(1) For pipelines with high peaking requirements, the user's gas consumption is very uneven, the pipeline pressure fluctuates frequently, and the alternating stress of the steel pipe is large. The existing defects in the pipe will expand under the alternating stress. The use of spiral welded steel pipes with many welds and high probability of defects will not guarantee the operation of the pipeline.
(2) The pipeline crosses the seismic fault zone or passes through the local high-intensity seismic zone. Due to the frequent geological activities of these sections, longitudinal or axial alternating stress will be generated on the pipeline. There are many spiral welds and the probability of defects is higher than that of
straight seam submerged arc welded steel tubes. Under long-term stress, the probability of accidents in spiral welded steel pipes is much higher than that of straight seam submerged arc welded steel pipes. Therefore, straight lines should be used in this area. Submerged arc welded steel pipe.
(3) For pipes with high requirements for internal and external anti-corrosion coatings, straight seam submerged arc welded steel pipes shall be used.
Spiral submerged arc welded steel pipe has many weld beads. The weld bead height is generally higher than that of straight seam submerged arc welded steel pipe. When the inner and outer anticorrosion of the steel pipe is carried out, the combination of anticorrosive material and bare pipe is not as tight as that of straight seam submerged arc welded steel pipe. The anti-corrosion effect is also good without straight seam submerged arc welded steel pipe.
(4) For important piercing projects, straight seam submerged arc welded steel pipes should be used. Since the maintenance management in the future is more difficult than the general line segment, it is especially suitable for the straight seam submerged arc welded steel pipe with excellent performance.
(5) For weak pipelines, such as hot elbow pipe, straight seam submerged arc welded steel pipe shall be used. Due to the change of direction, the internal and external forces of the hot elbow are larger than the straight pipe sections of the general line. Because of the various factors in the tanning process, the stress is not easily eliminated, which is a relatively weak link in the long-distance pipeline. The use of straight seam submerged arc welded steel pipe with comprehensive performance can make up for these shortcomings.
