The history and development background of the API 5L standard are as follows:

Early stage

In 1926, the American Petroleum Institute (API) released the API 5L standard. The initial version only included three steel grades: A25, A, and B, with corresponding minimum yield strengths of 172MPa, 207MPa, and 241MPa, respectively. At that time, the oil and gas industry was in its initial development stage, and the demand for pipelines was gradually increasing. The emergence of this standard was mainly to standardize the basic quality and performance requirements of steel pipes for oil and gas transportation and ensure the safety and reliability of pipelines.

In 1947, API released the API 5LX standard, adding three new steel grades: X42, X46, and X52, with minimum yield strengths of 289MPa, 317MPa, and 358MPa, respectively. With the expansion of the scale of oil and gas extraction and transportation, the strength requirements for steel pipes have continued to increase, and the emergence of new steel grades has met this demand.

Development stage

Since 1966: Four grades of pipeline pipes, X56, X60, X65 and X70, have been launched one after another, with corresponding minimum yield strengths of 386MPa, 413MPa, 448MPa and 482MPa respectively. During this period, the technology of the oil and gas industry continued to advance, and more and more long-distance and large-diameter transmission pipelines were built. Higher-strength steel pipes can adapt to more complex working conditions and environmental conditions.

1972: API released the U80 and U100 standards, with minimum yield strengths of 551MPa and 691MPa respectively. Later, these two grades were renamed X80 and X100. This marks that the strength and performance of steel pipe materials have been further improved to meet the needs of oil and gas transportation in special environments such as deep sea and high cold.

Maturity and internationalization stage

2007: ISO and API jointly released the pipeline steel pipe standard ISO 3183:2007/API Spec 5L (44th edition), achieving a certain degree of consistency in global standards. With the development of economic globalization, international cooperation in the oil and gas industry is becoming increasingly frequent. Unified standards are conducive to reducing trade costs and improving product quality and interchangeability.

End of 2012 - 2013: API 5L 45th edition was approved and officially released on the ISO network on February 18, 2013. Compared with the previous version, the European onshore natural gas pipeline PSL2 steel pipe ordering (Appendix M) and thread and coupling calculation formulas and guide bending and Charpy impact calculation formula background (Appendix P) were added. At the same time, technical changes were made to the reference standards, manufacturing processes, performance indicators, inspection methods, etc. to make it more complete and scientific.

The differences between API 5L standard and other common standards are as follows:

Differences from GB/T 9711

Content arrangement: API 5L adds chapters such as "Consistency", "Symbols and Abbreviations", "Record Preservation", and "Steel Pipe Shipping". GB/T 9711 has "Purchaser Ordering Instructions", "Requirements", "Steel Pipe Marking" and other contents, and the two are also quite different in the appendix.

Scope of application: API 5L specifies the manufacturing requirements for seamless steel pipes and welded steel pipes of two product standard grades (PSL1 and PSL2) for pipeline transportation systems in the petroleum and natural gas industry, but does not clearly specify the material, transportation medium or specific conditions of use of the steel pipe. GB/T 9711 has more specific provisions for different parts. GB/T 9711.1 specifies the basic quality and test requirements for Grade A steel pipes, which are suitable for conveying flammable and non-flammable fluids; GB/T 9711.2 is suitable for pipes for conveying flammable fluids, and the quality and test requirements are generally higher than GB/T 9711.1; GB/T 9711.3 is suitable for steel pipes for conveying flammable fluids under special harsh conditions.

Quality grade classification: API 5L is divided into PSL1 and PSL2. PSL2 has additional mandatory requirements for chemical composition, notch toughness and strength properties. GB/T 9711 is divided into Grade A, Grade B and Grade C steel pipes, corresponding to basic quality requirements, higher than basic requirements, and strict requirements for special purposes, respectively.

Difference from ASTM standards

Scope of application: API 5L is mainly for pipeline pipes used in pipeline transportation systems in the oil and gas industry, covering seamless and welded steel pipes for transporting oil, gas, water and other media. ASTM standards cover a wide range of industries and applications, such as ASTM A53 for general-purpose pipelines, ASTM A106 for seamless carbon steel pipes for high-temperature services, and ASTM A333 for seamless and welded steel pipes for low-temperature services.

Grade classification: API 5L divides steel pipes into two product standard grades, PSL1 and PSL2, with multiple strength grades such as A25, A, B, X42 - X80. Different ASTM standards have their own grade classification systems, such as ASTM A53 has grades A and B, and ASTM A106 has grades A, B, and C.

Material focus: API 5L focuses on the performance of pipeline pipes in the oil and gas transportation environment, and has high requirements for material corrosion resistance, hydrogen embrittlement resistance and other properties. Due to the diverse application scenarios, the ASTM standard has different performance requirements for materials according to specific uses. For example, the high temperature standard focuses on the high temperature strength and stability of the material, while the low temperature standard focuses on the low temperature toughness of the material.

Differences from ISO 3183

Essential relationship: ISO 3183:2024 is basically the same as API SPEC 5L 44, and has been merged into one publication, but there are slight differences between the two in Appendix N of API SPEC 5L 44.

Historical version relationship: ISO 3183 1st edition divides the conveying steel pipe into three levels of A, B, and C and divides them into three parts, while API 5L uses PSL1 and PSL2 and adds an appendix to integrate different steel pipes.