(1) For the requirement of high peak load of pipeline, because the gas consumption of users is very uneven, the pressure fluctuation in pipeline is frequent, and the alternating stress steel can withstand larger pipeline, the existing alternating stress defects will be enlarged. If more weld defects are selected, the safe operation of pipeline will not be guaranteed.
(2) Pipeline crosses seismic faults or local high seismic areas. Because of frequent geological activities in these areas, the pipeline will produce alternating vertical or axial stresses. Spiral weld is much higher than the probability of defects of LSAW steel pipe. Under long-term stress, the probability of accidents of spiral welded steel pipe is much higher than that of LSAW steel pipe. Therefore, DSAW pipe should be used in such areas.
(3) Internal and external coatings require high-level management to use LSAW. The weld seam of spiral submerged arc welded pipe is generally higher than that of LSAW. When the steel pipe is corroded inside and outside, the combination of anticorrosive material and bare pipe is not as close as LSAW, and the anticorrosive effect of LSAW pipe is not good.
(4) For important wear and tear in engineering, use LSAW. Because the future maintenance and management is more difficult than the general line segment, the use of LSAW's superior performance is particularly necessary.
(5) LSAW should be used for pipeline defects, such as hot and ironing elbows. Since the direction of hot-ironing elbow is changed, the contact force between them is larger than that of straight pipeline. Because of various factors, it is not easy to eliminate stress in the ironing process. It is a long-weak link distance pipeline. LSAW with good comprehensive performance can make up for these shortcomings.