How Understanding API Line Pipe Can Save You Money on Your Steel Piping Project

What is API 5L Line Pipe?

In this article you’ll learn about API 5L Line pipes. The specification of the API 5L covers seamless and welded pipes for transporting oil, gas, water in the oil & gas and petrochemical industries.

API introduced by the American Petroleum Institute (API) API-5L standard early in 1926, initially featuring three grades of steel A25, A, B, and updated several times later. API 5L welded steel pipe is used primarily for the supply of onshore and offshore oil and gas, coal slurry, slurry media and offshore platforms, power plants, chemical and urban construction, structural tubes.

API 5L Carbon Steel Pipes specifications adhere to ISO 3183, the International Organization for Standardization, which standardizes pipeline transportation systems for the petroleum, petrochemical and natural gas industries in the materials, equipment and offshore structures. The technical committee authoring the standards recognized that there are two basic Product Specifications Levels (PSL) of technical requirements and therefore developed PSL 1 and PSL 2.  PSL 1 is a standard quality for line pipe where PSL 2 contains additional chemical, mechanical properties, and testing requirements.

Grades covered by this specification are A25, A, B (and the following “X” Grades), X42, X46, X52, X56, X60, X65, X70, X80.  The two-digit number following the “X” indicates the Minimum Yield Strength (in 000’s psi) of pipe produced to this grade.

API 5L Line Pipe production is currently using a micro-alloy heating treatment process. The production costs of seamless stainless steel pipe are significantly higher than the welding pipe and with the increase of steel grade, the limit of carbon content is more and more strict. At present, all the major manufacturers carry out research work in order to improve the corrosion resistance of the pipeline and ensure stable performance at low and high temperatures.

API 5L pipes may be classified according to the following criteria:

execution: seamless or welded (seamless pipes may be used up to 24 inches, LSAW above 24 inches, ERW up to 20 inches)

Specification level (API PSL1, PSL2): PSL1 is a standard quality used for pipelines, whereas PSL2 sets more stringent chemical, mechanical properties, and testing requirements

Surface finish: black, varnish painted, anti-rust oil, galvanized, coated externally (3PL) and/or lined internally

ends types: plain, beveled, threaded ends

The main advantages of API 5L pipe are:

Resistance to cracking forces that may propagate in long pipelines

Sour service suitability

Rather inexpensive and long service life (at least grades B, X42)

Size Range

API 5L pipes are available in dimensions between from 2 to 28″ (seamless execution) and up to 80″ in welded execution (generally, LSAW i.e. longitudinal submerged arc welding).

The API 5L and ASME B36.10 pipe dimensions and weights are, in fact, identical.