Sep 12, 2026Procurement Guides
API 5L Line Pipe: PSL1 vs PSL2 and What to Specify on the Order
API 5L covers seamless and welded line pipe for oil and gas transmission. PSL2 adds mandatory carbon equivalent, toughness, yield and NDT requirements over PSL1. Here is how to specify.
Quick answer: API 5L is the specification for seamless and welded steel line pipe used to transport oil and gas, and it defines two product specification levels. PSL1 is the base level. PSL2 is stricter: it adds mandatory requirements for carbon equivalent, notch toughness, maximum yield strength and tensile strength, and it requires non-destructive testing. On an order you must state the specification, the grade and the product specification level - PSL1 or PSL2.
What API 5L Covers
API 5L applies to line pipe for the oil and gas industry, covering both seamless and welded pipe. The specification also addresses pipe ends and connections, including plain ends and special end preparations such as pipe socket ends and tubes for a particular connection method.
PSL1 and PSL2 Explained
PSL stands for product specification level, and line pipe grades are divided into PSL1 and PSL2. The two levels differ not only in inspection requirements but also in chemical composition and mechanical performance requirements. PSL2 sits above PSL1 on every one of those counts.
In practice this means the two levels are not interchangeable on a purchase order. When ordering API 5L pipe, the contract must state not only the size and steel grade but also the product specification level.
Where PSL2 Is Stricter
Carbon equivalent: PSL2 places mandatory limits on carbon equivalent, which controls weldability and the behaviour of the heat-affected zone.
Notch toughness: PSL2 requires impact testing, while PSL1 does not require impact performance. For PSL2, all grades with the exception of X80 are subject to full-size impact testing at 0 degrees C on an average basis.
Strength limits: PSL2 specifies mandatory maximum yield strength and tensile strength, so the pipe cannot be supplied at the extreme top of the grade range.
Non-destructive testing: PSL2 requires NDT, where PSL1's requirements are lighter.
On an API 5L order, size and grade are not enough - the product specification level decides which chemistry, toughness and testing regime applies.
How to Specify an API 5L Order
State five things clearly. First, API 5L and the edition. Second, the steel grade. Third, PSL1 or PSL2. Fourth, the size and wall thickness, and the pipe end preparation. Fifth, the inspection and certificate package the project requires. Where a customer specification applies, quote it alongside API 5L so the mill knows which requirements govern.
FAQ
Is PSL2 always the right choice?
Not necessarily. PSL2 is the stricter level and is often required for critical lines, but if the duty only needs PSL1, specifying PSL2 adds cost and inspection burden without benefit.
Does API 5L cover welded pipe?
Yes. API 5L covers both seamless steel pipe and welded steel pipe.
Why does PSL1 not require impact testing?
PSL1 is the base specification level, so notch toughness testing is not a mandatory requirement. PSL2 adds it as a mandatory item.
Send your API 5L grade, PSL, sizes and destination port to our engineering team for a confirmed recommendation.
