pipeline

Materials with metallurgical properties for the production of straight-seam submerged-arc welded steel, as well as for the production of spiral welded pipes and hot-rolled coils. Through advantages such as hot continuous rolling, high-quality steel is produced, leveraging advanced metallurgical processing capabilities. For example, a water cooling system is installed on the output station to accelerate cooling, allowing the use of low-alloy components in order to achieve a specific strength level and low-temperature toughness, thereby improving the weldability of the steel. But a basic steel production plant. The alloy content (carbon equivalent) of the coil is usually lower than that of steel plates of similar grades, which also improves the weldability of the spiral welded pipe. It should be noted that, since the rolling direction of the coil in spiral welded pipes is not perpendicular to the pipe axis (depending on the solution for the fold at the helix angle), whereas the rolling direction of the steel plates in straight-seam pipes is perpendicular to the pipe axis, the crack resistance of spiral welded pipe materials is superior to that of straight-seam pipes. •Welding processes involve the methods used to weld spiral welded pipes and straight-seam steel pipes; however, longitudinal welding often results in numerous T-joints, which increases the likelihood of welding defects. Moreover, due to the residual stresses associated with T-joint welding, the welded metal is typically in a three-dimensional stress state, thereby increasing the risk of cracks. According to the requirements of each welding process in submerged arc welding, the arc should be extinguished at each longitudinal weld seam; if this condition cannot be met, it may result in welding defects. •Strength properties refer to the internal pressure that a pipe can withstand, typically the two principal stresses on the wall: the radial stress ΔY and the axial stress δX. The stress generated by welding is δ=ΔY(1/4sin2α+cos2α)1/2, where α is the helix angle of the spiral welded pipe. The helix angle of spiral welded pipes is generally 50–75 degrees; therefore, the stress generated in the spiral weld accounts for 60–85% of the longitudinal principal stress. Under the same working pressure, the wall thickness of straight-seam welded steel pipes can be reduced. Based on these characteristics, it is said that: the pressure exerted on spiral welded pipes during explosion welding is relatively low, and the rupture point generally does not originate from the spiral weld, resulting in good longitudinal safety. B. For defects that are parallel to and located near the spiral weld, the stress on the spiral weld is lower; therefore, the risk of expansion is not as great as that in the case of straight welds. C. Since radial stress is the maximum stress in the pipe, the normal stress in this direction is highest at the weld under maximum load. It bears the loads applied to the circumferential weld seam, as well as the loads between the spirals. •The hydraulic bursting strength was verified through comparative tests, showing that the measured bursting pressure of spiral welded pipes at their longitudinal yield pressure is within a small deviation from the theoretical value. However, both the yield pressure and the burst pressure are lower for spiral welded pipes compared to straight-seam welded pipes. Blasting tests also showed that the circumferential deformation rate at the blast site of spiral welded pipes is significantly higher than that in the longitudinal direction; the plastic deformation at the blast site of such pipes is generally confined to one pitch, with the expansion of the spiral weld being limited by strong constraints. •Toughness and fatigue strength: The development trend for these pipelines is larger diameters and higher strength. As the pipe diameter increases and the steel grade rises, there is a tendency for the tip of the ductile fracture to expand steadily, thereby increasing in size. According to tests conducted by relevant American research institutions, although spiral welded pipes and straight-seam welded pipes are at the same level, spiral welded pipes possess higher impact toughness. Due to changes in pipeline flow rates, in practical operation, steel pipes are subjected to random alternating loads. Steel pipes with low cyclic fatigue strength are of great significance for determining the service life of pipelines. The measurement results show that spiral welded pipes have the same fatigue strength as seamless pipes and resistance-welded pipes, which are from the same region; however, their fatigue strength is higher than that of longitudinally welded pipes. •On-site weldability: On-site weldability mainly depends on the material of the steel pipe and the dimensional tolerances of its ends. Given the requirements of pipeline installation, steel processing, as well as consistency in continuity and geometry, are of particular importance. The production of spiral welded pipes involves basically the same working conditions and a stable, continuous process: the longitudinal production sequence is segmented, comprising