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0102030405
China Welded Steel Pipes for Low-Pressure Fluid Transport - Suppliers & Factory Available
Ordering Information
Buyers should specify in contracts the following details to ensure accurate order fulfillment:
▸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 Q195, Q215A/B, Q235A/B, Q265A/B, Q295A/B, Q345A/B
▸Galvanized 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 the following updates:
▸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 the low-pressure fluid transmission welded steel pipes described here?
These pipes are manufactured and inspected in accordance with GB/T 3091-2015, which is the current Chinese national standard for low-pressure fluid transmission welded steel pipes, replacing the previous 2008 version.
Q What steel grades are available for both galvanized and non-galvanized pipes?
Non-galvanized pipes are available in grades Q195, Q215A/B, Q235A/B, Q265A/B, Q295A/B, and Q345A/B. Galvanized pipes typically use grades within the Q195–Q345 range, selected based on application requirements.
Q What is the minimum zinc coating thickness required for galvanized pipes?
For galvanized pipes with nominal diameter DN≥100 mm, the hot-dip zinc coating must be at least 500 g/m². The zinc layer must be continuous and well-adhered, with no cracks or peeling.
Q What information must buyers specify when placing an order?
Buyers must specify the standard number (GB/T 3091-2015), desired steel grade, dimensions (outer diameter, wall thickness, length), surface treatment (galvanized or black), and any special requirements such as hydrostatic or non-destructive testing.
Q Can non-destructive testing (NDT) replace the hydrostatic pressure test?
Yes. According to GB/T 3091-2015, NDT methods such as eddy current or ultrasonic testing are accepted as alternatives to the hydrostatic test. Buyers may specify their preferred testing method in the contract.
Q What are the typical applications of these welded steel pipes?
These pipes are widely used in construction, plumbing, firefighting systems, and low-pressure gas and water supply networks. Their versatility, combined with availability in both galvanized and black finishes, makes them suitable for a broad range of infrastructure projects.