API 5L Line Pipe Guide: PSL1 vs PSL2, Grades and Sizing
API 5L is the international specification for line pipe used in oil and gas transmission systems. If you are buying seamless line pipe for a pipeline project, this guide helps you specify the right product.
PSL1 vs PSL2
API 5L defines two product specification levels:
- PSL1 — the base quality level. Chemical composition and mechanical properties are guaranteed with normal tolerances. Suitable for less demanding service.
- PSL2 — stricter requirements. Tighter chemistry control, mandatory impact (Charpy) tests in most cases, and individual certification of every pipe. Required for many cross-country gas pipelines and sour service.
In general, PSL2 commands a higher price but provides better fracture toughness and traceability. When in doubt for long-distance or high-pressure gas lines, specify PSL2.
Grade Selection
API 5L seamless line pipe is commonly supplied in these grades:
| Grade | Minimum Yield (MPa) | Typical Use |
|---|---|---|
| Gr.B | 245 | Water and low-pressure oil service |
| X42 | 290 | General oil and gas service |
| X52 | 360 | Medium-pressure pipelines |
| X60 | 415 | High-pressure transmission |
| X65 | 450 | Long-distance gas pipelines |
| X70 | 485 | Large-diameter high-pressure lines |
Higher grades use more alloy and cost more, so select the minimum grade that safely meets your operating pressure.
Size and Wall Thickness
Seamless API 5L pipe is available in nominal sizes from about 1/2“ up to 26“ (21.3 mm to 660 mm OD) with wall thicknesses from about 3 mm to 40 mm. Wall thickness is driven by the design pressure — thicker walls for higher pressure and larger diameters.
Two sizing conventions are used:
- Nominal pipe size (NPS) — inch-based designation (e.g. NPS 8)
- Actual dimensions — exact OD and wall thickness in mm or inches
Always specify the actual OD and wall thickness in your inquiry to avoid ambiguity.
Sour Service
For media containing hydrogen sulfide (H2S), specify NACE MR0175 / ISO 15156 requirements. This restricts hardness and requires additional testing. Let your supplier know early, because sour-service material is produced differently.
What to Include in Your Order
A complete line pipe order should state:
- Specification: API 5L, PSL1 or PSL2
- Grade (e.g. X52) and supplementary requirements if any
- Outer diameter, wall thickness and length (random or fixed)
- End preparation: plain end, beveled, threaded
- Coating requirements if applicable
- Quantity in meters or metric tons
Need Help Specifying?
Our engineers supply API 5L seamless line pipe from Gr.B to X70 for projects across Southeast Asia, Africa and the Middle East. Send us your design pressure and environment, and we will confirm grade, wall thickness and pricing within 24 hours.
