50 to 60 years, spiral steel pipe(SSAW steel pipe) in the oil and gas pipelines in the widely used, 70 to 80 years by the LSAW steel pipes and ERW steel pipes of serious challenges, since the world is basically in the oil and gas pipeline is no longer used in the spiral steel.
Division and has not allowed oil and gas pipeline companies use spiral submerged arc welded steel pipe. This is because the development of the steel pipe industry reliability requirements are high, spiral steel pipe manufacturer itself can not overcome its shortcomings, making it difficult to meet the objective requirements of the development.
LSAW steel pipes with spiral in quality compared to some deficiencies, the following summary of a seven for your reference.
(1) spiral steel pipe manufacturing process determine the residual stress is large, as far as foreign to historical records, some even close to the yield limit, LSAW steel pipe due to the use of extended techniques, residual stress close to zero.
(2) spiral seam weld line tracking and detection of ultrasonic tracking than difficult, therefore, the probability of higher than excessive weld defects LSAW pipe.
(3) the amount of spiral steel pipe weld the wrong side of the majority of the 1.1 ~ 1.2 mm, in accordance with international practice, the amount is less than the thickness of the wrong side of 10%, such as pipe wall thickness is small, the wrong side of the volume is difficult to meet the requirements, and straight seam submerged arc pipe is no such problem.
(4), compared with LSAW pipe, spiral weld flow line is poor, serious stress concentration
(5) spiral submerged arc welded steel pipe heat-affected zone than LSAW steel pipe heat affected zone, and the quality of welded heat-affected zone is the weak link.
(6) spiral seam welded steel pipe geometry accuracy, to the construction site (such as the counterpart, welding) to bring some difficulties.
(7) the same diameter, spiral seam welded steel pipe can achieve far less than the thickness of LSAW steel pipes.
