The standard specification of API 5L steel pipe is mainly stipulated by the API SPEC 5L standard issued by the American Petroleum Institute (API). The latest version is the 46th edition released in 2018. The following are its details:

Scope of application

Applicable to seamless and welded steel pipes for gas, water and oil transportation in the oil and gas industry, including ordinary ports, threaded ports, socket ports and straight flow pipes (TFL) and other types, not applicable to cast pipes.

Product specification level

PSL1: Provides basic quality standards.

PSL2: Based on PSL1, there are mandatory requirements for carbon equivalent, notch toughness, maximum yield strength and tensile strength, and additional requirements such as chemical composition and hardness are added. It is suitable for more demanding application scenarios, such as sour environments and offshore services.

Steel grade and size specifications

Steel grade: covers A25, A25P, B, X42, X46, X52, X56, X60, X65, X70, L625Q (X90), L690Q (X100) and other steel grades.

Size

Outer diameter: ranges from 34mm to 762mm, and the outer diameter range is mentioned in API 5L-2020 Line Pipe 46th mod as 10.3mm to 2032mm.

Wall thickness: ranges from 3mm to 120mm.

Length: fixed length is generally 5.8 meters or 6 meters, and can also be based on SRL/DRL or specified length.

Technical requirements

Manufacturing process: specifies the manufacturing requirements for seamless steel pipes and welded steel pipes, including process control and quality assurance during the production process.

Chemical composition: Different steel grades have different chemical composition requirements, such as the content limits of carbon, manganese, phosphorus, sulfur and other elements. Taking PSL2 X52 as an example, C≤0.22%, Mn≤1.40%, P≤0.025%, S≤0.015%, Ti≤0.04, Nb+V+Ti≤0.15%, Pcm≤0.25, CEIIW ≤0.43.

Mechanical properties

Tensile properties: The specified total elongation stress Rt0.5, tensile strength Rm, elongation A and other indicators of different steel grades are specified. For example, for PSL2 X52 steel pipe, the tensile requirements of the pipe body are 531MPa≥Rt0.5≥359MPa, 758Mpa≥Rm≥455MPa, Rt0.5/Rm ≤0.93, A50.8≥26%.

Bending performance: The weld guided bending test usually requires the use of a specific bending shaft diameter and bending angle, such as a bending shaft diameter of D78.7mm and a bending angle of about 180º.

Impact performance: Charpy impact test and DWTT drop weight tear test are required, and there are clear regulations on test temperature, specimen size, impact energy, shear area, etc.

Nondestructive testing

UT inspection of steel plates: Acceptance according to API 5L PSL2 and ASTM A435.

Weld inspection: 100% UT is performed on the entire length of the weld before the hydrostatic test, and 100% UT and 100% RT are performed on the entire length of the weld after the hydrostatic test, all of which are accepted according to API 5L PLS2.

Appearance and dimensional deviation

Appearance: The inner and outer surfaces of the steel pipe should be clean, and no defects such as delamination, cracks, scars, folds, bubbles, inclusions, etc. that are harmful to use are allowed. There should be no grease, excessive rust, flux and corrosive substances, etc.

Outside diameter deviation: The difference between the average diameter of one end of the steel pipe and the average diameter of the other end is specified, such as not more than 2.4mm (difference in outer circumference ≤7.5mm).

Wall thickness deviation: There is a clear range of allowable deviation of wall thickness, and the negative deviation of the actual weight of the total delivery and the theoretical weight is required not to exceed 3%.

Ovality: Pipe end ≤6mm, pipe body ≤8mm.

Straightness: Full length straightness ≤0.2% pipe length mm, local straightness ≤2mm per 1000mm.

End requirements

The end straightness has clear requirements and standardized markings, such as pipe end groove angle 30°±5°, blunt edge 1.6±0.8mm, pipe end bevel ≤1.6mm.

Implementation and certification

From November 1, 2018, all manufactured API SPEC 5L steel pipes must comply with the requirements of the 46th edition and pass the Monogram certification.