In the field of oil and gas transportation, LSAW Steel Pipes and SSAW Steel Pipes are widely used, each with its own characteristics. Which one is better depends on the specific working conditions and requirements.

1. LSAW steel pipes are used for better oil and gas transportation

In terms of dimensional accuracy

LSAW steel pipes (especially UOE forming processes) undergo precise mold pressing and forming processes during the manufacturing process. For example, the forming steps of U-shape and O-shape enable the roundness of steel pipes to reach a high standard, and the diameter deviation can be controlled within a very small range, generally reaching a diameter tolerance range of ± 0.75% ± 1.0%. Accurate pipe diameter is crucial for maintaining stable oil and gas flow in high-pressure oil and gas transportation. According to the principles of fluid mechanics, small changes in pipe diameter can lead to significant changes in flow velocity and pressure loss. Taking long-distance natural gas transmission pipelines as an example, if the diameter deviation is too large, it will cause uneven flow velocity of natural gas in the pipeline, increase local pressure drop, and thus affect the efficiency of the entire transmission system.

Moreover, the wall thickness accuracy of LSAW steel pipes is also very high, which can ensure uniform stress distribution on the pipe wall when subjected to high pressure. In the design of oil and gas transmission pipelines, the wall thickness is calculated based on factors such as the maximum pressure the pipeline can withstand and the yield strength of the pipe material. Accurate wall thickness control can ensure safe operation of pipelines under design pressure. For example, in high-pressure crude oil pipelines, uneven wall thickness may cause local areas to bear excessive stress, leading to pipeline failure, while the high-precision wall thickness of LSAW steel pipes can effectively avoid this situation.

In terms of mechanical properties

The welding process of LSAW steel pipes (such as double wire or multi wire submerged arc welding) can ensure high quality of welds. The toughness and plasticity of the weld can be well integrated with the base metal, making the steel pipe have good mechanical properties as a whole. In long-distance and high-pressure oil and gas transportation environments, pipelines must withstand the pressure of internal oil and gas as well as various external forces. For example, when pipelines pass through mountainous areas, they are subject to lateral pressure from the mountain and impact forces from geological disasters such as earthquakes. The high toughness of LSAW steel pipes enables them to absorb energy through their own deformation when subjected to external forces, rather than directly breaking.

From the perspective of material mechanics, the axial and circumferential strength of LSAW steel pipes can meet strict requirements for oil and gas transportation. Its axial strength can withstand the tensile stress of the pipeline during the laying process, especially when using elastic laying or crossing rivers, valleys and other special laying methods. The axial strength of the pipeline ensures that it will not deform or be damaged due to tension. The circumferential strength can effectively resist the pressure of internal oil and gas, preventing pipeline swelling or rupture. For example, for deep-sea oil and gas pipelines, the high circumferential strength of LSAW steel pipes can withstand the enormous water pressure and internal pressure of oil and gas in the deep sea.

In terms of corrosion resistance

LSAW steel pipes can adopt various advanced anti-corrosion technologies. Among them, three-layer PE coating is a commonly used anti-corrosion method. The first layer is epoxy powder primer, which can tightly adhere to the surface of the steel pipe, providing a good bonding foundation for subsequent coatings; The second layer is the intermediate adhesive layer, which can firmly bond the outer layer of polyethylene with the inner layer of epoxy powder; The third layer is the polyethylene outer protective layer, which can effectively isolate the steel pipe from corrosive media outside. This coating combination can resist various acidic and alkaline components in soil, salt in seawater, and corrosive gases in the atmosphere.

In some coastal oil and gas pipelines, salt spray and tidal changes in seawater can cause severe corrosion to steel pipes. The three-layer PE coating on LSAW steel pipes can provide long-term protection and extend the service life of the pipeline. Moreover, in areas with high groundwater levels and strong soil corrosiveness, such as swamps or saline alkali land, this anti-corrosion coating can also effectively protect steel pipes. According to actual testing, LSAW steel pipes coated with three layers of PE can have a service life several times longer than uncoated steel pipes in these harsh environments.

Applicability of high-grade pipelines

For oil and gas pipelines with high conveying pressure and large conveying capacity requirements, high-grade pipe materials are often required. LSAW steel pipes can meet the requirements of high-grade pipes such as X70 and X80 in API 5L standards. These high-grade pipes have higher yield strength and tensile strength, which can improve the efficiency of oil and gas transportation while ensuring safety.

