1. Strength requirements

Enduring high pressure: In long-distance transportation of oil and natural gas, pipelines need to withstand high internal pressure. SSAW Steel Pipes must have sufficient strength to withstand these pressures to prevent pipeline rupture. Generally speaking, the pressure of pipelines transporting natural gas may be around 10-20 MPa, while the pressure of pipelines transporting oil may also vary depending on factors such as transportation volume and viscosity. Therefore, the yield strength of steel pipes usually needs to meet high standards, such as X60 X80 grade steel (yield strength of 414MPa and 552MPa respectively), which is often used in high-pressure transmission pipelines to ensure the safety of pipelines in long-term high-pressure environments.

Resistance to external pressure: In addition to internal pressure, pipelines also need to resist external pressure, such as soil pressure on buried pipelines. Especially when passing through complex terrains such as mountainous areas and rivers, the situation of external pressure is even more complex. The wall thickness and material selection of SSAW steel pipes need to consider these factors to ensure that the pipes will not deform or be damaged under external pressure.

2. Corrosion resistance requirements

Resistance to medium corrosion: Petroleum and natural gas contain various corrosive components. The components such as water and hydrogen sulfide in natural gas, as well as acidic substances and sulfides in petroleum, can all cause corrosion to pipelines. For SSAW steel pipes, good corrosion resistance is required to resist the erosion of these media. Anti corrosion coatings such as epoxy powder coating and three-layer PE coating (polyethylene coating) are usually used to enhance the corrosion resistance of steel pipes. These coatings can form a protective film on the surface of the steel pipe, preventing corrosive substances from coming into contact with the steel pipe substrate, thereby extending the service life of the pipeline.

Dealing with soil corrosion: For buried pipelines, factors such as soil acidity, humidity, and salt content can all have a corrosive effect on the pipeline. The corrosiveness of soil varies greatly in different geographical regions. Therefore, SSAW steel pipes need to adapt to various soil environments. For example, in highly corrosive soil areas such as saline alkali land, thicker anti-corrosion coatings or a combination of cathodic protection measures and anti-corrosion coatings may be required to prevent pipelines from being corroded by soil.

3. Dimensional accuracy and quality requirements

Accuracy of pipe diameter and wall thickness: Long distance transportation pipelines require high accuracy in pipe diameter and wall thickness. Accurate pipe diameter can ensure the efficiency of pipeline transportation and the sealing of connections. Generally speaking, the tolerance range of pipe diameter should be controlled within a small range. For example, for large-diameter pipelines, the pipe diameter tolerance may be required to be within ± 1%. The wall thickness also needs to be uniform to ensure that the strength of each part of the pipeline is uniform and prevent local weak points caused by uneven wall thickness.

Weld quality: SSAW steel pipes are manufactured through spiral submerged arc welding process, and weld quality is crucial. The weld seam needs to have strength and corrosion resistance equivalent to the steel pipe substrate. During the welding process, welding parameters such as welding current, voltage, welding speed, etc. must be strictly controlled to ensure the quality of the weld seam. At the same time, non-destructive testing should be carried out on the weld seam, such as ultrasonic testing, X-ray testing, etc., to ensure that there are no defects such as porosity, slag inclusion, and lack of fusion inside the weld seam.

4. Resilience requirements

Fracture resistance: During long-distance transportation, pipelines may face various complex stress conditions, such as geological activity, temperature changes, third-party damage, etc. SSAW steel pipes need to have good toughness to resist the risk of fracture caused by these factors. Steel pipes with good toughness can absorb energy through their own deformation when subjected to external impact or stress concentration, rather than directly breaking. For example, in cold regions, pipelines need to be able to withstand the impact of low-temperature environments without brittle fracture, which requires steel pipes to have good low-temperature toughness.