the entire process of plate/head/forward rolling/stocking/welding/finishing/assembly. This is an important feature that distinguishes the production of spiral welded pipes from that of other types of welded pipes. Stable production conditions make it easy to ensure welding quality control and geometry. In spiral welded pipes, the welds are evenly distributed at regular intervals, unlike in straight-seam welded pipes. The nozzles of spiral pipes are aligned vertically with the pipe surface, which helps to ensure high precision in the welding process. •The influence of the flow properties of the transmission medium: the pressure drop and pipe length in the conveying pipeline are proportional to the fluid viscosity coefficient, flow velocity, and fluid resistance coefficient, while the pipe diameter is inversely proportional to these values. The Reynolds number fluid resistance coefficient is related to the roughness of the inner wall surface of the pipe. It has been determined that the surface roughness of the inner wall of the pipe is 10 times greater than that of the local protrusions in that area, such as spiral welds or longitudinal welds, or even the inner circumferential welds. •Production and management: The spiral welded steel pipes produced offer higher quality and efficiency advantages. The production capacity of a spiral welded pipe manufacturing line is equivalent to that of 5–8 vertical processing units. Ensuring that multiple such production lines can meet the same quality standards requires adhering to a unified manufacturing process and quality assurance system in order to achieve the necessary level of quality in pipe fabrication, which is a challenging task. The amount of long-term production capacity exceeds the growth rate in project management and quality supervision. Multiple straight-seam volume control units and the corresponding welding equipment, along with operational skills, quality awareness, as well as differences in distribution points and control procedures, can lead to many difficulties in management and production scheduling, inspection and acceptance, delivery, and coordination. This creates challenges in coordinating quality control among busy manufacturers and construction firms. •Quality assurance: In accordance with the standards for the production of spiral welded pipes, the inspection/control items for such pipes include: dimensions – outer diameter, wall thickness, ellipticity, curvature, and the condition of the ends of the pipe; length; appearance quality – misalignment on the pipe surface, delamination, inclusions, and weld defects. Chemical composition analysis, tensile tests on the welded joints, hydrostatic testing, etching tests, and non-destructive testing are also carried out. There are no standard specifications for longitudinal aspects of these pipes. Under normal circumstances, continuous inspection is carried out on the spiral welded pipe rolling line to ensure the quality of the welding; this is another important feature of spiral welded pipe production, which sets it apart from other types of pipe production. Continuous inspection facilitates the detection of weld defects, ensures stable welding quality, and guarantees the welding grade. Due to limitations in the production process, it is extremely difficult to carry out continuous inspection of straight-seam welded pipes. This will increase the risks associated with welding quality issues, and may even affect the overall reliability of pipeline operation. •Production qualification: Spiral welded pipe manufacturers must hold an industrial product production license issued by **. The licensing system requires that manufacturers of spiral welded pipes must first have the necessary production facilities; their equipment must be subject to authoritative inspection by **evaluated and recognized certification bodies, and they must have a sound and effective quality assurance system. The products must meet the standards and quality requirements set forth in relevant regulations, as well as undergo certification by the National Office for Industrial Product Production Licenses. Spiral welded pipe manufacturers have a quality assurance system and quality control procedures. Requirements for industrial product production licenses of vertical manufacturers. •Price analysis: The performance of higher-grade hot-rolled coil materials, as well as the production processes involved, mean that, on one hand, there are fewer domestic manufacturers that meet the relevant standards compared to those producing steel plates. On the other hand, due to their production processes and quality levels, the market price of such materials is higher than that of hot- and cold-rolled steel plates. The main reason for the market price of spiral welded pipes is that, compared to the factors that determine the selling price of steel pipes, the cost of the material plays a dominant, even decisive, role. By checking, the price of spiral welded pipes is slightly higher than that of longitudinal spiral welded pipes; this price difference is due to variations in the cost of the main materials used in production. Spiral welded