STRENGTH CHARACTERISTICS OF SPIRAL WELDED PIPE

When the pipe is subjected to internal pressure, there are two kinds of main stress, i.e., the radial stress Y and the axial stress X. Weld stress 1/2 = Y (l/4sin2 alpha +cos2 alpha), where the alpha helix angle of the spiral welded pipe.

Spiral welded pipe seam angle is 50-75 degrees, so the stress synthesis of spiral weld seam welded pipe is principal stress 60-85%. In the same work under pressure, with a diameter ratio of spiral welded pipe welded pipe wall thickness can be reduced.

According to the above characteristics can be known:

1. Spiral welded pipe blasting occurs when the weld under normal stress and compound stress is relatively small, the blasting is generally not originated in the spiral seam, the safety of welded pipe high ratio.

2. When there is a defect in the vicinity of the spiral weld, due to the small force of the spiral weld, the risk of expansion is not as large as that of the straight weld.

3. Since the radial stress is the maximum stress on the steel pipe, the weld is subjected to the maximum load in the direction of the vertical stress. The maximum load of longitudinal and circumferential weld load minimum between spiral seam between the two.