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Analysis of MARINE SEAMLESS STEEL PIPE and Its Differences from Common Steel Pipes

I. Definition and Application

MARINE SEAMLESS STEEL PIPE is a kind of seamless steel pipe specially designed for shipbuilding and Marine engineering, mainly used for the structural support of ship power systems, fuel/lubricating oil transportation, ballast water pipelines and offshore platforms. Its core feature is to adapt to harsh Marine environments such as high salinity, high humidity and high pressure.

II. Differences from Common Steel Pipes

Material and corrosion resistance
Marine steel pipes: Alloying elements such as copper (Cu), nickel (Ni), and chromium (Cr) are added to enhance the resistance to seawater corrosion. Some parts are made of duplex stainless steel or coated with technologies (such as galvanizing and epoxy resin).
• Common steel pipes: Mostly carbon steel (such as Q235), without special anti-corrosion treatment, and only used in general environments.

III. Production process

• Manufacturing standards: It is necessary to pass the certification of classification societies (such as DNV-GL, ABS, LR), and the production process must comply with the "Specification for Special Seamless Steel Pipes for Ships".
• Testing requirements: In addition to the conventional hydrostatic test, mandatory ultrasonic flaw detection (UT) and magnetic particle testing (MT) are required to ensure there are no internal defects.
• Heat treatment process: Normalizing treatment or quenching and tempering are often adopted to optimize mechanical properties.

IV. Mechanical properties

• Compressive strength: It is usually required to be ≥490 MPa (such as in the Marine GB/T5312 standard), which is higher than that of ordinary fluid pipes (such as 415 MPa in ASTM A106).
• Low-temperature toughness: It needs to pass the Charpy impact test at -40℃ to adapt to the low-temperature environment of polar shipping routes or deep sea.

V. Application Scenarios

Marine steel pipes: high-pressure fuel pipes for ship engines, subsea valve systems, and low-temperature pipelines for LNG carriers (operating at -162℃).
• Common steel pipes: Building scaffolding (GB/T13793), municipal water pipes (GB/T3091), and general mechanical structural components.

VI. Special Certifications and Cost Factors

• Certification Requirements: A classification society certificate (such as CCS China Classification Society) must be obtained, and some projects need to comply with IMO (International Maritime Organization) regulations.
• Cost difference: The price of Marine pipes is 30% to 50% higher than that of ordinary pipes of the same specification, mainly due to alloy costs, inspection fees and certification procedures.

VII. Summary

Marine seamless steel pipes far exceed ordinary steel pipes in terms of material formula, production control and testing standards, and are the cornerstone of Marine engineering safety. When making a choice, the application scenario should be clearly defined: If it is used in a non-corrosive low-pressure environment (such as indoor water supply), ordinary welded pipes are more economical. When it comes to Marine or high-pressure and high-temperature working conditions, marine-grade products must be used to avoid potential safety hazards.