Testing Methods for Spiral Tube Manufacturing Processes

Release date:

2021-02-16

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Steel Pipe Knowledge

Spiral pipes, also known as spiral steel pipes or spiral welded pipes, are manufactured by rolling low-carbon structural steel or low-alloy structural steel strips into a tubular blank at a specific helical angle—referred to as the forming angle—and then welding the seam. This process enables the production of large-diameter steel pipes from relatively narrow steel strips. So, what are the manufacturing processes and inspection methods for spiral pipes? Let’s take a look.

　　 Spiral tube Also known as spiral steel pipe or spiral welded pipe, it is manufactured by rolling low-carbon structural steel or low-alloy structural steel strip into a tubular blank at a specific helical angle—referred to as the forming angle—and then welding the seam. This process enables the production of large-diameter steel pipes from relatively narrow steel strips. So, what are the manufacturing processes and inspection methods for spiral pipes? Let’s take a look.

　　The manufacturing processes for ordinary spiral pipes can be categorized into cold drawing and hot rolling. The cold‑rolled spiral steel pipe process is generally more complex than the hot‑rolled one. First, the billet undergoes continuous three‑roll rolling; after forming, it must pass a diameter‑control test. If no surface cracks are detected, the pipe is cut to approximately one meter in length using a cutting machine. It then enters the annealing stage, which requires pickling; during pickling, it is essential to inspect the surface for numerous blisters. If many blisters are present, the spiral steel pipe fails to meet quality standards. Visually, cold‑rolled spiral steel pipes are shorter than hot‑rolled ones, and their wall thickness is typically thinner as well.

　　However, it appears brighter than thick-walled spiral steel pipe, with a smoother surface and fewer burrs at the pipe ends. Hot‑rolled spiral steel pipes are typically delivered in their heat‑treated condition; after passing quality inspection, they must undergo rigorous manual sorting by qualified personnel.

　　Spiral tube inspection method:

　　After quality inspection, the steel pipe surface shall be coated with a layer of oil, followed by several cold-drawing tests. After hot rolling, a piercing test shall be conducted; if the piercing diameter exceeds the specified limit, straightening and correction are required. Following straightening, the pipes are transferred by handling equipment to the nondestructive testing (NDT) unit for NDT inspection, after which they are labeled and tagged in accordance with standards before being stored.

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