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0102030405
Welded Steel Pipes for Low-Pressure Fluid Conveyance - China Suppliers & Factory for GB/T 3091-2015 Standards
Ordering Information
Buyers should specify in contracts:
- Standard number (GB/T 3091-2015)
- Steel grade (e.g., Q195, Q215A/B, Q235A/B, Q265A/B, Q295A/B, Q345A/B)
- Dimensions (outer diameter, wall thickness, length)
- Surface treatment (galvanized or black)
- Special requirements (e.g., hydrostatic testing, non-destructive testing)
Main Steel Grades & Chemical/Mechanical Properties
🔩 Steel Grades
- Non-galvanized pipes: Q195, Q215A/B, Q235A/B, Q265A/B, Q295A/B, Q345A/B
- Galvanized pipes: Typically use Q195–Q345 grades
⚙️ Key Requirements
- Chemical composition: Limits for C, Mn, Si, S, P, etc., vary by grade
- Mechanical properties: Tensile strength, yield strength, and elongation comply with grade-specific values (e.g., Q235: yield strength ≥235 MPa)
Q195
Q215A/B
Q235A/B
Q265A/B
Q295A/B
Q345A/B
Manufacturing Process
- Pipes are welded via high-frequency resistance welding (ERW) or other welding methods.
- Galvanized pipes undergo hot-dip galvanizing (zinc coating ≥500 g/m² for DN≥100 mm).
Inspection Requirements
1 Dimensional Tolerances
- Outer diameter, wall thickness, and length must meet specified limits.
2 Mechanical Tests
- Tensile test, flattening test, bending test (for pipes ≤DN50 mm), and hydrostatic test (or non-destructive testing).
3 Surface Quality
- No cracks, laps, or harmful defects. Galvanized pipes must have a continuous, adherent zinc layer.
4 Hydrostatic Test
- Test pressure = 5 MPa (or 2.5 MPa for galvanized pipes); held for ≥5 sec without leakage.
5 Non-Destructive Testing (NDT)
- Alternative to hydrostatic testing; methods include eddy current or ultrasonic testing.
Marking & Certification
- Each pipe must be marked with: manufacturer's name, steel grade, size, standard number, and inspection mark.
- A quality certificate must accompany deliveries, including test results.
Comparison with Previous Versions
GB/T 3091-2015 replaces the 2008 version, with updates to:
- Expanded steel grades (added Q265, Q295, Q345)
- Clarified inspection rules for galvanized pipes
- Enhanced NDT requirements
🏗️ Key Applications
Widely used in construction, plumbing, firefighting, and low-pressure gas/water supply systems.
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❓ Frequently Asked Questions (FAQ)
Q What standard governs low-pressure fluid transport steel pipes in China?
GB/T 3091-2015 is the governing Chinese national standard for welded steel pipes used in low-pressure fluid transport, including water, gas, and heating applications. It replaced the previous GB/T 3091-2008 version with expanded grades and stricter inspection rules.
Q What steel grades are available under GB/T 3091-2015?
Available grades include Q195, Q215A/B, Q235A/B, Q265A/B, Q295A/B, and Q345A/B for non-galvanized pipes. Galvanized pipes typically use grades within the Q195–Q345 range. The 2015 revision added Q265, Q295, and Q345 grades compared to the 2008 version.
Q What is the difference between galvanized and non-galvanized (black) steel pipes?
Non-galvanized (black) pipes are bare steel pipes suitable for applications where corrosion resistance is not critical. Galvanized pipes are coated with a zinc layer via hot-dip galvanizing, providing enhanced corrosion resistance. For pipes with DN≥100 mm, the zinc coating must be ≥500 g/m².
Q What tests are required for GB/T 3091-2015 pipes?
Required tests include dimensional tolerance checks, tensile testing, flattening testing, bending testing (for pipes ≤DN50 mm), and either hydrostatic testing (5 MPa for black pipes, 2.5 MPa for galvanized, held ≥5 seconds) or non-destructive testing (eddy current or ultrasonic methods).
Q What information must be included when ordering GB/T 3091-2015 pipes?
Purchase contracts should specify the standard number (GB/T 3091-2015), steel grade, outer diameter, wall thickness, pipe length, surface treatment (galvanized or black), and any special requirements such as hydrostatic or non-destructive testing.
Q What are the main applications of GB/T 3091-2015 welded steel pipes?
These pipes are widely used across construction, plumbing, firefighting systems, and low-pressure gas and water supply networks. Their versatility across both galvanized and non-galvanized forms makes them suitable for a broad range of infrastructure and industrial projects.