Reassessing the Issue of Long Welds in Spiral Steel Pipes
2022-05-07
For a long time, there has been ongoing debate over whether spiral‑welded pipes or straight‑seam pipes—particularly in comparison with UOE‑type pipes—are superior. As spiral‑welded pipe manufacturing technology has advanced to its present state, we should conduct a proper evaluation and comparison, and reassess the issue of the relatively longer weld seams in spiral‑welded pipes. First of all, because defects are typically oriented parallel to the weld seam, the weld‑related flaws in spiral‑welded pipes are classified as “oblique defects.”
Leaving aside how spiral steel pipes are used by industry professionals, some customers and others may still feel uncertain. Therefore, we’re sharing key usage guidelines for spiral steel pipes online, with the entire team at the spiral steel pipe manufacturer eager to collaborate and provide this information. After all, understanding proper application of spiral steel pipes is essential.
The weld seam of a spiral‑welded steel pipe is longer than that of a straight‑seam pipe; if the pipe length is L, the weld length is L cos θ. For a long time, there has been ongoing debate over whether spiral‑welded pipes or straight‑seam pipes—particularly UOE‑type pipes—are superior. With the advancement of spiral‑welded pipe manufacturing technology to its current state, we should conduct a proper evaluation and comparison, and reassess the issue of the relatively longer weld seam in spiral‑welded pipes. First, because defects are parallel to the weld seam, the weld‑related defects in spiral‑welded pipes are classified as “oblique defects.”
During service, the principal stress direction in spiral-welded pipe—i.e., the axial direction of the pipe—results in a smaller equivalent defect length compared to that in longitudinal-seam pipe. Furthermore, since pipeline steels are all produced from rolled plates, their impact toughness exhibits significant anisotropy: the CVN value measured along the rolling direction can be up to three times higher than that measured perpendicular to the rolling direction.
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