API-6A table 34 was a good start but how to relate API Nominal Bore Size to ANSI B16.34 valves? e.g What is the Nominal Bore Size of a class 300 DN200 gate valve?
Would Table 1 in API 6D not be relevant? 4.4.2 Full-opening valves shall be unobstructed in the fully open position and have an internal minimum circular opening etc etc. I do not believe that B16.34 goes into that area itself.