What is a straight seam welded pipe?
Straight seam welded pipe is a steel pipe with a straight weld seam parallel to the longitudinal direction of the steel pipe, also known as a straight seam steel pipe, which is made by bending a steel plate or strip and then welding the joints. The production process of straight seam welded pipe is simple, the wall thickness is uniform, the production efficiency is high, the cost is low, and its specification can be adjusted flexibly to meet the requirements of different pipe diameters, so it develops rapidly and is often used in various industrial production and urban pipeline construction. According to the production process of straight seam steel pipe, it can be divided into two types: high frequency straight seam steel pipe (ERW steel pipe) and submerged arc welding straight seam steel pipe (LSAW steel pipe).
In recent years, most oil and gas pipelines in the world have required the use of straight seam welded pipes. Western developed countries such as Canada improve the process of spiral welded pipes, such as pre-welding, fine welding, multi-wire welding and mechanical expansion, etc.
They are all designed with reference to the technology of straight seam submerged arc welded pipe, reflecting the advancement and superiority of the control technology of straight seam welded pipe.
Specifically: From the perspective of being suitable for offshore oil and gas transportation, it is necessary to construct longitudinal welded pipes. At present, a considerable part of the world's oil and gas resources are buried in the ocean. From the perspective of future natural gas development, they are mainly buried in the ocean in the form of "combustible ice". It is currently recognized that the total energy of "combustible ice" is 2-3 times that of all coal, oil, and gas, and it is the same in China, and it will be the main energy source in the future.
Recently, China is accelerating the pace of oil and gas in the East China Sea. With the development of oil exploration to the depths of the ocean, the submarine pipeline is crushed under the joint action of pressure, impact and bending force, which is the weak link of the spiral welded pipe. In order to improve the transportation capacity of the pipeline and make the submarine pipeline develop in the direction of thick wall, the submarine pipeline mostly adopts the straight seam welded pipe.
From another point of view, due to the difficulty of butt welding of pipelines in the ocean, high requirements are required for the ellipticity, alignment, groove protection and cross-section error of the steel pipe, otherwise the operation efficiency will be seriously affected. Therefore, compared with spiral welded pipes, longitudinal welded pipes have higher dimensional accuracy and easier repair welding. So from this aspect, straight seam welded pipe is also the first choice.
Coal slurry and ore slurry pipelines are required to use straight seam welded pipes. The pipeline conveys "paste" coal and mineral powder in the upward direction. Since the weld reinforcement in the spiral welded pipe is a spiral line, the resistance to the coal slurry is large, and the pipeline needs a larger wall thickness, so the straight seam welded pipe is preferred.
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