City gas pipelines include main gas transmission pipelines, distribution pipelines, user introduction pipes, and indoor gas pipelines, each of which has a different purpose. According to the different gas transmission pressure, it can be divided into low pressure (not higher than 0.01MPa), medium pressure (0.01~0.4MPa), sub-high pressure (0.4~1.6MPa), and high pressure (1.6~4.0MPa). Generally speaking, the higher the pipeline pressure, the greater the possibility of pipeline leakage, and the higher the quality requirements for the pipeline; but the use of higher-pressure pipelines can reduce the initial investment of the entire pipeline network. Pipes with different purposes, different pressures, and different diameters must have different materials and different processes.
In the urban gas pipeline network, steel pipes are generally used for high-pressure, sub-high-pressure pipelines, and main gas transmission pipes, but there are also problems with the selection of steel pipe types. In recent years, straight-seam welded steel pipes have shown a tendency to gradually replace spiral pipes in pipelines with higher pressure. At present, the price of high-frequency electric resistance welded (ERW) steel pipe is lower than that of spiral pipe, and its quality and reliability are higher than that of spiral pipe. It has a good cost performance and is more and more widely used. There is a method in which the outer diameter of the pipe is ￠≤406mm, using straight seam resistance welding ERW steel pipe, and ￠>406mm using straight seam double-sided submerged arc welding steel pipe (UOE forming process).
In terms of medium and low-pressure pipelines, PE pipes have good flexibility, corrosion resistance, and smooth inner walls, making PE80 PE pipes the main pipe material for small-diameter medium and low-pressure gas pipeline networks. In foreign countries, the high-density PE100 material PE pipe has become the first choice for buried medium and low-pressure gas pipelines due to its incomparable advantages in price and maintenance costs [1]. However, when the diameter of the pipe is larger than the economic limit diameter of the PE pipe, the steel pipe should be used. For example, medium-pressure pipelines above DN200 mainly use straight seam resistance welded ERW steel pipes.
In the city, the population accumulates, the vehicles are concentrated, there are many construction areas, and the underground facilities are complicated. The environment of the gas pipeline is special, so higher requirements are put forward for the selection of the pipeline. Straight-seam steel pipes should be used in key areas to reduce the length of pipe welds, improve the quality of welds, and reduce the possibility of accidents. In addition, when determining the steel grade of the pipeline, it should be lowered by one level based on the steel grade selected according to the economic ratio, to increase the wall thickness of the pipeline and improve the linear stiffness of the pipeline.
City gas pipelines include main gas transmission pipelines, distribution pipelines, user introduction pipes, and indoor gas pipelines, each of which has a different purpose. According to the different gas transmission pressure, it can be divided into low pressure (not higher than 0.01MPa), medium pressure (0.01~0.4MPa), sub-high pressure (0.4~1.6MPa), and high pressure (1.6~4.0MPa). Generally speaking, the higher the pipeline pressure, the greater the possibility of pipeline leakage, and the higher the quality requirements for the pipeline; but the use of higher-pressure pipelines can reduce the initial investment of the entire pipeline network. Pipes with different purposes, different pressures, and different diameters must have different materials and different processes.
In the urban gas pipeline network, steel pipes are generally used for high-pressure, sub-high-pressure pipelines, and main gas transmission pipes, but there are also problems with the selection of steel pipe types. In recent years, straight-seam welded steel pipes have shown a tendency to gradually replace spiral pipes in pipelines with higher pressure. At present, the price of high-frequency electric resistance welded (ERW) steel pipe is lower than that of spiral pipe, and its quality and reliability are higher than that of spiral pipe. It has a good cost performance and is more and more widely used. There is a method in which the outer diameter of the pipe is ￠≤406mm, using straight seam resistance welding ERW steel pipe, and ￠>406mm using straight seam double-sided submerged arc welding steel pipe (UOE forming process).
In terms of medium and low-pressure pipelines, PE pipes have good flexibility, corrosion resistance, and smooth inner walls, making PE80 PE pipes the main pipe material for small-diameter medium and low-pressure gas pipeline networks. In foreign countries, the high-density PE100 material PE pipe has become the first choice for buried medium and low-pressure gas pipelines due to its incomparable advantages in price and maintenance costs [1]. However, when the diameter of the pipe is larger than the economic limit diameter of the PE pipe, the steel pipe should be used. For example, medium-pressure pipelines above DN200 mainly use straight seam resistance welded ERW steel pipes.
In the city, the population accumulates, the vehicles are concentrated, there are many construction areas, and the underground facilities are complicated. The environment of the gas pipeline is special, so higher requirements are put forward for the selection of the pipeline. Straight-seam steel pipes should be used in key areas to reduce the length of pipe welds, improve the quality of welds, and reduce the possibility of accidents. In addition, when determining the steel grade of the pipeline, it should be lowered by one level based on the steel grade selected according to the economic ratio, to increase the wall thickness of the pipeline and improve the linear stiffness of the pipeline.
Post time: Jun-27-2023