Selection of submerged arc steel pipe:
1. For pipelines with high requirements for peak regulation, due to the uneven gas consumption of users and frequent fluctuations in pipeline pressure, the alternating stress on the steel pipe is very large, and the existing defects in the pipe will expand under the alternating stress. If you choose For spiral welded steel pipes with many welds and a high probability of defects, the operation of the pipeline will not be guaranteed.
2. The pipeline crosses the seismic fault zone or passes through the local high-intensity earthquake area. Due to the frequent geological activities in these areas, 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 submerged arc steel pipes. Under long-term stress, the accident probability of spiral welded steel pipes is much higher than that of submerged arc steel pipes. Therefore, submerged arc steel pipes should be used in this area.
3. Submerged arc steel pipes should be used for pipelines with high requirements for internal and external anti-corrosion layers. Spiral submerged arc welded steel pipes have more weld passes, and the weld reinforcement is generally higher than that of submerged arc steel pipes. When the steel pipes are internally and externally anti-corrosion, the combination of anti-corrosion materials and bare pipes is not as tight as submerged arc steel pipes, and the anti-corrosion effect is not as good as submerged arc steel pipes. The steel pipe is good.
4. For important crossing projects, submerged arc steel pipes should be used. Since future maintenance and management are more difficult than general line sections, it is especially advantageous to use high-performance submerged arc steel pipes.
5. For the weak link of the pipeline, such as the hot-simmered elbow pipe, the submerged arc steel pipe should be used. Due to the change of direction, the hot-simmering elbow bears greater internal and external forces than the straight pipe section of the general line. Due to the influence of various factors during the simmering process, its stress is not easy to eliminate, and it is a relatively weak link in the long-distance pipeline. , the use of submerged arc steel pipes with good comprehensive performance can make up for these deficiencies.
Submerged arc steel pipe production process:
Straight seam steel pipe is a steel pipe whose weld seam is parallel to the longitudinal direction of the steel pipe. It is usually divided into metric electric welded steel pipe, electric welded thin-walled pipe, transformer cooling oil pipe, and so on. The production process of straight seam steel pipe is simple, the production efficiency is high, the cost is low, and the development is rapid. The strength of the spiral welded pipe is generally higher than that of the straight seam welded pipe, and the welded pipe with a larger diameter can be produced with a narrower billet, and welded pipes with different diameters can be produced with the same width billet. But compared with the straight seam pipe of the same length, the weld length is increased by 30~100%, and the production speed is lower. Plate inspection: After the steel plate used to manufacture large-diameter submerged arc steel pipes enters the production line, the whole plate wave inspection is carried out; edge milling: the two edges of the steel plate are milled on both sides by the edge milling machine to make it reach the required plate width and plate edges are parallel degree and groove shape; pre-bending: use the pre-bending machine to pre-bend the edge of the plate, so that the edge of the plate has a curvature that meets the requirements; forming: half of the pre-bent steel plate is stamped multiple times on the JCO forming machine , press into a J shape, and then bend the other half of the steel plate into a C shape, and finally form an open O shape; pre-welding: make the formed straight seam welded steel pipe seam and use gas shielded welding (MAG) for continuous Welding; internal welding: use tandem multi-wire submerged arc welding (mostly four wires) to weld on the inside of the straight seam steel pipe; external welding: use tandem multi-wire submerged arc welding to weld on the outside of the submerged arc steel pipe; wave test Ⅰ : 100% inspection of the inner and outer welds of straight seam welded steel pipes and the base metal on both sides of the welds; X-ray inspection Ⅰ: 100% inspection of the inner and outer welds by X-ray industrial television, using an image processing system to ensure the accuracy of flaw detection Sensitivity; expand the diameter of the full length to improve the dimensional accuracy of the steel pipe, and check the distribution state of the internal stress of the 50# steel plate; hydrostatic test: inspect the expanded steel pipes one by one on the hydraulic testing machine to ensure that the steel pipe meets the standard requirements Test pressure, the machine has automatic recording and storage functions; chamfering: process the pipe end of the steel pipe after inspection to meet the required pipe end groove size; wave inspection II: conduct wave inspection one by one again to check the straight seam welding Possible defects of steel pipes after diameter expansion and water pressure; X-ray inspection II: X-ray industrial TV inspection and pipe end weld seam filming of steel pipes after diameter expansion and water pressure test; pipe end magnetic particle inspection: carry out this inspection To find the pipe end defects; anti-corrosion and coating: qualified steel pipes are anti-corrosion and coating according to user requirements.
Post time: Aug-04-2023