Pipeline Works
- Carbon & Carbon Alloy Steel
- Stainless Steel
- Copper & Nickel Alloy
- Heat Efficiency Tubes
- Pipe Fittings
- Pipe Flanges
- Gasket, Stud Bolt &Nut
- Industrial Valves
01
GB/T 3091-2015 Standard - Welded Steel Pipes for Low-pressure Fluid Conveyance
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).
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.
Want to order the same ? Contact us Now to send your request!