pipe production is part of steel pipe manufacturing; however, considering factors such as the overall quality of the project and its cost, it still holds overall advantages. Materials with metallurgical properties for the production of straight-seam submerged-arc welded steel, as well as for the production of spiral welded pipes and hot-rolled coils. Through advantages such as hot continuous rolling, high-quality steel is produced, leveraging advanced metallurgical processing capabilities. For example, a water cooling system is installed on the output station to accelerate cooling, allowing the use of low-alloy components in order to achieve a specific strength level and low-temperature toughness, thereby improving the weldability of the steel. But a basic steel production plant. The alloy content (carbon equivalent) of the coil is usually lower than that of steel plates of similar grades, which also improves the weldability of the spiral welded pipe. It should be noted that, since the rolling direction of the coil in spiral welded pipes is not perpendicular to the pipe axis (depending on the solution for the fold at the helix angle), whereas the rolling direction of the steel plates in straight-seam pipes is perpendicular to the pipe axis, the crack resistance of spiral welded pipe materials is superior to that of straight-seam pipes. •Welding processes involve the methods used to weld spiral welded pipes and straight-seam steel pipes; however, longitudinal welding often results in numerous T-joints, which increases the likelihood of welding defects. Moreover, due to the residual stresses associated with T-joint welding, the welded metal is typically in a three-dimensional stress state, thereby increasing the risk of cracks. According to the requirements of each welding process in submerged arc welding, the arc should be extinguished at each longitudinal weld seam; if this condition cannot be met, it may result in welding defects. •Strength properties refer to the internal pressure that a pipe can withstand, typically the two principal stresses on the wall: the radial stress ΔY and the axial stress δX. The stress generated by welding is δ=ΔY(1/4sin2α+cos2α)1/2, where α is the helix angle of the spiral welded pipe. The helix angle of spiral welded pipes is generally 50–75 degrees; therefore, the stress generated in the spiral weld accounts for 60–85% of the longitudinal principal stress. Under the same working pressure, the wall thickness of straight-seam welded steel pipes made from spiral welded pipes of the same diameter can be reduced. Based on these characteristics, it is said that: the pressure exerted on spiral welded pipes during explosion welding is relatively low, and the rupture point generally does not originate from the spiral weld, resulting in good longitudinal safety. B. For defects that are parallel to and located near the spiral weld, the stress on the spiral weld is lower; therefore, the risk of expansion is not as great as that in the case of straight welds. C. Since radial stress is the maximum stress in the pipe, the normal stress in this direction is highest at the weld under maximum load. It bears the loads applied to the circumferential weld seam, as well as the loads between the spirals. •The hydraulic bursting strength was verified through comparative tests, showing that the measured bursting pressure of spiral welded pipes at their longitudinal yield pressure is within a small deviation from the theoretical value. However, both the yield pressure and the burst pressure are lower for spiral welded pipes compared to straight-seam welded pipes. Blasting tests also showed that the circumferential deformation rate at the blast site of spiral welded pipes is significantly higher than that in the longitudinal direction; the plastic deformation at the blast site of such pipes is generally confined to one pitch, with the expansion of the spiral weld being limited by strong constraints. •Toughness and fatigue strength: The development trend for these pipelines is larger diameters and higher strength. As the pipe diameter increases and the steel grade rises, there is a tendency for the tip of the ductile fracture to expand steadily, thereby increasing in size. According to tests conducted by relevant American research institutions, although spiral welded pipes and straight-seam welded pipes are at the same level, spiral welded pipes possess higher impact toughness. Due to changes in pipeline flow rates, in practical operation, steel pipes are subjected to random alternating loads. Steel pipes with low cyclic fatigue strength are of great significance for determining the service life of pipelines. The measurement results show that spiral welded pipes have the same fatigue strength as seamless pipes and resistance-welded pipes, which are from the same region; however, their fatigue strength is higher than that of longitudinally welded pipes. •On-site weldability: On-site weldability mainly depends on the material of the steel pipe and the dimensional tolerances of its ends. Given the requirements of pipeline installation, steel processing, as well as consistency in continuity