Weld angle of spiral welded pipe.

The helix angle of the spiral steel pipe weld is generally 50-75 degrees, so the synthetic stress at the spiral weld is 60-85% of the principal stress of the straight seam welded pipe. Under the same working pressure, the wall thickness of spiral steel pipes with the same diameter can be smaller than that of straight seam welded pipes.

Conclusion

According to the above characteristics, we can know:

1. When a spiral welded pipe explodes, since the normal stress and synthetic stress on the weld are relatively small, the blast hole generally does not originate from the spiral weld, and its safety is higher than that of straight seam welded pipes.
2. When there are parallel defects near the spiral weld, the risk of expansion of the spiral weld is not as great as that of the straight weld because the force on the spiral weld is smaller.
3. Since radial stress is the maximum stress existing on the steel pipe, the weld will bear the maximum load when it is in the direction of vertical stress. That is, the straight seam bears the largest load, the circumferential weld bears the smallest load, and the spiral seam is between the two.