Adapting to changes in geological conditions: Oil and gas pipelines may cross different geological regions, such as areas with frequent seismic activity and permafrost zones. In these areas, steel pipes need to be able to adapt to changes in geological conditions. SSAW steel pipes with high toughness can resist deformation and damage caused by geological disasters such as earthquakes to a certain extent, ensuring the integrity and safety of pipeline transportation.

5. Connection performance requirements

Good welding performance: The long-distance laying of pipelines requires connecting multiple sections of steel pipes, so the steel pipes need to have good welding performance. This includes being easy to weld, ensuring welding quality, and ensuring that the strength and corrosion resistance of the welded joint are equivalent to those of the steel pipe body. During the welding process, the material of the steel pipe should match the welding material to ensure stable quality of the welded joint.

Reliable connection and sealing: In addition to welding connections, pipelines may also use flange connections, mechanical connections, and other methods. Regardless of the connection method used, it is necessary to ensure the sealing of the connection to prevent oil and gas leaks. For flange connections, the selection and installation of sealing gaskets should meet the requirements; For mechanical connections, the design and manufacturing of sealing structures should be able to withstand the pressure inside the pipeline and ensure long-term sealing effectiveness.

6. Temperature resistance performance requirements

Adapt to changes in medium temperature: The temperature of oil and natural gas varies depending on factors such as origin and transportation conditions. Natural gas may experience an increase in temperature after compression and other treatments, while oil is extracted at different temperatures in different reservoir environments. SSAW steel pipes need to be able to withstand the temperature range of the medium. For example, in some high-temperature oil reservoirs where the oil extracted has a high temperature, steel pipes should be able to withstand this high temperature to prevent material performance degradation. At the same time, for natural gas transportation at low temperatures, steel pipes should also avoid problems such as embrittlement in low-temperature environments.

Resistance to environmental temperature changes: The range of environmental temperature changes for pipeline laying is also very wide, especially in areas with large temperature differences between day and night or seasons. Steel pipes need to be able to adapt to temperature changes in this environment without generating excessive thermal stress. Thermal stress may cause problems such as pipeline deformation and weld cracking, so the material and structure of steel pipes should have good thermal stress resistance to ensure the stability of pipelines in different temperature environments.

7. Requirements for fatigue resistance performance

Dealing with pressure fluctuations: During the transportation of oil and gas, the pressure inside pipelines can fluctuate due to various factors. For example, the start stop of the compressor and changes in the user's usage can cause pressure fluctuations. SSAW steel pipes need to have good fatigue resistance and be able to withstand frequent pressure fluctuations without experiencing fatigue cracks. The generation and propagation of fatigue cracks may lead to the ultimate rupture of pipelines, causing serious leakage accidents.

Resistance to fluid impact: When fluid flows inside a pipeline, it will have an impact on the pipe wall, especially at bends, tees, and other parts of the pipeline. Long term fluid impact may cause local fatigue damage to steel pipes. Therefore, the design and material selection of steel pipes should consider their ability to resist fluid impact, and improve their fatigue resistance through reasonable pipeline layout and thickening of key pipe walls.

8. Traceability and Quality Assurance Requirements

Material traceability: For SSAW steel pipes used in long-distance transportation pipelines, a comprehensive material traceability system is required. From the procurement of raw materials, production and processing processes to the delivery of final products, the relevant information of each steel pipe should be traceable. This includes information such as furnace batch number, chemical composition, production time, and production process parameters of the steel, in order to quickly identify the cause and take corresponding measures when problems occur.

Quality certification and standard compliance: Steel pipes must comply with strict industry standards and quality certification systems, such as API (American Petroleum Institute) standards. These standards cover multiple aspects such as the material, manufacturing process, dimensional accuracy, and performance testing of steel pipes. Manufacturers need to undergo strict quality testing and third-party certification to ensure that the quality of SSAW steel pipes meets the requirements for long-distance transportation of oil and natural gas. At the same time, quality assurance documents should be delivered together with the product to provide quality basis for pipeline construction and operation.