Thanks very much LittleInch.
I know that in FK300 the code states as follows: "Although High Pressure Fluid Service is often considered to be service exceeding that allowed by the ASME B16.5, Class 2500 pressure–temperature rating for a particular material group, there are no pressure limitations for the application of these rules. The decision by an owner to specify High Pressure Fluid Service is based on the economic, technical, and other issues pertaining to the piping".
However I just wanted to clarify if that 2500 range is a rule or not.
In any case thanks very much for your response.