Comparison of spiral pipe and LSAW steel pipe

(1) Spiral steel pipe manufacturing process determines its residual stress is large, according to foreign data, some even close to the yield limit, straight submerged arc welded steel pipe due to the pipe expansion process, the residual stress is close to zero.
(2) Spiral weld welding tracking and ultrasonic online testing tracking are more difficult, therefore, the probability of exceeding the weld defects is higher than the straight submerged arc welded pipe.
(3) Spiral steel pipe weld misalignment mostly in 1.1 ~ 1.2 mm, in accordance with international practice, the amount of misalignment to be less than 10% of the thickness, such as pipe wall thickness is small, the amount of misalignment is difficult to meet the requirements of the straight submerged arc welded pipe without this problem.
(4) Compared with the straight submerged arc welded pipe, the spiral weld line is poor, the stress concentration phenomenon is serious.
(5) Spiral submerged arc welded steel pipe heat-affected zone is greater than the heat-affected zone of straight submerged arc welded steel pipe, and the heat-affected zone is the weak link in the quality of welded pipe.
(6) Spiral seam welded steel pipe geometry accuracy is poor, to the field construction (such as alignment, welding) to bring some difficulties.
(7) The same diameter, spiral seam welded steel pipe can achieve a thickness much smaller than the LSAW steel pipe.