PSL-1 tubing is a loose standard quality for line pipe, whereas PSL-2 tubing contains additional testing requirement, stricter chemical physicals, along with different ceiling limits of mechanical properties, and require Charpy impact testing conditions.
Furthermore, additional testing requirements under PSL-2 tubing include CVN testing, non-destructive inspection of seamless products, certification to SR15, and mandatory traceability throughout the entire production process. Most FERC, DOT, or FEMSA lines require PSL-2, meaning these types of requirements are a must when supplying pipe for pipelines that are regulated by any of these governing bodies.
Level PSL 1 tubing provides a standard quality level for line pipe. Level PSL 2 tubing has additional mandatory requirements for chemical composition, notch toughness and strength properties and additional NDE. Requirements that apply to only PSL 1 tubing or to only PSL 2 tubing are so designated. Requirements that are not designated to a specific PSL tubing designation apply to both PSL 1 tubing and PSL 2 tubing.