and geometry, are of particular importance. The production of spiral welded pipes involves basically the same working conditions and a stable, continuous process: the longitudinal production sequence is segmented, comprising the entire process of plate/head/forward rolling/stocking/welding/finishing/assembly. This is an important feature that distinguishes the production of spiral welded pipes from that of other types of welded pipes. Stable production conditions make it easy to ensure welding quality control and geometry. In spiral welded pipes, the welds are evenly distributed at regular intervals, unlike in straight-seam welded pipes. The nozzles of spiral pipes are aligned vertically with the pipe surface, which helps to ensure high precision in the welding process. •The influence of the flow properties of the transmission medium: the pressure drop and pipe length in the conveying pipeline are proportional to the fluid viscosity coefficient, flow velocity, and fluid resistance coefficient, while the pipe diameter is inversely proportional to these values. The Reynolds number fluid resistance coefficient is related to the roughness of the inner wall surface of the pipe. It has been determined that the surface roughness of the inner wall of the pipe is 10 times greater than that of the local protrusions in that area, such as spiral welds or longitudinal welds, or even the inner circumferential welds. •Production and management: The spiral welded steel pipes produced offer higher quality and efficiency advantages. The production capacity of a spiral welded pipe manufacturing line is equivalent to that of 5–8 vertical processing units. Ensuring that multiple such production lines can meet the same quality standards requires adhering to a unified manufacturing process and quality assurance system in order to achieve the necessary level of quality in pipe fabrication, which is a challenging task. The amount of long-term production capacity exceeds the growth rate in project management and quality supervision. Multiple straight-seam volume control units and the corresponding welding equipment, along with operational skills, quality awareness, as well as differences in distribution points and control procedures, can lead to many difficulties in management and production scheduling, inspection and acceptance, delivery, and coordination. This creates challenges in coordinating quality control among busy manufacturers and construction firms. •Quality assurance: In accordance with the standards for the production of spiral welded pipes, the inspection/control items for such pipes include: dimensions – outer diameter, wall thickness, ellipticity, curvature, and the condition of the ends of the pipe; length; appearance quality – misalignment on the pipe surface, delamination, inclusions, and weld defects. Chemical composition analysis, tensile tests on the welded joints, hydrostatic testing, etching tests, and non-destructive testing are also carried out. There are no standard specifications for longitudinal aspects of these pipes. Under normal circumstances, continuous inspection is carried out on the spiral welded pipe rolling line to ensure the quality of the welding; this is another important feature of spiral welded pipe production, which sets it apart from other types of pipe production. Continuous inspection facilitates the detection of weld defects, ensures stable welding quality, and guarantees the welding grade. Due to limitations in the production process, it is extremely difficult to carry out continuous inspection of straight-seam welded pipes. This will increase the risks associated with welding quality issues, and may even affect the overall reliability of pipeline operation. •Production qualification: Spiral welded pipe manufacturers must hold an industrial product production license issued by **. The licensing system requires that manufacturers of spiral welded pipes must first have the necessary production facilities; their equipment must be subject to authoritative inspection by **evaluated and recognized certification bodies, and they must have a sound and effective quality assurance system. The products must meet the standards and quality requirements set forth in relevant regulations, as well as undergo certification by the National Office for Industrial Product Production Licenses. Spiral welded pipe manufacturers have a quality assurance system and quality control procedures. Provisions for manufacturers under industrial production licenses on a vertical basis. •Price analysis: The performance of higher-grade hot-rolled coil materials, as well as the production processes involved, mean that, on one hand, there are fewer domestic manufacturers that meet the relevant standards compared to those producing steel plates. On the other hand, due to their production processes and quality levels, the market price of such materials is higher than that of hot- and cold-rolled steel plates. The main reason for the market price of spiral welded pipes is that, compared to the factors that determine the selling price of steel pipes, the cost of the material plays a dominant, even decisive, role.