties |
Tensile strength, yield strength, and elongation tested per batch |
|
Bending Test |
Required for pipes with DN ≤ 65 mm to ensure weld integrity |
Marking and Packaging
Each pipe must be clearly marked with:
- Manufacturer's name or trademark
- Standard number: GB/T 3091
- Pipe size (DN or OD × WT)
- Steel grade (e.g., Q235B)
- Manufacturing date or batch number
- "Galvanized" or "Zn" if coated
Packaging: Bundled with steel strips, protected ends, suitable for sea or land transport.
Common Applications
|
Industry |
Application |
|
Construction |
Water supply, fire sprinkler systems, scaffolding |
|
Municipal |
Urban water distribution networks |
|
HVAC |
Heating and cooling pipelines |
|
Agriculture |
Irrigation systems |
|
Industrial |
Low-pressure air, oil, and gas lines |
Comparison with Other Standards
|
Standard |
Application |
Notes |
|
GB/T 3091 |
Low-pressure fluid transport |
ERW, galvanized common |
|
GB/T 9711 |
Pipeline transport (oil/gas) |
Equivalent to API 5L, higher pressure |
|
API 5L |
Line pipe |
International standard, higher performance |
|
ASTM A53 |
Structural & fluid service |
Closest international equivalent to GB/T 3091 |
|
BS 1387 |
UK standard for water/gas |
Similar scope, now largely superseded |
ASTM A53 Grade B is often considered the closest international equivalent to GB/T 3091 Q235.
Summary Table
|
Feature |
Specification |
|
Standard |
GB/T 3091-2022 |
|
Pipe Type |
ERW (HFW), straight seam |
|
Size Range |
DN6 – DN600 (1/8" – 24") |
|
Common Grades |
Q195, Q215, Q235, Q355 |
|
Coating |
Black or hot-dip galvanized |
|
Testing |
Hydrotest, ECT/UT, tensile, bend |
|
Ends |
Plain, threaded (with coupling), beveled |
|
Application |
Low-pressure fluid, structural, fire protection |
