Pipe under internal pressure, usually on the wall there are two main stress, namely the radial stress delta Y and delta X axial stress. Synthetic stress of the weld of the delta delta Y = (l / 4 sin2 alpha + cos2 alpha) 1/2, among them, the alpha for spiral welded pipe weld spiral Angle.
Weld spiral Angle of SSAW
is generally 50-75 degrees, so the spiral seam synthesis stress is straight seam welded pipe 60-85% of principal stress. Under the same working pressure, spiral welded pipe of the same diameter than the wall thickness can reduce the straight seam welding.
According to the above characteristics:
A. spiral welded tube blasting occurs, due to the weld is smaller, the normal stress and synthetic stress by blasting mouth does not generally originated in the spiral seam, its security is higher than straight seam welded pipe.
B. when screw near the weld are in parallel with the defect, due to the spiral weld stress is small, so its extension risk than straight weld.
C. because the radial stress is exist in the maximum stress on steel tube, so the weld in the vertical stress direction under maximum load. The straight seam under load, the largest ring to carry the load a minimum seamComputer Technology Articles, spiral seam between the two.