Linepipe is a type of steel pipeline used for petroleum, natural gas, oil, and water transportation. Most of the steel pipelines are used in regions with severe natural conditions, such as polar regions, ice fields, deserts and oceans, etc. The lines are long and not easy to maintain, which requested strict quality requirements and specifications. The pipeline steel consists of seamless and welded steel tubes according to its manufacturing methods and made of high strength carbon steel., which can be laid in cold, high-sulfur areas or under the sea.
This linepipe typically has good mechanical properties such as wall thickness, high strength, high toughness and wear resistance, but also should be large diameter, good weldability, low-temperature resistance, corrosion resistance (CO2), seawater resistance and HIC, SSCC performance.
Steel pipeline not only requires high tensile strength and yield strength but also provides a buckling ratio of 0.85~0.93.
High impact toughness
High impact toughness prevents cracking.
Low ductile-brittle transition temperature
Harsh regional and climatic conditions require the pipeline steel to have a sufficiently low ductile and brittle transition temperature. The shear area of DWTT (drop hammer tear test) has become the main control index to prevent the brittle failure of the pipeline, and it is generally required that the fracture shear area of the sample should be ≥85% at the lowest operating temperature.
Excellent hydrogen-induced cracking (HIC) and sulfide stress corrosion cracking (SSCC) resistance
Good welding performance
Currently, the main technical standards for oil and gas conveying steel linepipes are API SPEC 5L, DNV-OS-F101, ISO 3183 and GB/T 9711, etc.
API 5L is a widely used specification developed by the main petroleum institute, which is only for steel pipe products, excluding the design, selection or installation of pipelines.
DNV-OS-F101 (subsea pipeline system) is a specification developed by Norske veritas specifically for subsea pipelines. It covers a wide range of contents, including pipeline design, materials, manufacturing, installation, testing, operation, maintenance, etc., which is usually stricter than API 5L.
ISO 3183 is the international organization for standardization developed on the oil and gas transport steel pipe delivery conditions, the standard is comprehensive, detailed but does not involve the pipeline design, installation, etc.
Process Specification Language
Note: the number after L represents the minimum yield strength (MPa); The number after X also indicates the minimum yield strength (1000psi); Delivery condition: R= rolling, N= normalizing (normalizing + tempering), Q= quenching + tempering, M= thermo-mechanical rolling; The suffix P indicates a specified amount of phosphorus.
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