Taking X80 grade LSAW steel pipe as an example, its minimum yield strength can reach 555MPa, which enables it to withstand higher pressure under the same pipe diameter and wall thickness conditions. When constructing large-scale cross-border oil and gas trunk pipelines, using high-grade LSAW steel pipes such as X80 can reduce pipeline wall thickness, thereby reducing pipe costs and construction difficulties. Meanwhile, due to its high strength, it can also increase the conveying pressure of pipelines and improve the transportation volume of oil and gas.

2. SSAW steel pipes are used for better oil and gas transportation

Adaptability aspect

SSAW steel pipe is spiral seam welded, and its shape and size can be flexibly changed by adjusting the width and helix angle of the strip steel. In the construction of oil and gas pipelines, it is often necessary to bypass obstacles such as mountains, rivers, buildings, etc. SSAW steel pipes can flexibly change the direction of the pipeline according to the actual terrain and the distribution of obstacles. For example, in the laying of oil and gas distribution pipelines around cities, it is necessary to bypass various underground facilities and building foundations. The flexibility of SSAW steel pipes can reduce the number of pipe fittings (such as elbows, bends, etc.) used, lower construction costs and difficulties.

Moreover, the spiral structure of SSAW steel pipes gives them better flexibility to a certain extent. In areas with frequent seismic activity or unstable geological conditions, this flexibility can enable pipelines to better adapt to small ground displacements and deformations, reducing the risk of pipeline rupture caused by geological activity. From the perspective of pipeline laying, the adaptability of SSAW steel pipes can improve the efficiency of pipeline laying, especially in complex terrain conditions, enabling faster completion of pipeline laying work.

Advantages of continuous spiral welding seam

The spiral weld of SSAW steel pipe has unique advantages in withstanding circumferential stress. In the process of oil and gas transportation, the circumferential stress generated by the internal pressure of the pipeline is mainly shared by the weld seam and the pipe wall. The spiral weld seam of SSAW steel pipe can make the stress distribution more uniform. From the perspective of mechanical principles, there is a certain angle between the direction of the spiral weld and the direction of the circumferential stress, which makes the transmission of stress between the weld and the pipe wall smoother. Relatively speaking, it may perform better in resisting pipeline deformation caused by circumferential stress.

Taking pipelines transporting high-pressure natural gas as an example, when the internal pressure of the pipeline is high, circumferential stress will cause the pipeline to have a tendency to expand outward. The spiral weld of SSAW steel pipe can effectively disperse this stress, avoid stress concentration at a certain point or area, and thus improve the deformation resistance of the pipeline. Moreover, during the long-term operation of pipelines, this uniform stress distribution helps to extend the service life of pipelines and reduce problems such as weld cracking or pipe wall damage caused by excessive local stress.

Economically speaking

The production cost of SSAW steel pipes is relatively low. Its production process is relatively simple, mainly welding the coiled steel strip after coiling, and the equipment investment is also relatively small. Compared with LSAW steel pipes, SSAW steel pipes do not require complex forming molds (such as UOE forming large molds) and high-precision processing equipment in the production process. This makes SSAW steel pipes more competitive in some cost sensitive oil and gas transportation projects.

For oil and gas pipelines with low transmission pressure and short distance, such as oil and gas distribution pipelines within or around cities, choosing SSAW steel pipes can effectively reduce pipe procurement costs while ensuring basic performance. For example, in the construction of a natural gas distribution network in a medium-sized city, the use of SSAW steel pipes can save a lot of pipe procurement costs while meeting the requirements for safe transportation of natural gas. These costs can be used for the construction of other supporting facilities for the pipeline (such as valves, pressure regulating stations, etc.), improving the cost-effectiveness of the entire transportation system.

If it is a high-pressure, large-diameter, long-distance oil and gas transportation project with extremely high requirements for pipeline size accuracy and mechanical performance, such as cross-border oil and gas trunk transportation, LSAW steel pipes may be a better choice; For some oil and gas transmission pipelines with moderate pressure, complex routes, and high cost control requirements, such as oil and gas distribution pipelines around cities, SSAW steel pipes have more advantages.