1. Question: How do you ensure the integrity and strength of the weld seam in your ERW pipes?
Answer: Weld integrity is our top priority. We employ a multi-layered quality assurance system. First, during production, we utilize state-of-the-art high-frequency welding with strict control over annealing temperatures to refine the grain structure of the weld. Second, we perform 100% Non-Destructive Testing (NDT) using an online Ultrasonic Tester (UT) or Eddy Current Tester. Finally, for critical orders, we conduct destructive tests like Flattening, Flare, and Guided Bend tests on samples from each heat lot to physically validate the weld strength against the base metal.
2. Question: What Non-Destructive Testing (NDT) methods do you use to detect weld defects?
Answer: To guarantee a flawless weld, we employ a combination of online NDT methods. Primarily, we use an Ultrasonic Tester (UT) to scan the entire weld seam and the Heat Affected Zone (HAZ) for internal discontinuities. In parallel, we use an Eddy Current Tester (ET) to detect surface and near-surface defects. For high-pressure service pipes, we also offer the option of Full Body Ultrasonic Testing upon request.
3. Question: Do you perform Hydrostatic Testing on every single pipe? What are the test parameters?
Answer: Yes, absolutely. 100% of our ERW pipes undergo a rigorous Hydrostatic Testing process as a final check for leaks and weld strength. The pipe is filled with water, and internal pressure is applied according to the specified standard (e.g., API 5L or ASTM A53). The pressure is held for a minimum of 5 to 10 seconds to ensure there is no drop in pressure or visible leakage. We can provide the hydrostatic test reports with the specific pressure value applied, which is calculated based on the pipe's dimensions and grade.
4. Question: How do you control the "Flash" (weld bead) inside the pipe? Is it removed?
Answer: Control of the internal weld flash (the excess metal squeezed out during welding) is critical for flow efficiency. In our standard production, the external flash is always trimmed flush. For the internal flash, we have two options:
Standard: Internal flash is controlled but not removed (a small bead remains).
Internal Flash Trimmed (IFT): We can install tooling to cut the internal weld bead down to a very low profile, or flush with the pipe wall. This is highly recommended for applications where internal cleaning pigs will be used or where maximum flow area is needed. Please specify if you require IFT.
5. Question: What is the "Heat Affected Zone" (HAZ) and why is it important in ERW pipes?
Answer: The Heat Affected Zone (HAZ) is the area of the base metal adjacent to the weld that has had its microstructure and mechanical properties altered by the heat of welding. In ERW pipes, a narrow HAZ is a sign of a good, efficient weld. A wide HAZ can indicate excessive heat input, which might make the pipe more brittle in that region. Our high-frequency welding process is precisely controlled to minimize the HAZ, ensuring that the mechanical properties across the weld area remain as close as possible to the parent metal, which we verify through our hardness testing procedures.
