Dual certified materials can be used at either rating. In your case you will want to look at the welding that was used to ensure the welds are not the limiting factor.
API 5L is a materials specification and so does not list joint efficiency.
You will need to look in a design code such as ASME B31.3 or API 31.8, or a regulatory code such as DOT Part 192. The joint efficiency will depend on the type of weld so not all API 5L PSL 1 or PSL 2 pipe will have the...
