When large diameter spiral welded pipe bursting occurs, the blasting mouth generally does not originate in the spiral weld, its safety is Longitudinal because the small weld suffered stress and the resultant stress.

But regardless of the yield stress still bursting pressures were lower than the Longitudinal spiral welded pipe.

According to the test indicate the relevant U.S. research institutions, spiral welded pipe and Longitudinal course with a level, but the spiral welded pipe has a high impact toughness. Moreover, according to the submerged arc welding process delineated each weld shall have the extinction of the arc, but each ring in the welding seam welded pipe, can not reach the premise, and there are many welding defects. In an interview with the internal pressure of the pipe, usually, two main stress on the wall, that radial, and axial stress. Followed by increasing the diameter of the pipe, and the steel grade of progress, the greater the occurrence of ductile fracture tip steady expansion trend.

Withstand the maximum load because the radial stress is the maximum stress on the large diameter spiral pipe, the weld in vertical stress in this direction. According to the measurement results, the fatigue strength of the spiral welded pipe and seamless steel pipe, and ERW pipe is the same test data with seamless and unified resistance tubes distributed in the region and higher than the average.

Large diameter spiral welded steel pipe welds degree helix angle is generally, therefore spiral weld resultant stress is bursting reason. The longitudinal principal stress test also shows the mouth of the ring spiral welded pipe bursting was significantly greater than the rate of deformation Longitudinal. From the welding process, the welding and spiral welded pipe joints straight consistent approach, but inevitably there will be many chances Longitudinal seam of T, so there is also greatly improved weld defects and weld seam at T residual stress is large, often in the weld metal three-dimensional stress state, increasing the likelihood of occurrence of cracks. That is the biggest bear the load straight seam, circumferential welds to withstand the load, and the spiral in between. When there are defects in parallel with large diameter spiral pipe welds around, because of the smaller spiral weld force, the risk of expansion is as good as straight weld large. It is evident that spiral welded plastic deformation capability than Longitudinal, blasting mouth generally confined to a pitch, which is the extension of the spiral weld to rip from a strong binding effect due.

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